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ISBN 978-0-626-22040-2 NRS 000-1:2008
Edition: 1
NRS DEFINITIONS Part 1: Compilation of NRS and other definitions used in the Electricity Supply Industry This document is not a South African National Standard
N R S
NRS 000-1:2008
This specification is issued by the Standardization Section, Eskom,
on behalf of the User Group given in the foreword.
Table of changes Change No. Date Text affected
COPYRIGHT RESERVED
Printed in the Republic of South Africa by the SABS Standards Division
1 Dr Lategan Road, Groenkloof, Pretoria
Correspondence to be directed to Printed copies obtainable from The NRS Projects Manager The SABS Standards Division The Industry Association Resource Centre Private Bag X191 Private Bag X13 Halfway House - 1685
Pretoria 0001
Telephone : (011) 651 6832 Telephone : (012) 428-7911 Fax : (011) 651 6827 Fax : (012) 344-1568 E-mail : [email protected] E-mail : [email protected] Website : http://www.nrs.eskom.co.za Website : http://www.sabs.co.za
NRS 000-1:2008
Foreword
This part of NRS 000 was prepared on behalf of the Electricity Suppliers Liaison Committee (ESLC) and approved by it for use by supply authorities.
A reference is made in several definitions to various legislation and regulations. The following table provides details thereof.
Page no. Definitions affected Relevant legislation/regulation
8 appointed operator OHS Act
18 Chief inspector of Machinery OHS Act
20 close proximity OHS Act
22 competent person OHS Act
24 consumer’s supply point OHS Act
31 design tension OHS Act
31 designated person OHS Act
43 experienced person OHS Act
50 ground span
54 insulated OHS Act
64 live work declaration
79 operating authority
79 operating authority form
84 point of control OHS Act
85 point of supply OHS Act
95 regulation
107 specifically trained person OHS Act
108 standard for live work OHS Act
109 standard voltage Electricity Act
111 supervision
111 supplier
119 authority responsible for regulations Post Office Act, 1958 (Act 44 of 1958)
NRS 000-1:2008
This edition supersedes NRS 034-0: 2001 (edition 1.2) and NRS 040-1: 1999 (edition 1.1).
NRS 000 consists of the following parts, under the general title NRS definitions:
Part 1: Compilation of NRS and other definitions used in the Electricity Supply Industry Part 2: Electricity pricing.
Part 3: HV operating regulations
Part 4: Electricity distribution – Guidelines for the provision of electricity distribution networks in residential areas
Introduction
The definitions in this part of NRS 000 have, in general, been drawn from the NRS specifications published up to March 2008 and includes those definitions from NRS 034-0 and NRS 040-1.
This part of NRS 000 consists of terms and definitions extracted from published NRS specifications. Certain definitions have also been included from documents published by Eskom.
The list was compiled as a step towards standardization of terminology. No attempt was made to remove any inconsistencies or conflicting statements. Users are encouraged to select the most appropriate definition from the list.
In some instances there were several options for a single definition, each option being determined by its contextual use. A preferred option is highlighted. Where a definition from an IEC standards was used, it was indicated in squared brackets after the definition. The intention is to use the IEC definition unless there is good reason to modify the definition for a specific application.
Stakeholders of the Electricity Supply Industry are urged to avoid a proliferation of definitions used in the industry by using the definitions contained in this part of NRS 000. It is the intention to revise this part of NRS 000 annually.
1 NRS 000-1:2008
Contents
Page
1 Scope ........................................................................................................................... 3
2 Normative references.................................................................................................... 3
3 Terms and definitions .................................................................................................. 3
2 NRS 000-1:2008
This page intentionally left blank
3 NRS 000-1:2008
NRS DEFINTIONS
Part 1: Compilation of NRS and other definitions used in the Electricity Supply Industry
1 Scope
This part of NRS 000 covers terms and definitions that are used in the Electricity Supply Industry.
2 Normative references
Not applicable.
NOTE However, as indicated in the Introduction, the definitions in this document have, in general, been drawn from NRS specifications published up to March 2008. NRS specifications are accessible on the NRS Website <http://www.nrs.eskom.co.za>.
3 Terms and definitions
For the purposes of this part of NRS 000, the following terms and definitions apply.
“a” contact (make contact) control or auxiliary contact that is closed when the main contacts of the mechanical switching device are closed and open when they are open
a gas turbine set thermal generating set in which the prime mover consists of a gas turbine
a test position (of a withdrawable part) position of a withdrawable part in which an isolating distance or segregation is established in the main circuit and in which the auxiliary circuits are connected
absolute error algebraic difference between the indicated value and a comparison value
absolute error
difference obtained by subtracting the true value of the quantity from the measured value
acceptable acceptable to parties concerned, or acceptable to the customer (depending on the context used)
account card card which, when presented by a customer, automatically identifies the electricity account that the customer has with the electricity distributor
accreditation procedure by which an authoritative body gives formal recognition that a body or person is competent to carry out specific tasks [ISO/IEC Guide 2]
accreditation (of a person) process of verifying that the applicant meets the specified requirements
accreditation (of a laboratory) formal recognition that a testing laboratory is competent to carry out specific tests
4 NRS 000-1:2008
accreditation body body that conducts and administers a laboratory accreditation system and that grants accreditation
accredited calibration laboratory laboratory that has been accredited by the government endorsed national accreditation body (SANAS) in accordance with SANS 17025 for calibration of metering equipment. NOTE Laboratories can be accredited by SANAS anywhere in the world through mutual recognition schemes. accreditation criteria set of requirements that is used by an accreditation body, to be fulfilled by a testing laboratory in order for it to be accredited
accredited laboratory testing laboratory to which accreditation has been granted
accredited laboratory laboratory that has been accredited by SANAS in accordance with [ISO/IEC17025]
accredited test authority authority that is accepted by the South African National Accreditation Service (SANAS)
accredited test laboratory laboratory that has been accredited by the government endorsed national accreditation body (SANAS) in accordance with SANS 17025 for type testing of metering equipment. NOTE Laboratories can be accredited by SANAS anywhere in the world through mutual recognition schemes.
accumulator count of impulses associated with impulse energy metering
accuracy class designation assigned to an instrument transformer, the current or voltage error and phase displacement of which remain within specified limits under prescribed conditions of use. [IEC]
accuracy class category of measuring instruments, all of which are intended to comply with a set of specifications regarding uncertainty
accuracy class index number that gives the limits of the permissible percentage error as defined in the applicable specification for a meter when the meter is tested under reference conditions
NOTE Multi-range and multipurpose instruments may have more than one accuracy class index.
activation date date on which a new tariff or season or year becomes active
NOTE All the rate period totals for the billing month up to the activation date shall be saved and the new
totals created and used for the remaining period of the billing month.
active energy electrical energy transformable into some other form of energy [IEC]
active energy integral of active power with respect to time.
5 NRS 000-1:2008
active energy meter instrument that is intended to measure active energy by integrating active power with respect to time [IEC]
active power under periodic conditions, mean value, taken over one period T of the instantaneous power of p
∫=T
Otp
T
IP d
active power time average of the instantaneous power over one period of the wave, measured and calculated in watts
NOTE In the case of sinusoidal quantities in a two-wire circuit it is the product of the voltage, the current, and the cosine of the phase angle between them. In the case of non-sinusoidal quantities it is the sum of the harmonic components, determined as above. In the case of a polyphase circuit it is the sum of the active powers of the individual phases.
active power transducer transducer for the measurement of the active electrical power
actual transformer ratio ratio of the actual primary current to the actual secondary current
additional customer capacity additional amount of power rated in kVA that a customer requires by increasing his notified or actual maximum demand
addressing of data-points protocol function that supports the addressing of individual data-points or groups of data-points.
NOTE The protocol allows the user to query the current status of an individual, a group or all analogue, digital and counter data-point(s)
addressing of remote terminal units (RTUs) protocol function that supports the unique addressing of devices in any network topology
adjustment operation that is intended to reduce the differences between the values indicated by an instrument and the values realized by a reference standard to within a predetermined tolerance
aerial bundled conductor aerial cable that consists of a group of insulated conductors laid-up together. In the case of a low-voltage aerial bundled conductors (ABC) that uses a supporting core system, the supporting core can be bare or covered (see note). A medium-voltage ABC is supported by a separate steel catenary wire
NOTE Two types of construction of LV ABC are commonly used. One type comprises phase conductors supported by a neutral conductor, which can be bare or insulated. (This type, which is used in France, is commonly referred to as the French ABC system.) The other type of construction comprises conductors that are all equally supported by fittings. (This type of construction, called self-supporting ABC, is used in Germany, and is known as the German ABC system.)
aerial bundled conductor aerial cable that consists of cores twisted together
6 NRS 000-1:2008
aerial bundled conductors aerial cable that consists of a group of insulated conductors laid-up together. In the case of a medium-voltage aerial bundled conductors, conductors are supported by a separate steel catenary wire
after diversity maximum demand simultaneous maximum demand of a group of consumers divided by the number of consumers, expressed in kilovolt amperes
NOTE Characteristic after diversity maximum demand (ADMD): the value of the ADMD in a specific area of supply generally decreases to an approximate constant value for 1 000 consumers or more. This value is known as the characteristic ADMD. Where the ADMD is used with no mention of the number of consumers, it is assumed to be the characteristic ADMD, and is equal to the design ADMD.
airdac service cable suitable for single-phase reticulation and connections NOTE It is specially developed for intermediate voltage use at 1,1 kV. (See concentric cable and split concentric cable.)
air filled enclosure metallic enclosure designed to protect the ends of the cables, bushings, current transformers or live conductors
air insulated termination air filled enclosure within which the cable cores are electrically terminated by stress control appropriate to the cable design and voltage with air being the sole insulation for the terminal connections
air mass numerical value used to give an overall measure of the amount of atmosphere through which solar radiation has to pass. At sea level, when the sun is directly overhead, the air mass is 1,0. When the sun is lower in the sky (some hours from noon, or in winter months), the solar radiation has to cut through more atmosphere and the air mass is then higher than 1,0. [RAPS design manual]
airbreak switch device used for the purpose of connecting, sectionalizing or isolating equipment or sections of overhead line
alive; live electrically charged
algorithm precise and rigorous statement of a method of calculation all aluminium conductor stranded conductor, of which all wires are made of aluminium
all-aluminium alloy conductor (AAAC) stranded conductor of which all wires are made of aluminium alloy [IEC Dictionary] all aluminium conductor, steel reinforced (ACSR) conductor comprising aluminium strands helically wound around steel reinforcing strands (s)
allocation mechanism algorithm or parameters to apportion a cost to different sub-elements
alternating current system electrical system fed by alternating voltage
7 NRS 000-1:2008
alternating current system; a.c. system electrical system fed by alternating voltage [IEC]
aluminium alloy conductor steel reinforced reinforced conductor with one or more layers of aluminium alloy wires stranded around a core of galvanized steel wires
aluminium conductor steel reinforced reinforced conductor with one or more layers of aluminium wires stranded around a core of galvanized steel wires [IEC]
amortization period period over which a future cash flow is converted into an annuity
analog(ue) representation (of a physical quantity): representation of one physical quantity by another physical quantity in which the representing quantity may continuously assume any value between specified limits, when the physical quantity to be represented is varied continuously between corresponding limits
analog(ue) signal signal in the form of a continuously variable value [IEC]
analog(ue) to digital conversion transformation of an analogue quantity into a digital representation by means of sampling, quantization and encoding, and the necessary auxiliary operations
analogue to digital converter electronic device for performing the analogue to digital conversion of electrical signals, and for supplying the converted values in digital electrical form
analogue control protocol function that supports the issuing of analogue outputs on the slave NOTE (For example the level setting of analogue loop outputs or the level of the voltage output pulse)
analogue signal signal in which the characteristic quantity representing information may at any instant assume any value within a continuous interval
anchor device, usually buried in the ground , so installed as to provide a firm point of attachment for resisting upliftment.
anchor rod rod or other metallic element, connecting the stay, or guy, to the anchor [IEC]
aniline point temperature at which the oil becomes a solvent and gives an indication of the level of refining
annualized cost single cash flow converted into an annuity with an equal present worth
anti-climbing device device installed on, or attached to, a support, structure, tower, guy, etc., to prevent climbing by unauthorized persons
apparatus electrical appliance, machinery, switchgear, feeder, plant or electrified fencing that forms part of a system
apparatus transformer, motor, circuit-breaker, switch, link, feeder, test equipment, electrified fence or any other LV/MV/HV plant installed in a substation, feeder or system
8 NRS 000-1:2008
apparatus general term used for designating instruments , detectors, assemblies, sub-assemblies and components
apparatus device or assembly of devices which can be used as an independent unit for specific functions
apparent power product of the measured root mean square (r.m.s.) a.c. current and the measured (r.m.s.) a.c. voltage, expressed in volt-amperes (VA)
apparent power product of the r.m.s voltage U, between the terminals of a two-terminal element or a two-terminal circuit and the r.m.s electric current I, in the element or the circuit: S=UI
apparent power square root of the sum of the squares of the active and reactive powers, measured and calculated in volt-ampere, for sinusoidal quantities in either single phase or polyphase circuits
NOTE This is, in general, not true for non-sinusoidal quantities.
appointed operator employee who has been authorized in writing to carry out switching, isolating, safety testing and earthing operations in terms of the relevant HV Operating Regulations
apportioned share of incremental costs share calculated by a particular method, based on the additional capacity required, of the incremental costs which is required to supply the particular applicant
approval process of obtaining approval from the Regulator to provide services based on compliance with specified requirements
NOTE The accreditation of an applicant should precede the process of granting approval.
approval; approved with the approval of (or approved by), the purchaser, in writing
approved acceptable to and approved, in writing, by purchaser
approved given approval in writing by the supplier or its authorized representative
approved acceptable to, and approved in writing by, the person in charge of the system
approved laboratory laboratory approved by the Regulator
approved/approval approved in writing by the purchaser
archived data data from the operational metering database that was saved/stored on a storage medium NOTE For example tape-drives or compact discs
arcing distance shortest distance in air external to the insulator between the metallic parts which normally have the operating voltage between them [IEC]
9 NRS 000-1:2008
arithmetic simultaneous demand simultaneous demand (SD) obtained by addition of the magnitudes of the kilowatt or kilovolt-ampere values for one group of supply points for each integrating period
armour
covering consisting of metal tape(s) or wires, generally used to protect the cable from external mechanical effects
armour layer of wires applied to a cable to provide mechanical protection or earth continuity, or both
armour clamp fitting for gripping the armour of a cable at its termination to the gland body, and capable of retaining the armour in position for fault currents within the design parameters
armoured cable cable provided with a wrapping of metal (usually tape or wire) for the purpose of mechanical protection
NOTE The armour can itself be covered with a protective sheath or serving.
armoured cable cable that contains metallic armouring elements assessed level level used to evaluate the measured values at a particular site against the compatibility levels. NOTE The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points.
asynchronous link interconnection between two a.c. systems operating at independent frequencies
attended substation substation which is operated by personnel during the normal working hours and otherwise as necessary
audit process of inspecting the procedures, facilities and other relevant items to confirm compliance with requirements
audit systematic and independent examination to determine whether the activities and results comply with planned arrangements and whether these arrangements are effectively implemented and are suitable to achieve reliability performance and maintainability performance objectives
audited process of being subjected to an audit
authentication process used between a sender and a receiver, to ensure data integrity and origin integrity authority either a supply authority or a telecommunication authority
authorized capacity capacity per point of supply/stand that has been provided and paid for by the customer/developer. This will at least be the capacity according to the approved zoning but could be higher as notified, requested, agreed and paid
10 NRS 000-1:2008
authorized maximum demand (AMD) maximum load that the customer is authorized by the licensee to take from that point of supply (POS)
authorized maximum demand (AMD) maximum demand, requested in advance by the consumer and authorized by the supply undertaking under the terms of an agreement, for which the supply capacity is made available
authorized operation operation authorized by the system controller or superintendent
authorized person person who has been granted, in writing, defined authority and responsibilities by the designated person in terms of the relevant operating regulations
authorized person person who has been authorized, in writing, with defined authority and responsibilities
automatic reclosing automatic reclosing of a circuit-breaker associated with a faulted section of a network after an interval of time which permits that section to recover from a transient fault
auto-recloser mechanical switching device that, after opening, is capable of closing automatically after a predetermined time; several reclosers could occur before lock-out
auxiliary circuit (of a relay) whole of the electrical parts within a relay(including those parts, if any, intentionally coupled by inductive and capacitive means) and which are connected to those terminals to which a given auxiliary energizing quantity is applied
auxiliary circuit (of a meter) elements (lamps, contacts, etc.) and connections of an auxiliary device within the meter case that are intended to be connected to an external device, for example a clock, a relay, an impulse counter [SANS 62052-11]
auxiliary circuit circuit carrying the current of the auxiliaries such as the compressors and the fans
auxiliary power supply power supply that energizes the auxiliary circuit
auxiliary switchboard panel (or a cubicle) on which are fixed the devices necessary to control, to protect and to distribute auxiliary a.c. and d.c. supplies within a substation [IEC]
auxiliary transformer in a substation, a transformer intended to provide supply to the auxiliary equipment [IEC]
auxiliary transformer of a unit transformer supplying auxiliaries of a unit (of a power station)
availability ability of an item to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval, assuming that the required external resources are provided
availability state of an item of being able to perform its required function [IEC]
11 NRS 000-1:2008
average capital contribution amount of contribution obtained by multiplying the additional capacity required by an applicant by the capital contribution standard charges
average costing costing based upon the average input cost per unit of output
average load total kilowatt-hours or kilovolt-ampere hours divided by a selected time in hours
average power factor kilowatt hours divided by kilovolt amperes multiplied by 1 divided by T where T is the integration period in hours (see portable working standard)
axis each pole is defined by two axes, a major axis and a minor axis, which cross through the pole's centre of gravity
“b” contact (break contact) control or auxiliary contact that is open when the main contacts of the mechanical switching device are closed and closed when they are open back up protection protection equipment or system which is intended to operate when a system fault is not cleared in due time because of inability or failure of the main protection to operate, or in the case of failure to operate of a circuit-breaker other than the associated circuit-breaker [IEC]
backfill (imported) soil or other material placed in an excavation after the installation of the foundation, when the original soil is unsuitable
back-up data replica database of the on-line available data that can be used in case of emergency when the on-line available database fails or gets corrupted
back-up meter additional meter installed on the same primary plant as the main meter for the purpose of storing backup data in the event of failure of the main meter NOTE 1 See main metering which states: a dedicated metering system with one active energy meter, and, depending on the tariff in use, one reactive energy meter and one recorder (where applicable)
NOTE 2 This assembly of meters is fed from one dedicated current instrument transformer core and one dedicated voltage instrument transformer winding.
barcode machine-readable code in the form of a pattern of parallel lines of varying widths, printed on a commodity and used to identify such for stock control purposes bare conductor conductor without any insulating covering
bar-primary current transformer current transformer where the primary winding is a straight bar-type primary conductor passing centrally through the core
backfill soil removed during excavation and re-installed after the installation of the foundation [IEC]
12 NRS 000-1:2008
barrier part providing protection against direct contact from any usual direction of access
barrier earthed metallic cover, or an insulating cover, over live equipment parts that prevents an authorized person from inadvertently coming into contact with the live parts
barrier/barricade
device designed to restrict approach to live electrical apparatus, excavations or other dangerous conditions
base load set generating set whose purpose is to run on continuous duty under operating conditions approaching full load for as long as that operation mode is economical [IEC]
basic current value of current in accordance with which the relevant performance of a direct connected meter is fixed
basic current (Ib) r.m.s. value of current in accordance with which the relevant performance of a direct connected meter is fixed [IEC]
basic insulation insulation that is applied to live parts to provide basic protection against electric shock [IEC]
NOTE Basic insulation does not necessarily include insulation used exclusively for functional purposes.
basic insulation level specific insulation level, expressed in kilovolts, in accordance with which the complete system (including the line pole insulation to earth at every pole, the switchgear, the line isolators and reclosers, and the substations connected to the system, including their transformers) is designed and constructed
basic insulation level (BIL); basic lightning impulse specific insulation level, expressed in kilovolts, that is equal to the crest value of a standard lightning impulse
NOTE The BIL can refer to a complete system, such as a distribution network (including the line pole insulation to earth at every pole, the switchgear, the line isolators and reclosers, and the substations connected to the system, including their transformers) or to a single piece of equipment. Where the BIL is declared by a manufacturer as the impulse voltage level for which the equipment is designed, it is often referred to as the rated insulation level, or rated lightning impulse withstand voltage.
battery powered earth fault indicator earth fault indicator that is powered by means of a disposable battery
baulk concrete beam, attached, in a horizontal position, to the pole at a point or at points below ground level, to improve the stability of the pole under conditions where it is not practicable or possible to use stays
bay (of a substation) part of a substation within which the switchgear and controlgear relating to a given circuit is contained
NOTE According to the type of circuit , a substation may include: feeder bays, transformer bays, bus coupler bays, etc.
13 NRS 000-1:2008
bay processor BP intelligent electronic device (IED) that operates within either a protection bay or a system control and data acquisition (SCADA) switch bay in a substation bedding cushioning layer or layers applied to a cable immediately beneath a metallic layer such as the armour or the reinforcement [IEC]
bedding layer of extruded compound applied to a cable to form a circular base beneath the armour in order to prevent damage to the insulation by the armour
bedding; undersheath cushioning layer or layers applied to a cable immediately beneath a metallic layer such as the armour or the reinforcement
benchmarks default technical losses at various voltage levels or profiles to be used by a utility in the absence of better information
benefit of diversity result of the operation of totalization and the possible flattening of the load curve, that has an inherent benefit to the customers' maximum demand charge
benefit of diversity benefit granted to a consumer where electricity is supplied to a consumer at more than one point of delivery and the maximum demand charged for is the simultaneous maximum demand (co-incident in time) for all points rather than the sum of the individual demands
beta distribution statistical distribution function that can be used to describe the electrical load of a group of consumers at any given time
bidirectional metering meter that can measure import and export active energy and/or leading and lagging reactive energy
billing process of producing and delivering a bill (an account) for payment by a customer, calculated from the tariff schedule, and for the majority of customers, the consumption measured and recorded by the metering system [SANS 62051]
NOTE Bills are also calculated on estimated consumption and for unmetered installations. Customers are billed at regular cycles (e.g. monthly, bimonthly, quarterly or yearly) and when an account is finalized or when a special reading is requested.
billing month time period over which the energy registers are accumulated before they are used to generate a bill. The billing month does not necessarily correspond to a calendar month
billing period time between consecutive billing dates, nominally in months (e.g. one, three or six months) but in practice defined as a number of days (e.g. 28 days, 60 days, 91 days etc.,) [IEC]
binary element group of statements, each being realised by a digital signal, to represent information in digital electrical form
14 NRS 000-1:2008
NOTE The meaning of each statement is determined by the code of the system and is represented by the position in time (or space) of the corresponding signal values. Each statement consists of either a logical "one" or a logical "zero", corresponding to the "one" level state or the "zero" level state of the representing signal. Each of these two values constitutes a binary element, and is represented by a binary digit, or bit.
binder (of a disc) resinous material which serves to bind the various component materials of a disk
binder (of a cable) layer incorporated in a cable with the specific function of holding the components of the cable together within the layer
bipolar d.c. link link having two poles normally operating at d.c. voltages of opposite polarity in relation to earth
birdcaging loosening and separation of the outer layer wires from the inner wires
blank module new secure module that has not been registered at the Eskom key management centre
NOTE A blank module has not been loaded with master keys or vending keys. blinding selected fine material used to completely cover an underground cable or pipe
block symbol simple graphical symbol, representing an assembly of items and intended to indicate the function of the assembly, neither giving details about the items nor taking account of all connections
NOTE Block symbols are generally used in diagrams where a single-line representation is applied. They may also be used in diagrams with all input connections shown.
blocking diode diode (usually Schottky) used to prevent battery discharge through the photovoltaic (PV) array at night
NOTE 1 The blocking diode will also prevent damage to the regulator if the PV array is short circuited.
NOTE 2 Blocking diodes are normally used in PV systems where the nominal voltage exceeds 24 V.
blown tube for fibre optic core tube inserted in the centre of a pilot cable for the purpose of housing optical fibre(s)
boiler installation whose function is to vaporize water under pressure, to superheat and, in some cases, reheat the steam [IEC]
bolted-type separable connector separable connector in which the electrical contact is made by a bolted device
bonding low-impedance interconnection of conductor and equipment, to form an equipotential platform
branch joint accessory that connects a branch cable to a main cable [IEV 461-11-07, modified]
branch line (spur) electric line connected to a main line at a point on its route
NOTE A branch line which is in a final circuit is called a spur.
branch line; spur feeder electric line connected to a main line at a point on its route [IEC]
NOTE A branch line which is a final circuit is called a spur.
15 NRS 000-1:2008
breaker; circuit-breaker mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal conditions, such as those of a short circuit [IEC]
breaking force tensile load applied during testing, under which a cable finally breaks or becomes permanently deformed
breaking load load in newtons (N), that a material, component or device will resist before it breaks
breaking load tensile load applied during testing, and at which the cable breaks or becomes permanently deformed
broadcast facility protocol facility that provides for the distribution of one message to more than one recipient, group of slaves or all the slaves in the network. NOTE Recipients include, amongst others, remote terminal units (RTUs) masters and submasters
bulk supply supply to a consumer's substation at a voltage of 80 kV or higher
burden value of the impedance of the secondary circuit expressed in ohms (or in volts per ampere at the rated secondary current) at the relevant power factor
burden (of an instrument transformer) impedance of the secondary circuit [IEC]
NOTE The burden is usually expressed as the apparent power absorbed by the secondary circuit at a specified power factor at the rated secondary current or voltage.
burying depth specified depth at which a cable is to be buried NOTE This shall be a minimum of 500 mm.
bus coupler apparatus used for connecting two sets of busbar bus coupler circuit-breaker designed to connect or disconnect two busbar sections in parallel
bus coupler circuit-breaker in a substation a circuit-breaker which is located between two busbars and which permits the busbars to be coupled; it may be associated with selectors in case of more than two busbars [IEC]
bus section breaker apparatus used for connecting two sections of the same busbar bus section circuit-breaker circuit-breaker designed to connect or disconnect two busbar sections in series
bus-coupler switchgear panel
bus-section switchgear panel switchgear panel that is used to open and close the electrical connection and provide safety isolation between two busbar systems of a switchboard with a double busbar configuration NOTE It could include a switch-disconnector or a circuit-breaker.
16 NRS 000-1:2008
bus section isolator isolator designed to connect or disconnect two busbar sections in series
busbar low impedance conductor to which several electric circuits can be separately connected [IEC]
bushing device that enables one or several conductors to pass through a partition such as wall or a tank, and insulates the conductors from it. The means of attachment (flange or fixing device) to the partition forms part of the bushing
NOTE 1 The conductor may form an integral part of the bushing or may be drawn into the central tube of the bushing.
NOTE 2 The bushings may be of the following types: liquid filled bushing; liquid insulated bushing; gas filled bushing, gas insulated bushing; oil impregnated paper bushing; resin bonded paper bushing; resin impregnated paper bushing ; ceramic, glass or analogous inorganic material bushing; cast insulation bushing ; composite bushing
bushing structure carrying one or more conductors through a partition (such as a wall or tank) and insulating it there from, including the means of attachment (flange or other fixing device) to the partition
bus-section; bus-coupler switchgear panel switchgear panel that is used to open and close the electrical connection and provide safety isolation between two sections of busbar of the switchboard
NOTE 1 The bus-section switchgear panel may include a switch-disconnector or a withdrawable circuit-breaker.
NOTE 2 In a double busbar configuration, a bus-section switch opens or closes the electrical connection between two sections of the same busbar, or of the top and bottom busbar sections, or of the front and rear busbar sections. A bus-coupler switch is used only on a double busbar configuration and opens or closes the electrical connection between the two busbar systems, or, alternatively, between the top and bottom or
the front and rear busbar systems.
bypass diode diode used to prevent damage to the photovoltaic module under partial shade conditions
cable feeder, normally underground, including its terminations
cable length of one or more insulated conductors with or without an overall protective covering
cable assembly of one or more conductors or optical fibres or both, with a protective covering and possibly filling, insulating and protective material
cable length of one or more cores with an overall protective covering
cable gland device to seal and secure the sheath and to secure the armour (where provided) of an electric cable to the terminal equipment by means suitable for the type of the cable for which it is designed, including provision for making an electrical connection to the sheath and to the armour
cable termination box cable termination enclosure that can be used for either single-core or three-core cables
cable tie component that has the specific purpose of holding together the cable cores which it surrounds
17 NRS 000-1:2008
cable wiping gland cable gland that has a wiping gland body
cable (superconductivity-related technology) conductor which consists of two or more wires
NOTE A cable or individual strands which may or may not be covered by an electrical insulation
calibration set of operations that establishes, by reference to standards, the relationship which exists, under specified conditions, between an indication and a result of measurement
calibration set of operations that establishes, under specified conditions, the relationship between the values indicated by a measuring system and the corresponding values of a quantity realised by a reference standard or a working standard
calibration report report that contains the results of all calibration tests carried out on a metering installation or a component of a metering installation by an approved laboratory as part of the certification process
capacitor voltage transformer voltage transformer comprising a capacitor divider unit and an electromagnetic unit so designed and interconnected that the secondary voltage of the electromagnetic unit is substantially proportional to the primary voltage, and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections
capacitor voltage transformer CVT voltage transformer that comprises a capacitor divider unit and an electromagnetic unit so designed and interconnected that the secondary voltage of the electromagnetic unit is substantially proportional to and in phase with the primary voltage applied to the capacitor divider circuit
capital charges all charges raised towards covering the network capital costs including: connection fees, monthly capital charges and up front capital contributions but excluding charges contained in the monthly tariffs
capital contributions once off contributions made by customers/developers towards the capital costs of networks installed by the utility to meet the customer/developers electricity needs
capital contributions cash contributions made by customers towards the capital cost of networks installed by the utility on behalf of the customer
capital contributions due highest of the average capital contribution and the apportioned share of incremental costs plus the dedicated costs
NOTE 1 Incremental costs are capital costs, incurred at the time of development.
NOTE 2 Dedicated costs are the total capital costs associated with a particular customer only.
capital contribution rebates amounts deducted from the capital charges due or repaid to a developer because of work done by or materials provided by a developer or customer considered not part of their contributions
capital contribution standard charges charges calculated to represent the average capital costs per unit of various networks in the utility
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capital contribution subsidies situations where the required capital contribution is funded by another party than the one to whom it is due
capital rate non-escalating monthly capital repayment rate applied to the capital contribution due to the conversion to a monthly capital charge
capless line post insulator rigid insulator that consists of one or more insulating parts with metal insert, and intended to be mounted rigidly on a supporting structure by means of a spindle
NOTE The definition for capless line post insulators differs from one in IEC 60383-1: this definition is applicable to a line post insulator without a cast iron cap.
capped line post insulator rigid insulator that consists of one or more insulating parts with metal base and sometimes a cap intended to be mounted rigidly on a supporting structure with the metal base attached by means of a stud or one of several bolts
carrier frequency coupling device circuit element that is intended to permit the injection of carrier frequency current, and that is connected between the low-voltage terminal of a capacitor divider unit and earth
NOTE The coupling device has an impedance that is insignificant at power frequency but appreciable at the carrier frequency.
certification procedure by which a third party gives written assurance that a product, process or service conforms to specified requirements [ISO/IEC Guide 2] certification confirmation that the whole metering system is installed and functioning correctly, and that the metering installation and its individual components comply with the overall accuracy limits and component standards
certification report report that contains the calibration report and other information relevant to the certification of a metering installation or a component thereof
certified test report certificate that gives evidence of compliance with requirements given in the specification where testing for these requirements was carried out by a recognized authority
chamber enclosure in which high voltage apparatus is separated from other apparatus by partition walls or other means and the access to which is restricted by interlocks
channel (metering) input or a register for raw data that corresponds to a specific meter
NOTE If the encoder has built-in meters, the meter is considered to have four channels with values corresponding to kilowatt-hours (import and export) and kilovar-hours (leading and lagging).
channel load profile data corresponding to one of the measurands such as kWh or kVAh
channel multiplier constant by which the channel readings are multiplied in order to obtain engineering units
19 NRS 000-1:2008
character member of a set of elements used by agreement, for the organization, representation or control of information
NOTE Characters may be letters, digits, punctuation marks or other symbols and, by extension, functions controls such as space shift, carriage return or line feed contained in a message.
character member of the set of elements that is intended for use in conveying information, either when arranged together in an agreed fashion, or when isolated
check metering dual-redundant metering system (a completely separate installation) that has two dedicated current transformer (CT) cores but may have only one dedicated voltage transformer (VT) winding
Chief Inspector of Machinery chief inspector appointed by the Minister of Labour in terms of the Occupational Health and Safety (OHS) Act, 1993 (Act 85 of 1993)
child key key that is encrypted with a parent key
cipher method of cryptography that applies an algorithm to the letters or digits of the plaintext to create cipher text, and vice versa
NOTE Typically the algorithm is used in conjunction with one or more keys.
circuit conductor or a system of conductors through which an electric current is intended to flow
circuit arrangement of conductors for the purpose of carrying electrical energy
circuit earth that part of a circuit that is or can be connected directly to earth
circuit-breaker mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions, such as those of a short-circuit [IEC]
circuit-breaker class B circuit-breaker so designed as to not require maintenance of the interrupting parts of the main circuit during the expected operating life of the circuit-breaker, and only minimal maintenance of its other parts
NOTE Minimal maintenance might include aspects such as lubrication, replenishment of gas, and cleaning of external surfaces. circuit-breaker panel switchgear panel complete with a fixed or withdrawable circuit-breaker circuit-side side of a circuit-breaker or switch that contains the cable or circuit connections, and that can be isolated from the busbars
20 NRS 000-1:2008
cladding dielectric material of an optical fibre surrounding the core
clamping voltage voltage that is maintained between the terminals of an arrester during the passage of the discharge current, and that determines the protective characteristics of the arrester
clamping voltage see residual voltage
class A insulator insulator or insulator unit in which the length of the shortest puncture path through solid insulating material is at least equal to half the arcing distance
NOTE An example of a class A insulator is a long rod insulator with external fittings.
class designation maximum of the load range in amperes. (see load range which states: the maximum range in amperes over which the meter is designed to operate continuously with a specified accuracy under certain conditions)
NOTE This is usually applicable to meters of American origin.(see load range)
class index conventional designation of an accuracy class by a number or symbol
class index see accuracy class index, which states: a number that gives the limits of the permissible percentage error as defined in the applicable specification for a meter when the meter is tested under reference conditions
NOTE Multi-range and multipurpose instruments may have more than one accuracy class index
clean up action of remediation that includes soil excavation, bioremediation, solvent soil wash, land farming or electrochemical treatment
clearance distance between two conductive parts along a string stretched the shortest way between these conductive parts
clearance shortest distance between two conductive parts.
NOTE 1 In this code of practice the term “clearance” or “safety clearance” is used to specify the minimum distance between a live part and an object for the safety of persons. Where reference is made to a specific type of safety clearance the terms “working clearance” or “live-line working clearance”, as applicable, are used.
NOTE 2 For the philosophy behind safety clearances as applicable to this code of practice.
clearance shortest distance through air or through an insulating fluid or semi-fluid between two conductive parts
clearance shortest distance between two conductive parts, usually related to distance in air
a) activity clearance sum of the personal reach and the length of a hand-held object
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b) electrical clearance
distance in air between live parts and earthed material or between live parts at different potentials which serves as protection against electrical breakdown
NOTE In generic terms, the electrical component of the minimum working distance between two electrodes is required to prevent sparkover under the most severe electrical stress that will arise under the chosen conditions.
c) object clearance
sum of the uncertainty and activity clearances
d) safe clearance sum of the electrical and uncertainty clearances
e) uncertainty clearance
additional distance stipulated by the supply authority to allow for uncertainty
f) working clearance straight-line distance between the live part and the position of the person working on the electrical system
NOTE The working space is the region within the boundary of the working clearance where a person can safely work on dead equipment.
clearance to earth clearance between any conductive parts and any parts which are earthed or intended to be earthed
close proximity a position in which a part of a person or part of a tool being used could inadvertently encroach within the minimum safe clearance (of any bare, live parts) according to the OHS Act
close proximity beyond a position in which any part of a person or tool being used could inadvertently encroach within the minimum safe clearance (of any bare, live parts) according to the OHS Act, 1993
closed loop breaking current breaking current when opening a closed loop circuit, i.e. a circuit in which both sides of the switch remain alive after breaking and in which the voltage appearing across the terminals is substantially less than the system voltage [IEC]
closing closing of a circuit-breaker by either manual or automatic control of protective devices [IEC]
NOTE The expression "closing" of a network item (line, transformer) in fact means closing of the
associated circuit-breakers.
code set of rules defining a one-to-one correspondence between information and its representation by characters, symbols or signal elements
code agreed set of unambiguous rules to specify the way in which data may be represented by the characters of a character set
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coded module secure module initialized and loaded with the vending keys of specific supply group codes
NOTE A coded module has been loaded both with master keys and vending keys. code of practice document that recommends practices or procedures for the design, manufacture, installation, maintenance or utilization of equipment, structures or products. [ISO/IEC Guide 2].
NOTE A code of practice can be a standard, a part of a standard or independent of a standard.
coincidence factor (CF) way to describe diversity
NOTE CF is equal to the inverse of the diversity.
0 and DF(N)
1 = CF(N) < CF < 1 and CF = 1 for one customer
i.e. CF is always between 0 and 1, except for one customer when it is equal to 1.
cold load pick-up feature feature that allows modification of the overcurrent protection characteristics in order to prevent relay maloperation under conditions of system energization
cold reserve
total available capacity of generating sets in reserve for which the starting up may take several hours [IEC]
cold start-up of a thermal generating set process by which the generating set is raised to speed, the machine connected to the system and loaded after a long period of being out of operation [IEC]
coloured coating thin coating applied on the primary coating in order to make each fibre distinguishable by its colour
combined neutral and earth conductor that combines the functions of a neutral conductor and an earth conductor
commissioning formal procedure for the addition of apparatus or systems to the existing system
common auxiliaries group of auxiliary equipment which is common to the unit and the power station
common group see common supply group common mode (CM) voltage mean of the voltages appearing between each conductor and a specified reference, usually earth or frame common supply group supply group that associates a set of electricity dispensers on a geographical or regional basis, in which each and every electricity dispenser in the supply group has a common dispenser key communication core insulated solid wire that is intended to carry data
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communication data link means of communication between two or more electronic devices, using a defined protocol
communication lines lines that convey information by electrical means, specifically excluding optical fibre
communication media physical communication media supported by the protocol NOTE (e.g. radio, keyed radio transmissions; telephone dial-up modem)
compact switchgear switchgear where the overall dimensions are reduced due to enhanced insulation (for example gas insulation)
NOTE The reduction in the width of the panels is most desirable.
compacted conductor stranded conductor in which the interstices between the component wires have been reduced by mechanical compression, or by drawing, or by suitable choice of the shape and disposition of wires
compatibility level (electromagnetic compatibility level) specified disturbance level at which an acceptable, high probability of electromagnetic compatibility should exist [IEC]
NOTE Quality of supply (QOS) is described by a particular set of electromagnetic compatibility levels. These compatibility levels are used to set minimum standards. It follows that the compatibility level should be so chosen that the equipment connected to the supply network has a high probability of operating correctly, and that the supply network has a high probability of operating within the required limits.
compatibility level (electromagnetic) specified electromagnetic disturbance level used as a reference level for coordination in the setting of emission and immunity levels
competent person person who complies with section A.1 (vii) of the OHS Act, 1993, and is in possession of a competency certificate for the classes of work in which he is deemed to be competent to work without constant supervision
competent person person that complies with the appropriate sections of the Occupational Health and Safety Act, 1993 (Act No. 85 of 1993) and is in possession of a competency certificate for the classes of work in which he is deemed to be competent to work without constant supervision completely self-protected (CSP) transformer transformer that is designed to be self-protected against overloads, short-circuits and overheating
compliance testing (of a metering installation) procedure whereby a metering installation and its component parts are proved to comply with applicable requirements NOTE The procedure includes the issuing of a compliance report.
composite cable cable containing both elements of copper and optical fibre
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composite insulator insulator made of at least two insulating materials; the core and the external envelope. The composite insulator, for example, can consist either of individual sheds mounted on the core, with or without an intermediate sheath or alternatively, of the complete envelope with sheds directly moulded or cast in one piece on the core
composite insulator insulator that consists of at least two insulating parts, a core part and a housing part equipped with fittings
NOTE A composite insulator, for example, can consist either of individual shed mounted on the core, with or without an intermediate sheath, or alternatively, of a housing directly moulded or cast in one or several pieces on to the core.
compression jointing; crimped jointing method of securing a connector to a conductor by using a special tool to produce permanent deformation of the connector and the conductor
concentric cable sheathed cable that has a phase core surrounded by a neutral-earth conductor that forms a single concentric layer around the phase core
concentric cable sheathed cable that has an insulated phase conductor surrounded by a neutral-earth conductor that forms a concentric layer around the phase conductor conductor any wire, bar or tube intended to conduct electric current
NOTE A conductor usually consists of a single, or bundle of, flexible metallic, copper or aluminium strand(s).
conductor part of a cable having the specific function of carrying current
NOTE A conductor usually consists of a single, or bundle of, flexible metallic, copper or aluminium strand(s).
conductor conductive part intended to carry a specified electric current
conductor insulation insulation applied on a conductor or on a conductor screen [IEC]
conductor size nominal cross-sectional area of a conductor
conductor(cable) part of a cable which has the specific function of carrying current
conduit protective metal or plastic pipe to contain wires
conduit
part of a closed wiring system of generally circular cross section for insulated conductors or cables in electrical or communication installations (or both), allowing them to be drawn in and/or replaced
connecting length physical length of the insulator or insulator string measured between its attachment points at either end
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connection fees standard minimum up front fee payable by the customer towards the cost of a new connection
connector component that terminates conductors for the purpose of providing connection and disconnection to a suitable mating component [IEC]
connector fitting providing mechanical connection between two electrical conductors
connector metallic device that connects cable conductors. [IEV 461-17-03], modified
connector device that has a barrel or socket at one end or at both ends, for connecting a conductor to an equipment terminal or for connecting two or more conductors
connector device providing connection and disconnection to a suitable mating component
consensus general agreement characterized by the absence of sustained opposition to substantial issues by any important part of the concerned interests and by a process that involves attempting to take into account the views of all parties concerned and to reconcile any conflicting views
consolidated edition edition of a specification in which all approved amendments and technical corrigenda have been incorporated. The consolidation will be reflected in the incremented edition number that will reflect the year(s) of publication of the amendments and corrigenda and the publication date of the base document
constant force spring strip of non-magnetic stainless steel that is wound to form a spring and that is intended to maintain a constant force on a circular object
construction supervisor person with on-site control of construction
consumer person who is supplied (or who is to be supplied) with electricity by an electricity supplier
consumer
user of electricity provided by an electricity supply system, generally a distribution system [IEC]
consumer party who receives electricity from the supply or distribution undertaking
consumer’s earth terminal clamp or terminal at the point of supply by means of which the exposed conductive parts of the consumer’s installation are connected to an earth electrode or to the supplier’s protective conductor. A terminal fitted on equipment and providing a means of connection for an earth conductor [IEC]
consumer’s installation electrical apparatus under the control of a consumer on the consumer’s premises
consumer’s supply point see point of supply, which states: the point at which electricity is supplied to any premises by a supplier. [Regulation R1, OHS Act]
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consumer's substation substation owned and operated by a consumer to distribute electrical energy around his premises
NOTE The electricity supply authority responsibility ends at the point of supply.
consumption energy used by a customer during a specific period, measured in kWh
continuous current of an arrester current flowing through the arrester when energized at the continuous operating voltage [IEC]
contractor (revenue protection contractor) company or organization that provides revenue protection services for a supplier
control board (desk) board (desk) on which are fixed control devices which are necessary to control and display a substation or a system [IEC]
control cable multicore cable for the transmission of control, measuring and indication signals in electric installations control centre place from where the safe operation of the generation, transmission and distribution of electric power to customers is controlled or directed (or both)
control centre (controlling station) station which performs the telecontrol of outstations. The place where a master station is located.
control centre master station central station responsible for the monitoring and control of an electricity utility power network control officer; controller employee or official on duty at a control centre, who is responsible for the general operation of the power system, or of a section thereof
control panel panel incorporating all the control means necessary for the operation of a signalling installation, with or without corresponding indications
control panel; panel panel on which control switches and other equipment are mounted for controlling the operation of the apparatus
control panel; panel panel on which are mounted control switches and other equipment for controlling the operation of the apparatus are mounted
control range range of values defined by the two extreme values within which the controlled variable can vary under specified operating conditions
control range (of a generating set) specified range of active power within which a power-controlled generating set must be able to operate [IEC]
control switch switch or device that controls the operation of a breaker, switch, isolator or other apparatus
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control switch (control and auxiliary circuits) mechanical switching device which serves the purpose of controlling the operation of the switchgear or controlgear, including signalling, electrical interlocking, etc.
controllable load load of particular consumers which, under contract, must be reduced for a limited period of time, at the request of the distribution supply undertaking [IEC]
controllable set generating set whose purpose is to run at load levels varying according to the needs of the network supplied as long as that operational mode is economical [IEC]
controller employee or official on duty at a control centre, who is responsible for the general operation of the power system or of a section thereof conventional switching (lightning) peak value of a switching (lightning) impulse test voltage at which an insulation shall not show any disruptive discharge when subjected to a specified number of applications of this impulse under specified conditions [IEC]
NOTE This concept applies particularly to non-self-restoring insulations.
conversion of electricity changing of the characteristics of the form and frequency of voltage and current by means of a converter [IEC]
conversion fees minimum up front contribution payable when there are tariff changes, meter changes, changes in installation or when a supply point is shifted
converter substation substation including converters and the main function of which is to convert alternating current into direct current or vice versa [IEC]
core single insulated conductor without an overall protective covering
core parts of a magnetic circuit in a machine, excluding the air-gap, which are intended to carry the magnetic flux
core central region of an optical fibre through which most of the optical power is transmitted
core assembly that comprises a conductor with its own insulation (and screen, if any) core central region of an optical fibre, generally with higher refractive index than the surrounding cladding resin coating applied directly to the cladding, usually at the time of the fibre drawing, in one or more layers, to preserve the integrity of the cladding surface
core (of a composite insulator) internal insulating part of a composite insulator design to ensure the mechanical characteristics The core usually consists of glass fibres which are positioned in a resin-based matrix.
core; insulated conductor assembly comprising a conductor with its own insulation
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corrosive sulfur sulfur that contains molecules that have negative effects on oil and can cause corrosion problems in power equipment
cost pooling cases where the cost of a network is pooled for various customer categories for the purpose of determining charges
cost of services cost of services includes all direct costs incurred by the utility to supply electricity plus indirect costs such as profits, taxes, subsidies and abnormal costs
cost sharing cases where costs are pooled and shared between the customers taking supply from the network
cost vs. price cost is the amount of money incurred by the utility to supply a unit of goods or service. Price is the amount of cash paid by the customer to a utility for a unit of goods or service
cost-of-supply methodology standard procedure based upon a selected philosophy that is used to derive and allocate the costs of supplying electrical energy to various customer categories
countable events particular events such as over current, earth fault and sensitive earth fault that are accumulated on the counts-to-open counter
counter see accumulator, which states: a count of impulses associated with impulse energy metering
counter sequential circuit in which a number is stored and to which a constant integer number is added algebraically depending on a switching variable at the counter input
covered conductor conductor for use on overhead electrical distribution lines, that is covered with a thin layer of insulation, insufficient to provide full insulation for the applied voltage
credit dispensing unit device used in the vending process to physically carry out the sale of electricity to the customer through the encoding of a token or a receipt (or both)
NOTE 1 A credit dispensing unit (CDU) can vend (dispense) different types of tokens (credit, reset, current limit, etc.).
NOTE 2 A CDU will contain a token encryption device (TED) and a token issuing device (TID).
creepage distance r.m.s. value of sinusoidal voltage at rated frequency applied to the secondary terminals of the transformer, all other windings being open-circuited, which, when increased by 10 %, causes the r.m.s. value of the excitation current to increase by 50 % [IEC]
creepage distance shortest distance, along the surface of the insulating material, between two conductive parts [IEC]
creepage distance shortest distance or sum of the shortest distances measured along the contours of the external surfaces of the insulating parts between those parts of an insulator which normally have the operating voltage between them
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crimped jointing see compression jointing, which states: a method of securing a connector to a conductor by using a special tool to produce permanent deformation of the connector and the conductor
cross-arm component of a pole structure, usually horizontal, to which the line insulators are attached to provide the required clearance distance
crossing span of a network where it crosses over a road, river, railway, telecommunication or other service
cryptographic key parameter used in conjunction with an algorithm for the purposes of validation, authentication, encipherment or decipherment
cryptography discipline that embodies the principles, means and methods for the transformation of data in order to conceal its information content, or prevent its undetected modification, or prevent its unauthorized use (or any combination of these)
cubicle switchgear metal-enclosed switchgear that does not have separate compartments for the switching device, cable box and busbars
cumulative distribution function (of a sample of customers’ loads): function that gives the probability that the load sample will be less than or equal to a specific value of the load current
cumulative energy quantity of energy (kilowatt-hour, kilovar-hour or kilovolt-ampere hour) over a period of time
current circuit internal connections of the meter and part of the measuring element through which flows the current of the circuit to which the meter is connected [SANS 62052-11]
current circuit circuit of a measuring instrument in which the current is equal or proportional to the current of the circuit to which the measuring instrument is connected
current pick-up setting user settable current level above which the fault path indicator (FPI) will indicate a transgression of the overcurrent pick-up setting
current rating (of cables) r.m.s. value of current that a cable can carry continuously under the specified normal conditions of use and behaviour.
current rating (of cables) rated normal current of a cable is the r.m.s. value of current that the cable can carry continuously under the specified conditions of use and behaviour.
current transformer (CT) instrument transformer in which the secondary current, in normal conditions of use, is substantially proportional to the primary current, and differs in phase by an angle which is approximately zero for an appropriate direction of the connections [IEC]
customer person or legal entity that has entered into an electricity supply agreement with a utility level. The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points.
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customer person or entity that purchases a commodity or service from the supplier
customer party who receives electricity from the supply or distribution undertaking
customer customer or legal entity that has entered into an electricity supply agreement with a utility
customer person (or legal entity) who/that either has entered into a non-grid electricity service agreement with a non-grid service provider, or legally consumes electricity supplied by that non-grid service provider
NOTE A potential customer (i.e. a person or legal entity that applies for or requests a non-grid electricity service within a concession area) is also referred to as a customer.
customer cable connects the customer’s plant to the supply at the metering point
customer categories single load profiles that best describe the customer type, for example, business, industrial, residential, electrification, night time users, agricultural
customer group pools of customers created within the customer base consisting of customers taking supply at the same network position
cut-out see outdoor distribution cut-out, which states: a drop-out vented expulsion fuse-link assembly or solid-link assembly, together with the associated components
cut-out base fixed part of a cut-out, provided with the contacts and terminals
cycle of battery sequence of a discharge followed by a charge or a charge followed by a discharge under specified conditions [IEC]
data information represented in a manner suitable for automatic processing
data information that is contained in electronic format
NOTE Data includes information regarding the quantity of energy used, the revenue due by the customer and the information about the metering installation.
data re-interpretable representation of information in a formalized manner suitable for communication, interpretation, or processing
data acquisition system software package capable of reading the data from all meter types for the transfer to other applications such as the billing system
data concentrator intelligent electronic device (IED) that relays communications from a number of devices to a single device, or vice versa
data concentrator equipment located at each end of a path which enables this path to serve more terminals than there are transmission channels in the common path
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data integrity property that shows that data have not been altered or destroyed in an unauthorized manner
data logger device that is capable of registering meter data such as consumption and demand data referenced to time and date and that has the capability of communicating data to a central point by means of an electronic interface
data point representation in the protocol of an analogue, digital or counter value
data registry information database data structure definition of the elements that comprise a communication packet of information
dead at or near zero potential and disconnected or isolated from any live power system
NOTE Rotating plant should not be regarded as dead until it is not excited and is stationary or being slowly rotated by means of barring gear.
dead adjective describing a studio or other location which has a very short reverberation time, used for example to stimulate open-air acoustic conditions
dead time time between the instant that the current is interrupted by the auto-recloser and the instant the contacts of the auto-recloser close as a result of automatic reclose operation [IEC]
dead time time during automatic reclosing when the power line or phase is not connected to any network voltage
dead time time interval, after the initiation of discharge resulting in a normal pulse, during which a counter tube is insensitive to further ionizing events
deadbreak connector
separable connector that is designed to be connected and disconnected on de-energized circuits only [IEC]
declared voltage voltage declared by the utility as the voltage at the point of supply
NOTE The declared voltage is typically specified in the supply agreement with the customer.
decipherment cryptographic transformation of ciphertext data (see also cryptography) to produce plaintext data; the reversal of encipherment
declared voltage voltage declared by the utility as the voltage at the point of supply levels. The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points
decommission removal of an item of equipment from the network for an extended period (a period exceeding three months)
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dedicated supply where a network or a portion of a network is considered dedicated according to the best judgement at the time
de-energized disconnected from any live system
default group See default supply group
default supply group supply group that associates a set of electricity dispensers which have not yet been allocated to a unique supply group or a common supply group, and in which each and every electricity dispenser in the supply group has a unique dispenser key
definite time lag protection element protection element with a time delay capable of being set that is constant above the pick-up current setting
delayed protection operation protection function that consists of a family of curves with operating times inversely proportional to the fault current as a multiple of the pick-up setting
delayed protection operation protection function that enables delayed breaker operation, be it due to an inverse definite minimum or a definite time lag protection element
demand magnitude of an electricity supply, expressed in kilowatts or kilovolt-amperes
demand average value of power or a related quantity over a specified interval of time
demand integration period interval of time, for example 15 min, 30 min, on which the demand measurement is based [SANS 62051]
demand integration period interval time of (half an hour; quarter of an hour; etc), over which the electricity consumed is integrated in order to determine the average hourly (half-hour; quarter hour) demand
demand meter metering device that indicates or records either the demand, the maximum demand, or both
demand period see demand integration period, which states: The interval of time, for example 15 min, 30 min, on which the demand measurement is based [IEC]
density ratio of the mass to a given volume of oil depth (of voltage dip) difference between the declared voltage and the residual voltage during a voltage dip event. [IEC 61000-2-8, modified]
NOTE 1 The depth may be expressed as a value in volts or as a percentage or per unit value relative to the declared voltage.
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NOTE 2 Frequently the word “depth” is used in a descriptive, non-quantitative sense, to refer to the voltage dimension of a voltage dip, without the intention of specifying whether that dimension is expressed as the residual voltage or depth, as defined above. Care is needed to ensure that this meaning is clear in the context in which it is used.
design tension statutory maximum load (see the Occupational Health and Safety Act, 1993 (Act 85 of 1993), to which the ABC may be subjected
design tension aerial bundled conductor (ABC) statutory maximum load (see the OHS Act), to which the ABC can be subjected
designated person person approved by the purchaser
designated person person who is designated in terms of General Machinery Regulation GMR 2 of the OHS Act, to supervise the use of machinery or electrical apparatus (or both) on or in specific premises
designated person person, officially appointed by the supply authority or by the telecommunication authority, to control a project
designated range range of conductor cross-sectional areas with which the fittings are intended to be used
design-data confidence level level of confidence, expressed as a probability (per unit or percentage), in the accuracy of the data used to estimate the after diversity maximum demand (ADMD) and the slenderness factor for a particular group of customers
NOTE The opposite of design-data confidence level is design-data uncertainty level.
design-data uncertainty level see design-data confidence level, which states: the level of confidence, expressed as a probability (per unit or percentage), in the accuracy of the data used to estimate the after diversity maximum demand (ADMD) and the slenderness factor for a particular group of customers
NOTE The opposite of design-data confidence level is design-data uncertainty level.
developers entities who undertake the required activities of developing a particular area and this could include rezoning land to a different zone and meeting all the requirements set by the Local Government
developing network network, the construction of which has not yet reached the initially planned configuration, and from which temporary or early supply is made available to customers by agreement, in order to avoid delayed service availability
dielectric substance whose basic electromagnetic property is to be polarized by an electric field
dielectric substance that can maintain a steady electric field and hence is an insulator
dielectric test test of short duration which consists of applying a specified voltage to the insulation to prove that it is in accordance with the rated insulation voltage of the circuit, as stated by the manufacturer
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dielectric test
test applied to insulation made by applying a high voltage across the insulation to determine the adequacy of its dielectric strength
dielectric dissipation factor tan delta measurement of the tangent of the phase angle or the tan of the loss angle based on the measurement of the leakage current through the oil, which in turn is a measure of the contamination or deterioration (or both) of oil
dielectric strength ability of oil to withstand electrical stress, and is influenced by the presence of moisture and particulate material in the oil
differential mode (DM) voltage voltage between any two of a specified set of active conductors
differential relay electrical measuring relay the characteristic quantity of which is the result of comparison of the input energizing quantities, either in magnitude or in phase and magnitude [IEC]
differential relay measuring relay having two windings so connected in different parts of a circuit that the relay will operate if the difference between the currents in the two circuits exceeds a specific value
digital representation (of a physical quantity): representation of a physical quantity by discreet numerals of digital signals when the physical quantity to be represented is varied between specified limits
digital signal signal which has a discreet number of ranges and values of the signal parameter, different information being associated with each of the ranges
digital signal discreetly timed signal in which information is represented by a finite number of well defined discrete values that one of its characteristic quantities may take in time
digital signal signal whose information parameter may assume one out of a set of discrete values
direct acting indicating instrument instrument in which the indicating device is mechanically connected to and actuated by the moving element
direct-buried underground cable cable designed to be installed under the surface of the earth, in direct contact with the soil
direct current system; d.c. system electrical system fed by unidirectional voltage [IEC]
direction (of power) direction of power which is considered to be the direction of the corresponding energy transfer
direction (of reactive power) direction of reactive power where a capacitor produces it and an inductor absorbs it
direction of lay lateral direction of inclination to the axis (either left or right hand) of the receding helix formed by a wire or a core in a cable
35 NRS 000-1:2008
direction of lay direction of twist of a layer of wires of a stranded conductor as viewed from the end
direction of lay direction of rotation of a component of a cable in relation to the longitudinal axis of the cable
disc reset time time required for the disc of an electromechanical inverse definite minimum time lag (IDMTL) protection relay to turn back to its original position after it has turned to the position where a protection operation was initiated
discharge controlled removal of electric charge, and thereafter the verification of the absence of charge
discharge (electrical) discontinuous movement of electrical charges through an insulating medium, initiated by electron avalanches and supplemented by secondary processes
discharge current of an arrester impulse current, which flows through the arrester [IEC]
discharge of battery operation during which a battery delivers current to an external circuit by the conversion of chemical energy into electric energy [IEC]
discharge voltage see residual voltage, which states: The voltage that is maintained between the arrester terminals during the passage of discharge current, and that determines the protective characteristics of the arrester
disconnector mechanical switching device that provides, in the open position, an isolating distance in accordance with specified requirements [IEC]
NOTE 1 A disconnector is capable of opening and closing a circuit either when negligible current is broken or made, or when no significant change in the voltage across the terminals of each of the poles of the disconnector occurs. It is also capable of carrying current under normal circuit conditions and carrying, for a specified time, currents under abnormal conditions such as those of short-circuit.
NOTE 2 “Negligible current” implies currents such as capacitance currents of bushings, busbars, connections and very short lengths of cable, currents of permanently connected grading impedances of circuit-breakers and currents of voltage transformers and dividers. For rated voltages of 420 kV and below, a current not exceeding 0,5 A is deemed to be a negligible current for the purpose of this definition; for rated voltages exceeding 420 kV, the manufacturer should be consulted.
NOTE 3 “No significant change in voltage” refers to such applications as the by-passing of induction voltage regulators or circuit-breakers. [IEC]
disconnector device on a surge arrester that will separate the earth tail connection from the arrester when the power-frequency current flowing through the arrester exceeds a specific value
discrimination (in protection) ability of protection devices to disconnect only that section of a power system in which a fault has occurred
discrimination (in telecontrol) minimum time by which events must be separated such that the sequence of their occurrence is determined correctly
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dismantling costs total cost of taking down a network and removing the equipment
dispenser key key associated with an electricity dispenser and used together with the standard transfer algorithm to encrypt tokens generated at a credit dispenser and to decrypt tokens input at an electricity dispenser
distortion undesired change of waveform
NOTE Distortion may result from:
a) non-linear relationship between input and output;
b) non-uniform transmission at different frequencies; and
c) phase shift not proportional to frequency.
distortion (of waveform) change in the form of the ideal waveform, usually by the addition of harmonics
distortion factor ratio of the r.m.s. value of the harmonic content (obtained by subtracting from a non-sinusoidal alternating quantity and its fundamental term) to the r.m.s. value of the non-sinusoidal quantity
NOTE The distortion factor is usually expressed as a percentage. [IEC]
distribution kiosk enclosure, consisting of rear (feeder) compartment and a front (service connection) compartment, used to provide a convenient and safe point from which to distribute electricity to customers.
NOTE The feeder compartment is equipped with phase and neutral busbars, onto which the feeder cables are terminated. The front compartment is equipped with one circuit-breaker or one fuse and its holder, for each customer's service cable. Access to the enclosure may be via the removable cover or hinged access doors. The service connection compartment contains no exposed live parts, and there is no access through to the feeder compartment from the service connection compartment.
distribution fuse cut-out drop-out fuse comprising a fuse-base, a fuse-carrier lined with arc-quenching material, and a fuse-link having a flexible tail, and a small diameter arc-quenching tube surrounding the fuse-element [IEC]
distribution line see distributor, which states: a main low-voltage line or a main telecommunication line
distribution line line which is used for the distribution of electricity
distribution network/system apparatus installed for the distribution of electrical energy
distribution network; distribution apparatus installed for the distribution of electric energy
distribution of electricity transfer of electricity to consumers within an area of consumption [IEC]
distribution transformer voltage step-down transformer to supply a section of a distribution network with electrical energy
distribution undertaking organization that supplies electricity to a group of consumers by means of a distribution system [IEC]
NOTE The preferred term is “electricity supplier”.
37 NRS 000-1:2008
distributor; distribution line that part of a supplier's distribution system to which service cables or conductors are connected for the purpose of supplying electricity to consumers
distributor entity which provides a physical supply (of electricity) to a customer on behalf of a supplier and that is contracted to do so through a connection agreement with that customer [IEC]
distributor overhead line or cable or an underground cable from which service connections are tapped
distributor; distribution line main low-voltage line or a main telecommunication line
disturbance recorder; perturbograph instrument in continuous operation, provided with a memory making it possible to record events and transient variables before and during fault conditions [IEC]
diversity lack of coincidence in the time of consumer’s individual maximum demand. (see maximum demand which states: The highest registered electrical demand that is integrated for a specific period)
diversity factor ratio of the sum of the non-coincident maximum demands of two or more loads to their coincident maximum demand for the same period. The further away from the individual supply points the higher the diversity
diversity factor (DF) sum of the non-simultaneous maximum demands of a number of loads divided by the simultaneous maximum demand
1 = DF(1) and 1 demand ussimultaneo
demands ussimultaneo non of sum = DF(N) ≥
NOTE The DF is always greater than 1 except for one customer when it is equal to 1. The figure of 1000 customers is chosen as a reference base since the diversity factor generally does not increase significantly beyond 1000 customers.
diversity (reception) radio reception method in which one resultant signal is obtained from several received signals which convey the same information but for which the radio path or the transmission channel differs by at least one characteristic such as a frequency, polarization, or the position or orientation of antennas
drip dripping that can accumulate and result in a pool of oil
double busbar substation substation in which the lines and transformers are connected via two busbars by means of selectors [IEC]
double circuit two distinct and separate overhead line circuits that are electrically supplied from different sources and that are supported on a common transmission tower, pole or structure
double circuit line line comprising two circuits not necessarily at the same voltage and frequency installed on the same support
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double earthing switches pair of three-phase earthing switches, one fitted on each side of a disconnector
double earthing switches three-phase earthing switch on each side of a disconnector
double insulation insulation which comprises both basic insulation and supplementary insulation [IEC]
double insulation two-stage insulation, the first being between the live conductors and an intermediate frame and the second between the intermediate frame and the body of the vehicle
dressing of poles attachment of hardware and accessories to poles
drop-out fuse-link assembly (cut-out) assembly that comprises all components that form a complete device intended to protect equipment or parts of a reticulation system (or both), in which the fuse-carrier automatically drops into a position that provides an isolating distance after the fuse has operated
NOTE In this specification the term “cut-out” is often used in place of “drop-out fuse-link” assembly.
dry lightning impulse withstand voltage lightning impulse voltage which the insulator withstands dry, under the prescribed conditions of test
dual-phase system (bi-phase system) distribution system, with two live conductors and a neutral, fed from a centre-tapped single-phase transformer winding
duct cable cable designed to be installed under the surface of the earth in a duct that isolates the cable from direct contact with the soil duplicate supply supply to a load by two circuits which are considered to be independent of each other in terms of security of supply [IEC]
dwelling place or structure of residence
dwelling, rural clustered or scattered structures, usually of low density, not served by a well established infrastructure (roads, telecommunication, etc.), the power is usually supplied radially by overhead lines emanating from one distribution station
dwelling, urban formally or informally built structures, usually of high density, served by a well established infrastructure (roads, telecommunication, etc.), the power network is usually supplied by more than one distribution station
earth (ground) conducting mass of the earth whose electrical potential at any point is conventionally taken as zero [IEC]
earth conductor conductor of low impedance which provides an electrical connection between a given point in equipment (an installation or system) and an earth electrode
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earth connection terminal or clamp at earth potential, to which all the equipment earth wires are connected and to which an earth electrode is connected externally
earth continuity conductor (ECC) conductor that comprises a separate (bare or insulated) cable core or tinned hard-drawn copper wires in cable armour
earthed; earthing electrically connected to the general mass of earth as to ensure the efficient transfer of electrical energy
earth electrode part, or group of parts, of the earth termination system which provides direct electrical contact with, and disperses the lightning current to the general mass of earth
earth electrode conductor or group of conductors in intimate contact with and providing an electrical connection to the earth
earth electrode conductive part, which may be embedded in a specific conductive medium, e.g, concrete or coke, in electric contact with the earth
earth electrode one or more conductive parts that are embedded in the earth for the purpose of making effective electrical contact with the general mass of the earth
earth electrode; ground-electrode (USA) conductor or group of conductors in intimate contact with and providing an electrical connection to earth [IEC]
earth fault fault caused by a conductor being connected to earth or by the insulation resistance to earth becoming less than a specified value
earth fault factor at a given location of a three-phase system, and for a given system configuration, the ratio of the highest r.m.s. phase-to-earth power frequency voltage on a healthy phase during a fault to earth affecting one or more phases at any point on the system to the r.m.s. phase-to-earth frequency voltage which would be obtained at the given location in the absence of any such fault [IEC]
earth grid earth electrode consisting of a large rectangular arrangement of conductors buried in trenches and divided by longitudinal and transverse conductors into a number of smaller rectangles having mesh dimensions of the order of five meters or greater earthing lead conductor, including any clamp or terminal, by which connection of the consumer’s earth terminal is made
earthing lead conductor, including any clamp or terminal, by which connection of the consumer’s earth terminal is made
earth leakage current current flowing from the live parts of the installation to earth, in the absence of an insulation fault
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earth leakage current current flowing to earth on account of imperfect insulation
NOTE In the context of this code of practice, the earth leakage current would flow as a result of an insulation failure on the electrical apparatus in the consumer's installation or as a result of the bridging of insulation by any means, for example, a consumer's making inadvertent contact with a live conductor or terminal.
earth leakage protection form of protection in which an earth leakage unit is used
earth leakage unit device that is capable of detecting the flow of a specified or predetermined current from a circuit to earth and of disconnecting automatically and reliably the affected circuit within a specified time when such current exceeds the specified or predetermined value
earthing position (of a withdrawable part) position of a withdrawable part in which the closing of a mechanical switching device causes a main circuit to be short-circuited and earthed
earth resistance resistance of the electrode and surrounding earth as measured between the earthing lead and ground earth resistivity resistance between the opposite faces of a cube of earth having sides of 1 m in length
earth rod earth electrode consisting of a metal rod driven into the ground
earthing system system intended to provide at all times, by means of one or more earth electrodes, a low impedance path for the immediate discharge of electrical energy, without danger, into the ground
earth terminal terminal connected to the accessible metal parts of a machine, intended to be connected to an earth or protective conductor
earth terminal (consumer installation) any clamp or terminal at the point of supply, by means of which the exposed conductive parts of the consumer's installation are connected to an earth electrode or to the supplier's protective conductor
earth terminal terminal intended for connection to the earth
earth terminal terminal fitted on plant or equipment that provides a means of connection for an earth conductor
earth terminal; ground terminal (USA) terminal fitted on equipment and providing a means of connection for an earth conductor [IEC]
earth termination system that part of an external lightning protection system which is intended to conduct and disperse lightning current to the general mass of earth
earthed connected to the general mass of earth in such a manner as to ensure, at all times, an immediate
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safe discharge of electrical energy
NOTE This definition applies only in respect of the supply authority.
earthed connected to the general mass of earth as to ensure an immediate safe discharge of electrical energy
earthed neutral system system in which the neutral is connected to earth, either solidly, or through a resistance or reactance of low enough value to reduce materially transient oscillations and to give a current sufficient for selective earth fault protection
earthed voltage transformer single-phase voltage transformer which is intended to have one end of its primary winding directly earthed, or a three-phase voltage transformer which is intended to have the star point of its primary winding directly earthed
earthed; earthing connected to the general mass of the earth as to ensure an immediate safe discharge of electrical energy
earthing gear; earthing device fixed or portable appliance used for earthing electrical apparatus
earthing label printed form or label attached to an apparatus to indicate that it has been earthed
earthing lead conductor including any clamp or terminal, by which connection of equipment’s earth terminal or conductor to an earth electrode is made earthing position (of a withdrawable part) position of a withdrawable part in which the closing of a mechanical switching device causes a main circuit to be short-circuited and earthed
earthing switch in a substation, a special disconnector which is intended to connect phase conductors to earth for safety purposes [IEC]
earthing switch mechanical switching device for earthing parts of a circuit, capable of with-standing for a specified time currents under abnormal conditions such as those of short-circuit, but not required to carry current under normal conditions of the circuit [IEC]
NOTE 1 An earthing switch can have a short-circuit capacity.
NOTE 2 An earthing switch can be incorporated into a disconnector.
earthing system (rn); grounding system (USA) arrangement of connections and devices necessary to earth equipment or a system separately or jointly [IEC]
earth termination system that part of an external lightning protection system which is intended to conduct and disperse lightning current to the general mass of earth
economical load of a unit load corresponding to the minimum of the curve of the heat rate as a function of the load [IEC]
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effectively earthed system earthed system in which the healthy phase power-frequency phase-to-phase over voltages associated with the earth faults are limited to 80 % of the highest phase-to-phase voltage of the system
efficiency ratio of active output power to active input power, expressed per unit or as a percentage
efficiency ratio of output power to input power of a device
efficiency (of inverter) ratio of the output power at unity power factor to the input power which is the product of the measured d.c. voltage and the measured d.c. current
electric field plot diagram that shows the position of the high-voltage conductors, earth wires and ADSS on the structure together with the lines of electric fields around them electric line arrangement of conductors, insulating materials and accessories for transferring electricity between two points of a system
electrical clearance distance in air which serves as protection against electrical breakdown. In generic terms, the electrical component of the minimum working distance between two electrodes required to prevent spark over under the most severe electrical stress that will arise under the chosen conditions
electrical clearance separation distance between conductors
NOTE This is based on the minimum distance specified in the Occupational Health and Safety Act when allowing for mid-span swing.
electrical clearance (of a contact line) minimum distance permitted between fixed structures and parts energized at contact line voltage
electrical distance distance in air required to prevent with a probability considered as negligible a disruptive discharge between energized parts or between energized parts and earthed parts (or both) during live working
electrical distance DU distance in air that serves as protection against electrical breakdown during live working [IEC 61472] electrical distance distance in air which serves as protection against electrical breakdown during live-line working [IEC]
electrical equipment transformer, capacitor, voltage regulator, recloser, switchgear or cable that contains dielectric fluid
electrical power system/network (in a broad sense) electrical power system; power network: particular installations, substations, lines or cables for the transmission and distribution of electricity [IEC]
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electrical power system; power system electricity supply system (in a broad sense). All installations and plant provided for the purpose of generating, transmitting and distributing electricity [IEC 601-01-01]
electricity dispenser (ED); prepayment meter electricity metering device that can (by means such as tokens, cards, and keypads) be programmed to allow the flow of a prepurchased amount of energy through an electric circuit
NOTE 1 An ED is a metering device that is installed at the customer's premises and allowing the customer to consume the units (kilowatt-hours) of energy for which he/she has purchased credit.
NOTE 2 An ED comprises at least a token registering system, credit memory, a kilowatt-hour meter, a credit memory decrement system and a supply interruption breaker.
NOTE 3 The more generic term "prepayment meter" is the preferred term for an ED.
electricity dispenser (ED) key register physically secure environment for the non-volatile storage of the electricity dispenser's current dispenser key
electricity distribution networks electrical infrastructure of the distributor over which electrical energy is transported from source to point of delivery to customers. This includes all assets including substations with their buildings and ground, lines and cables with servitudes, control equipment, meters and service connections
electricity meter device which measures and registers the integral of an electrical quantity with respect to time
electricity supply industry generation, transmission and distribution of electricity
electricity sales system system that consists of combinations of management information systems/management control systems, system master stations, credit dispensing units and electricity dispensers operated by a distributor or by a number of distributors, for the sale of electricity
NOTE The term “electricity dispensing systems” is used synonymously with the term “electricity sales systems”.
electromagnetic compatibility ability of a device to operate without malfunction in the presence of external electromagnetic interference, as well as the limitation of electromagnetic interference produced by the device itself that could cause malfunction of adjacent equipment such as radios
electromagnetic compatibility electromagnetic compatibility is the condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the same environment
electromagnetic compatibility (EMC) ability of equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment
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electromagnetic disturbance an electromagnetic phenomenon which may degrade the performance of a device, equipment or system. An electromagnetic disturbance may be electromagnetic noise, an unwanted signal or a change in the propagation medium itself
electromagnetic environment the totality of electromagnetic phenomena existing at a given location
electromagnetic interference (EMI) degradation of the performance of equipment, transmission channel or system caused by an electromagnetic disturbance
electromagnetic emission phenomenon by which electromagnetic energy emanates from a source electromechanical meter metering device that measures active or reactive energy consumption electromechanically by means of the Ferraris principle NOTE The product of voltage and current magnetic fields causes a torque proportional to the active or reactive power on a rotating metallic disc. Integration of power is achieved by registering the number of revolutions of the disc through a gear ratio.
electromechanical regulator regulator that uses electromechanical switching devices to control the flow of charge to a battery
NOTE The rate of switching frequency is usually low.
electronic meter meter that converts voltage and current inputs into signals, via VTs, CTs and electronic circuits, and where the consumption is displayed through an LCD display electrostatic discharge transfer of electrostatic charge between bodies of different electrostatic potential, in proximity or through direct contact [IEC]
emergency switching operation intended to remove as quickly as possible danger which may have occurred unexpectedly
emergency switching opening, only, of such breakers or switches as may be necessary to avoid imminent danger to life or damage to apparatus
encipherment cryptographic transformation of plaintext data (see cryptography (3.1.8)) to produce ciphertext data
enhanced performance architecture EPA reduced protocol stack that comprises three layers as defined by IEC 60870-5-3 enclosure any room, chamber, yard or enclosed area in which it is possible for a person from ground or floor level to make inadvertent contact with, or come into close proximity of, live conductors or apparatus
45 NRS 000-1:2008
enclosure weatherproof housing that is custom-made, or a standard ISO container
enclosure part providing protection of equipment against certain external influences and, in any direction, protection against direct contact
enclosure housing affording the type and degree of protection suitable for intended application
encryption See encipherment
end cap device placed on the ends of a cable to prevent the ingress of moisture during storage, transportation and installation
end cap cap that is used to seal the end of an insulated conductor against the ingress of moisture and that is held in position by elastic forces only
energy scalar quantity which characterizes the ability of a physical system to do work, and which is conserved for any transformation of the system
NOTE Energy exists in different forms that are transformable into each other.
energy integral of the active power with respect to time
energy absorption capacity
maximum amount of energy (expressed in kilojoules per kilovolt of rated voltage) that an arrester can absorb without its thermal stability being adversely affected
energy delivered [energy purchased by the utility] energy measured at substation feeder level from which customers are connected;
NOTE The difference between energy delivered and energy sales will give total losses.
enhanced performance architecture reduced protocol stack that consists of three layers, as defined by IEC
equipment electrical equipment such as support structures, pole mounted transformers, miniature substations, service distribution boards, etc
equipment associated assemblies intended to achieve a defined final objective
equipment single apparatus or set of devices or apparatuses, or the set of main devices of an installation , or all devices necessary to perform a specific task
46 NRS 000-1:2008
equipment port (see NOTE 3) particular interface of the equipment which couples this equipment with or is influenced by the external electromagnetic environment
Figure 1 — Examples of equipment ports equipotential platform environment where all metallic structures in the vicinity of electronic equipment (for example, cabinets and cable trays) are bonded together, in order to render more benign the electromagnetic environment within which the electronic equipment operates
NOTE 1 The process of creating an equipotential platform is known as equipotentialization.
NOTE 2 An equipotential platform is typically, but not necessarily, connected to earth.
extra high voltage set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range 220 kV > Un ≤ 400 kV
equipotential platform environment where all metallic structures in the vicinity of electronic equipment (for example, cabinets and cable trays) are bonded together, in order to render more benign the electromagnetic environment within which the electronic equipment operates.
The process of creating an equipotential platform is also known as equipotentialization
NOTE An equipotential platform is typically, but not necessarily, connected to earth.
equivalent area cross-sectional area of a conductive material required to provide the same conductive properties as the conductor used as a reference
NOTE This term is used to accommodate the possible use of different materials in, for example, phase and neutral conductors.
equivalent span fictitious single span in which tension variations due to load or temperature changes are nearly the same as in the actual spans in a section of overhead cable [IEC]
ergonomic distance distance in air, taken into account inadvertent movement and errors in judgement of distances while performing work
a.c. power port
d.c. power port
Earth port
Equipment
Enclosure port
Control port
Signal port
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ergonomic distance DE distance that allows for inadvertent movement or errors in appraising distances while performing work [IEC 61472] NOTE This distance takes into consideration the actions of the persons as well as the tools that are used and manipulated.
estimation process whereby values are inserted into the set of energy usage data for a customer and where such data is not available through maloperation of equipment or failure to retrieve it within a specified performance period or when metering is deliberately not reading at every billing interval
European standard (EN) standard adopted by CEN/CENELEC (see 3.2) for implementation in the European Union even harmonics see voltage harmonics
events (occurrences) events that are detectable by the sectionalizer control and that represent the fault conditions against which the power line is to be protected
excess reactive energy total reactive energy in excess of a certain percentage of the total active energy
NOTE This term is directly related to the implementation of Eskom T2 time-of-use tariff option (Megaflex).
Exexclusive-or addition: See modulo-2 addition (3.1.27). (NRS 009-7:1999)
experienced person see the OHS Act, 1993 (Act 85 of 1993)
explosion vent normally closed opening, preferably arranged at the rear or bottom of the metallic enclosure, which, in the case of an internal electrical fault, will rupture or open to release overpressure in a controlled manner to the atmosphere
exposed conductive part any conductive part that can be touched and is not live but can become live under fault conditions
expulsion fuse fuse in which operation is accomplished by the expulsion of gases produced by the arc [IEC]
external development services networks that fall outside the boundaries of a particular development and are required for a particular development
external lightning protection system group of measures that are applied to the outside of a structure, and that involve so-called lightning conductors (air terminations), earthing conductors (down conductors) and earth points (earth terminations) , in order to limit the damaging effects of lightning to the structure and to provide a pre-determined path for lightning discharge
external supply term that generally refers to the bulk electricity supply to a township
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extra high voltage set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range 220 kV less than Un or equal to or less than 400 kV. The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points
extra high voltage networks networks at voltages above 132 kV. This includes all Eskom’s transmission assets even where at different voltages as defined in the Transmission Grid Code
extra high voltage to HV transformation networks transformation networks between EHV and HV voltages
extruded insulation insulation that consists generally of one layer of a thermoplastic or thermo-setting material and that is applied by an extrusion process [IEC]
factor of safety (of any component) ratio of a component’s failing load to the maximum working load for which it is designed
failing load load at which a deflection begins to show a disproportionate increase in relation to an increase in load
fast curve protection function family of near-inverse curves with approximately equal operating (delay) times relative to the multiple of the pick-up setting
fast protection function family of near-inverse curves with approximately equal operating (delay) times relative to a multiple of the pick-up setting
fault unplanned occurrence or defect in an item which can result in one or more failures of the item or of other associated equipment [IEC]
fault (electric power system) unplanned occurrence or defect in an item which may result in one or more failures of the item itself or of other associated equipment
fault current (in a network) current flowing at a given point of a network resulting from a fault at another point of this network
fault current (insulation) current that results from an insulation failure or from the bridging of insulation
fault locator device used for fault location [IEC]
fault path indicator pole-mounted electronic device, specifically designed for the detection of phase and earth faults on overhead distribution lines
feeder electric line originating at a main substation and supplying one or more secondary substations [IEC]
feeder untapped overhead or underground three phase cable, or set of conductors connecting distribution stations
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feeder bay in a substation, the bay relating to a feeder or a link to a transformer, a generator or another substation [IEC]
feeder circuit-breaker in a substation, a circuit-breaker which is located within a feeder bay and through which a feeder can be energized [IEC]
feeder compartment that part of a meter kiosk where the feeder cables are terminated onto busbars
feeder disconnector disconnector which is located in series at the end of a feeder, within a substation bay, in order to isolate the feeder from the system [IEC]
feeder (feed line) a radio frequency transmission line interconnecting an antenna and a transmitter or receiver. For an antenna comprising more that one driven element, a radio frequency transmission line interconnecting the antenna input and a driven element.
feeder (feeder cable) electrical connection between the contact line and a substation
ferrule (cable) accessory in the form of a short tube to provide cable support or termination of a cable screen
ferrule (optical fibre) mechanical fixture, generally a rigid tube, used to confine the stripped end of a fibre bundle or an optical fibre
ferrule; through connector connector for connecting two consecutive lengths of conductor
fill factor way of summarizing the differences in the shapes of photovoltaic module current-voltage curves. It is defined as Vmax multiplied by Imax divided by Voc multiplied by Isc where Vmax is the module voltage at maximum power, Imax. is the module current at maximum power, Voc is the module voltage on open circuit, Isc is the module current on short circuit. All quantities at standard test conditions (see standard test conditions)
NOTE The fill factor is sometimes used as an indicator of the quality of the photovoltaic cells and modules. In high quality modules, the fill factor is higher. The typical fill factor of a high quality module should exceed 75 %.
filler inert material in a disk compound which is used as an extender in the plastic material
filler material used to fill the interstices between the cores of a multiconductor cable
filter component that is designed specifically for its frequency domain response and that is intended to attenuate unwanted interference or noise
NOTE A filter alone is usually a surge protective device.
filter material placed in a beam of radiation in order to produce filtration
filter linear two-port device designed to transmit spectral components of the input quantity according to a specified law, generally in order to pass the components in certain frequency bands and to attenuate those in other bands
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filter (optical) regularly transmitting device used to modify the radiant or luminous flux, the relative spectral distribution, or both, of the radiation passing through it
NOTE A distinction is made between selective filters and non-selective filters or neutral filters or neutral grey filters according as they do or do not alter the relative spectral distribution of the radiation. A selective filter that makes a significant change in the chromaticity of the radiation is called a coloured filter; one that alters the spectral distribution but, because of metamerism, transmits radiation of nearly the same chromaticity as that of the incident radiation, may be called a grey filter.
final tripping; lock-out
disconnection of faulty equipment or a part of the network after a predetermined number of unsuccessful reclosures [IEC]
firm supply design standard that will ensure single contingency in security of supply. Sometimes referred to as N-1.
fixed wiring switchgear of modular design with each unit comprising a fixed circuit-breaker (non withdrawable), switch or switch fuse combination and, where required, its associated off-load disconnector
fixed wiring wiring that is permanently installed to various outlet points
flagged data measurement time interval in which interruptions, dips or swells occur, the measurement results of all other parameters made during this time interval are flagged [SANS 61000-4-30]
NOTE 1 The “flagging” concept avoids counting a single event more than once in different parameters, for example counting a single dip as both a dip and a frequency variation. Flagging is only triggered by dips, swells and interruptions. The detection of dips and swells is dependent on the threshold selected by the user, and this selection will influence which data are “flagged”. NOTE 2 The flagging of data is applicable during measurement of power frequency, voltage magnitude, flicker, voltage UB, voltage harmonics and interharmonics, mains signalling and measurement of underdeviation and overdeviation parameters.
flange mounting plate connecting the enclosure to the equipment
flange fixed or removable circular disk forming one piece with the hub, on one or both sides of a hub for the purpose of protecting the magnetic tape wound on the hub
flashover breakdown of electrodes in a gas or in a liquid or in a vacuum, at least partly along the surface of solid insulation
flashover short-circuit caused by arcing between brushes or brush-holders at the surface of the commutator of an electrical machine or from any of these parts to the frame
flashover disruptive discharge over a solid surface [IEC]
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flashover (sparkover; disruptive discharge) passage of an arc following dielectric breakdown
NOTE This term is used when a disruptive discharge occurs over the surface of a solid dielectric surrounded by a gaseous or liquid medium.
flash point temperature at which sufficient vapour is given off by the oil to support combustion
float charge voltage voltage at which a battery is maintained in a fully charged condition without excessive gassing
footing resistance resistance of a structure to earth
forced interruption interruption that:
a) occurs when a component is taken out of service immediately, either automatically or as soon as switching operations can be performed, as a direct result of emergency conditions, or
b) is caused by human error or by the improper operation of equipment or human error.
forced interruptions on EHV and HV networks
a) momentary interruptions (EHV/HV)
forced interruptions in the range > 3 s to ≤ 1 min.
b) sustained interruptions (EHV/HV) forced interruptions with a duration greater than 1 min
NOTE 1 In general a one minute limit differentiates all automatic reclose events from events involving operator intervention. A one minute classification is commonly used internationally by transmission utilities.
NOTE 2 In some cases, Transmission utilities may use a ≤ 10 s sub-classification to cover three phase auto-re-closer events not related to generation supply points (the latter may have dead times of 20 s to 30 s and restoration times of up to 45 s).
forced interruptions on MV and LV networks
a) momentary interruptions (MV/LV)
forced interruptions in the range > 3 s to ≤ 5 min
b) momentary interruption events (MV/LV) where an interrupting device has a sequence of operations, for example if a recloser or breaker operates two, three or four times and then holds, those momentary interruptions shall be classified as considered as one momentary interruption event. Such a sequence shall be completed in a specified time not to exceed 5 min
c) sustained interruptions (MV/LV)
forced interruptions with a duration greater than 5 min
forced outage outage due to the unscheduled putting out of service of an item [IEC]
forced outage unplanned outage whose onset, automatic or manual, cannot be deferred
formed tie custom-designed wire strand, or set of wire strands or plastics strands, that has been factory formed to suit a particular insulator neck size, or conductor or stay wire type (or both)
52 NRS 000-1:2008
frequency; power frequency frequency of alternating voltage generated by power system generators
frequency frequency of alternating voltage generated by power system generators. The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points
frequency reciprocal of the period
frequency converter substation substation in which an a.c. current at a given frequency is converted into an a.c. current at another frequency [IEC]
fully insulated enclosure unfilled enclosure where those parts of the bushings inside the enclosure, including all live metal parts and cable cores, are fully insulated for the appropriate insulation level
functionality defined capability to perform certain functions
furanic content content normally produced by the solid insulation in power equipment due to ageing and fault conditions in the equipment, and is a by-product of paper degradation fuse carrier movable part of a fuse designed to carry a fuse-link
fuse element part of the fuse-link that is designed to melt under the action of a current that exceeds some definite value for a definite period of time [IEC]
fuse switch switch (disconnector) in which a fuse-link or a fuse-carrier whose fuse-link forms the moving contact
fuse-carrier movable part of a fuse-link assembly designed to carry a fuse-link [IEC]
fuse-link part of a fuse, including the fuse element(s), intended to be replaced after the fuse has operated [IEC]
galvanic corrosion enhanced corrosion of a metal owing to its being in electrical contact with a conductor of a more noble metal in an electrolyte
gapless arrester arrester that has no integrated series or parallel spark gaps
gapless metal-oxide surge arrester arrester having non-linear metal-oxide resistors connected in series and/or in parallel without any integrated series or parallel spark gaps [IEC]
gas-insulated line electric line whose conductors are contained in an enclosure and insulated with a compressed gas [IEC]
53 NRS 000-1:2008
gas-insulated switchgear switchgear which is totally enclosed and whose conductors and busbars are insulated by an inert gas such as sulphur hexafluoride (SF6)
gassing tendency property, which is a function of the capacity of the oil, dependent on the structure of the oil, to absorb the hydrogen formed by electrical discharges
NOTE Two types of oil are available – gas evolving and gas absorbing oils.
gas turbine set thermal generating set in which the prime mover consists of a gas turbine
general purpose switch switch capable of performing, with currents up to its rated breaking currents, all making and breaking operations which may normally occur in distribution systems as well as carrying and making short-circuit currents [IEC]
general symbol symbol, usually simple, common to a whole family of items, and characteristic of that family
generating set group of rotating machines transforming mechanical or thermal energy into electricity [IEC]
generating station building that contains the necessary equipment for generating electrical energy
generation of electricity process whereby electrical energy is obtained from some or other form of energy
generation schedule scheduling of generation facilities for a specified period [IEC]
generation system total means of generation in a system [IEC] One can also consider only one given subgroup (thermal generation system for example)
generator authorized entity that is responsible for producing electricity and making it available to the power system
generator electrical portion of generating plant; its circuit shall include all apparatus between its outgoing terminals and the busbar isolators and between its neutral terminals and earth
generator machine which converts mechanical energy into chemical energy
ghosting false reflection which appears at an integral multiple of the distance from the initial (true) reflective event
NOTE For example if a large reflection occurs at say 1 000 m, there could be a ghost at 2 000 m due to the reflective light bouncing back and forth within the fibre.
graphical symbol figure, mark or character conventionally used on a diagram or other document to represent an item or a concept
grid current magnitude of the current injected into the soil by the earthing system. In the extreme the grid current equals the fault level
54 NRS 000-1:2008
grid resistance earth resistance of the earth grid
ground general mass of the earth (terra firma)
ground clearance minimum distance between the specified conductor(s) and the ground ground clearance minimum distance between the conductor and ground level in a span with the conductor at its maximum design temperature, usually 50 ºC
ground span horizontal distance between supporting structures that, on level ground with the conductor at maximum sag, enables the statutory clearance of the conductor above the ground to be achieved
NOTE The ground span is dependent on the structure height, the type of conductor, the temperature, and the tension limits within which the conductor is designed to operate.
guy grip dead-end fitting preformed fitting for attaching a stay wire or rope to other stay components such as anchor rods, thimbles and stay insulators
half-hour period that ends on each hour and half-hour
hard disconnection service is removed completely (i.e. the asset is removed from the field)
harmonics sinusoidal components of the fundamental current or voltage waveform (i.e. 50 Hz) that have frequencies that are integral multiples of the fundamental frequency. (see also voltage harmonics) harmonics components of the output voltage or output current waveform that have frequencies different from that of the standard frequency (50 Hz in South Africa)
NOTE Harmonics exist if the waveforms are not exactly sinusoidal.
harmonization (of national standards) prevention or elimination of differences in the technical content of standards having the same scope, particularly those differences that may cause hindrances to trade
harmonized European standard (in the sense of the EMC-Directive) European standard published in the Official Journal of the European Communities (OJEC) supporting the presumption of conformity with the protection requirements of the EMC Directive high current impulse of an arrester peak value of discharge current having a 4/10 microsiemens impulse shape which is used to test the stability of the arrester on direct lightning strokes [IEC]
high frequency (HF) (see NOTE 2) frequency above 9 kHz
55 NRS 000-1:2008
high voltage
1) In a general sense, the set of voltage levels in excess of low-voltage.
2) In a restrictive sense, the set of upper voltage levels used in power systems for bulk transmission of electricity.
high voltage set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range 44 kV less than Un or equal to or less than 220 kV
high voltage networks lines, cables, switches, protection and associated equipment at voltages from 44 kV to 132 kV
high voltage (HV) (networks) set of nominal network voltage levels that are used in power systems for bulk transmission of
electricity in the range 33kV < Un ≤ 220 kV [SANS 1019, modified]
high voltage to medium voltage transformation networks transformation networks between HV and MV voltages. This includes all substation equipment
high voltage 1 (high tension) voltage having a value above a conventionally adopted limit
high voltage 2 (high tension) highest of two or more voltages in an apparatus or installation
highest (lowest) voltage of a system highest (lowest) value of operating voltage which occurs under normal operating conditions at any time and any point in the system [IEC]
NOTE Transient over voltages caused, for example, by switching operations and abnormal temporary variations of voltage are not taken into account.
highest system voltage highest r.m.s. phase-to-phase voltage of the system
highest voltage for equipment (Um) highest r.m.s. phase-to-phase voltage for which the equipment is designed in respect of its insulation as well as other characteristics which relate to this voltage in the relevant equipment standards [IEC]
highest voltage for equipment (Um) (transformer winding) applicable to a transformer or reactor winding. The highest r.m.s. phase-to-phase voltage for which a transformer or reactor winding is designed in respect of its insulation
NOTE Um is the maximum value of the highest voltage of a system to which the winding may be connected, in respect of its insulation.
high-reactance current transformer transformer in which the effects of leakage flux are such as to prevent an assessment of its performance being made from a knowledge of the exciting current, secondary winding resistance and turns ratio
high-voltage d.c. link; HVDC link installation for transmitting large quantities of electricity at high-voltage d.c. including the converter substations [IEC]
NOTE In this context, high voltage includes medium, extra-high and ultra-high voltages. [non-IEC note]
high-voltage yard; HV yard enclosure that contains exposed overhead medium voltage, high-voltage; extra-high voltage or ultra-high voltage components
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horizontal personal reach horizontal distance from position of feet (when together) to the tip of the outstretched horizontal hand hot stand-by all the means of generation ready to start-up for prompt coupling to the system [IEC]
hot start-up of a thermal generating set process by which the generating set is raised to speed, the machine connected to the system and loaded after a short period of being out of operation which did not change the turbine thermal state very much [IEC]
housing external insulating part of the insulator that also provides the necessary creepage distance
housing part of a kiosk that encloses the internal parts and components hydroelectric installation ordered arrangement of civil engineering structures, machinery and plant designed chiefly to convert the gravitational potential energy of water into electricity [IEC]
hydroelectric power station power station in which the gravitational energy of water is converted into electricity [IEC]
IDMT relay relay, the minimum operating time of which is adjustable and is inversely proportional to the fault current
immunity (to a disturbance) ability of a device, equipment or system to perform without degradation in the presence of an electromagnetic disturbance impedance earth neutral system system in which at least one neutral point is earthed through a device having an impedance designed to limit the line-to-earth short-circuit current
impedance earthed (neutral) system system whose neutral point(s) is (are) earthed through impedances to limit earth fault currents [IEC]
impulse time integral of a force over the time during which the force is applied
impulse pulse that, for a given application, approximates a unit pulse or a Dirac function
impulse intentionally applied periodic transient voltage or current, which usually rises rapidly to a peak and then falls more slowly to zero
NOTE Such an impulse is in general well represented by the sum of two exponentials.
impulse voltage test test that consists of applying a specified impulse voltage to the insulation to prove the ability of a device to withstand without damage, over voltages of very high value and very short duration
in commission state of any apparatus in the normal operating mode, or available for immediate use. The state of an item of being able to perform its required function [IEC]
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incident event of external or internal origin, affecting equipment or the supply system and which disturbs its normal operation [IEC]
independent manual operation stored energy operation where the energy originates from manual power stored and is released in one continuous operation, such that the speed and force are independent of the action of the operator [IEC]
independent test facility organization that is not connected to, or part of, the supplier and that is accredited, to the satisfaction of the purchaser, to carry out the required tests
indoor substation substation sheltered from external weather conditions by being installed within a building [IEC]
indoor termination termination that is intended for use where it is not exposed to either solar radiation or weathering
induction meter see electricity meter, which states: a device which measures and registers the integral of an electrical quantity with respect to time
induction meter energy meter which operates by the rotation of the disc of an induction measuring element
informative elements elements that are included in a document for information or guidance only and that are not considered to be part of the requirements of the document
infrastructure permanent structural installations that form the structural foundation for the telecommunication authority (TA) or the supply authority (SA) to continue its operation and business
NOTE Typical examples of equipment that form part of such installations would be poles, cables and conductor(s).
infrastructure developments activities where the nature of an area is transformed through the installation of infrastructure
inhibited or uninhibited, adj condition of oil where organic compounds (anti-oxidant additives) are found in an insulating oil that undergoes oxidation
NOTE During the oxidation process, chemically unstable intermediate compounds are formed, with the production of final oxidation products such as organic acids and sludges. A product that can render this oxidation reaction inactive would be an inhibitor. Oils do contain a certain portion of natural inhibitors, but additional inhibitors may be added to oil. The most commonly used inhibitor is Diisobutyl-para-cresol (DBPC), also known as Butylated hydroxytoluene (BHT).
initialized module secure module loaded with master keys, registered at the Eskom key management centre
NOTE An initialized module has been loaded with master keys but not with vending keys.
input impedance impedance presented by a piezoelectric filter to the signal source when terminated in the specific load impedance
input impedance input electrode impedance
58 NRS 000-1:2008
input impedance impedance of a network seen as the terminals of an input port, when all other ports are connected to a specified terminating immittances
input impedance impedance of the input circuit that is measured between the input terminals of the apparatus under operating conditions [IEC]
input-output voltage dependency percentage change in output voltage when the input voltage is varied over a specified range
inrush restraint built-in filter that filters out all 2nd and 3rd harmonics from the measured current during inrush and cold load pick-up conditions
in-situ testing testing done under live conditions in a non-intrusive way to verify the accuracy of a metering installation
inspection visual or audible (or both) examinations that can be assisted by mechanical or electrical (or both) means, that will detect obvious unsatisfactory conditions or discrepancies (IEC modified)
installed system-minutes unit used to approximate a measure of the relative loss of supply in an electricity supply network
installing authority authority that initially erects and owns a structure
instantaneous protection element element with no intentional time delay active above a pre-determined pick-up current setting
instrument transformer specially designed to maintain a certain relationship in phase and magnitude between the primary and secondary voltages or currents
instrument security factor (FS) ratio of a rated instrument limit primary current to the rated primary current [IEC]
instrument transformer transformer intended to transmit an information signal to measuring instruments, meters and protective or control devices
instrument transformer current transformer (CT) or voltage transformer (VT) that is used to reduce the value of currents or voltages, respectively, applied to a meter in known and definite ratios that bring the current and voltage to within the range of the meter having normal current and voltage ratings
instrument transformer transformer specially designed to maintain a certain relationship in phase and magnitude between the primary and secondary voltages or currents
instrument transformer accuracy class see accuracy class, which states: A designation that is assigned to an instrument transformer, the current or voltage error and phase displacement which remains within specified limits under prescribed conditions of use [IEC]
instrument transformer accuracy rating (for metering): accuracy class together with a standard burden for which the accuracy class applies
59 NRS 000-1:2008
insulated covered with insulating material of such thickness and properties that the material will prevent the flow of electrical energy between the object so covered and its surroundings or any external object in contact with it [OHS Act]
insulated cable assembly consisting of : a) one or more cores;
b) their individual covering(s) (if any);
c) assembly protection (if any); and
d) protective covering(s) (if any).
additional uninsulated conductor(s) may be included in the cable
insulated tool tool made of conductive material and fully or partly covered by insulating material [IEC]
insulating oil mineral oil used in transformers and other electrical equipment for insulation and cooling insulating pole (working pole) insulating tool made of insulating tube or rod with end fittings [IEC]
insulating tool tool essentially made of insulating material [IEC]
insulation (1) all materials and parts used to insulate conductive elements of a device
insulation (2) set of properties which characterize the ability of an insulation to provide its function
NOTE Examples of relevant properties are: resistance, breakdown voltage.
insulation (of a cable) insulating materials incorporated in a cable, with the specific function of withstanding voltage [IEC]
insulation co-ordination selection of the dielectric strength of equipment in relation to the voltages that can appear on the system for which the equipment is intended and taking into account the service environment and the characteristics of the available protection devices [IEC]
insulation level for a particular item of equipment a characteristic defined by one or two values indicating the insulation withstand voltages
insulation level combination of the following:
a) the rated short duration power-frequency withstand voltage; and
b) the rated lightning impulse withstand voltage.
insulation piercing connector
insulated device that is used for connecting two or more insulated conductors by piercing the insulation of the conductors
insulation piercing connector connector in which electrical contact with the conductor is made by metallic protrusions which pierce the insulation of the cable core
60 NRS 000-1:2008
insulator device that provides both electrical insulation and mechanical linkage between a live conductor and an earthed structure [IEC]
insulator device designed to support and insulate a conductive element
insulator that component of a cut-out base, which is intended to insulate the load-side and the source-side from each other and from earth and which is fitted with an insulator-fixing stem
insulator device intended for electrical insulation and mechanical fixing of equipment or conductors which are subject to potential differences [IEC]
insulator-fixing stem component for attaching an insulator to a mounting L-bracket
integrated control device with built in telecontrol with remote terminal unit (RTU) capabilities
integrating instrument instrument that records the time integral of the measured quantity
integrating period see demand integration period, which states: interval of time, for example 15 min, 30 min, on which the demand measurement is based [IEC]
integrating (measuring) instrument measuring instrument which gives the integral of an input quantity with respect to another quantity, generally time
intelligent electronic device processor-based electronic interface with switchgear that provides protection or system control and data acquisition (SCADA) capability (or both)
interconnected system systems connected together by means of one or more interconnection links
NOTE This term is also used in the singular for a system whose elements are interconnected.
interconnected systems systems connected together by means of one or more interconnection links [IEC]
NOTE This term is also used in the singular for a system whose elements are interconnected
interconnection connection of distinct electric circuits or networks to each other
interconnection (of power systems) single or multiple transmission link between transmission systems enabling electricity to be exchanged between these systems by means of circuits or transformers (or both) [IEC]
interconnection (of power systems) connection of distinct electric circuits or electric networks to each other
interdac 1 connection cable comprising two conductors suitable for single-phase reticulation and connections, and specially developed for intermediate voltage use at 1,9 kV
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interdac 3 three-phase cable with special armouring used as the neutral conductor, specially developed for intermediate voltage use at 3,3 kV
interfacial tension (IFT) measure of the dipole concentration of a liquid
NOTE 1 A test is carried out to measure the strength of the interface between water and oil, which is dependent on the polar groups in the oil.
NOTE 2 The test mentioned in note 1 is a very sensitive test; it will give an indication of the presence of contaminants such as oxidation products or other foreign substances likely to be found.
interharmonics see voltage harmonics
interlock electrical, mechanical or electromechanical device to ensure that operations are performed in a pre-determined sequence
intermediate voltage (IV) a.c. medium voltage in the range 1000 V to 3300 V phase to phase
intermediate voltage distribution distribution system operating at a nominal a.c. voltage of 1,9 kV phase-to-neutral, or 3,3 kV phase-to-phase
intermittent fault fault of an item which persists for a limited time duration following which the item recovers the ability to perform a required function without being subjected to any action of corrective maintenance
intermittent fault transient fault which recurs repeatedly in the same place and due to the same cause [IEC]
internal development services networks that fall within the boundaries of the development and are specifically required to take the required capacity to each stand of the potential customers in the development
internal lightning protection system group of measures that are applied to the volume inside a building, to render the electromagnetic environment more benign
NOTE This usually involves the creation of equipotential platforms and lightning protection zones.
internal network term that generally refers to all electrical distribution equipment within the boundary of a township up to an agreed interface with the external supply
interoperability ability to exchange keys, whether manually or automatically, between equipment supplied by one manufacturer and operated by one party and equipment supplied by another manufacturer and operated by another party
interruptible load load of particular consumers which, according to contract, can be disconnected by the supply undertaking for a limited period of time
interruption phenomenon that occurs when one or more phases of a supply to a customer/group of customers is/are disconnected for a period exceeding 3 s
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interruption (interrupt) suspension of a process, such as the execution of a computer program, caused by an event external to that process and performed in such a way that the process can be resumed
interruption of supply loss of supply to one or several consumers [IEC]
interruption, forced interruption that occurs when a component is taken out of service immediately, either automatically or as soon as switching operations can be performed, as a direct result of emergency conditions, or an interruption that is caused by improper operation of equipment or human error [NRS 047]
interruption, planned interruption that occurs when a component is deliberately taken out of service (by the utility or its agent) at a selected time, usually for the purposes of construction, preventative maintenance or repair
intrinsic error error of a measuring instrument when used under reference conditions
inverse definite minimum time lag protection element protection element, the minimum operating time of which is adjustable and that is inversely proportional to the fault current
inverse definite minimum time relay relay the minimum operating time of which is adjustable and that is inversely proportional to the fault current
inverter device which changes d.c. input into a.c. output [IEC]
inverter static converter for the conversion of direct current to alternating current
inverter electric energy converter that changes direct electric current to single-phase or polyphase alternating currents
inverter a.c/d.c converter for inversion
to disconnect the supply or apparatus (or both) from all possible sources of electrical potential. This may be achieved by opening isolator links, disconnecters or fuses, or by racking-out associated switching devices, or by removing jumper connections
irrecoverable costs labour, transport, contract costs of installing a network and portion of material costs that cannot be re-used when a network is removed island network network that is operated without connection to the main grid
isolate to disconnect from all possible sources of electrical potential
NOTE In this context apparatus may be isolated by the a) opening or removing (or both) of fuses;
b) opening of isolators;
c) removing of jumpers;
d) opening of air-break switches;
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e) withdrawal of truck type switchgear;
f) immobilization of circuit-breakers that have visible contact separation and that are not fitted with grading capacitors; and
g) utilization of an approved change-over circuit-breaker or isolator.
isolate(1)
disconnect completely a device or an electric circuit from other devices or electric circuits
isolate(2) provide, by separation, a specified degree of protection from any live electric circuit
isolated neutral system system that has no intentional connection to earth except through indicating, measuring or protective devices of very high impedance
isolated neutral system system where the neutral point is not intentionally connected to earth, except for high impedance connections for protection or measurement purposes [IEC]
isolation of a unit emergency measure consisting of the disconnection of a unit to maintain the supply of its own auxiliaries [IEC]
isolation voltage maximum a.c. or d.c. voltage that may be continuously applied between the input and either the output or the chassis of equipment
isolator device provided for the purpose of isolating apparatus from the source of electrical energy
isolator apparatus that is provided for the purpose of isolating the supply or apparatus from the source of electrical energy
isolator (deprecated) mechanical switching device which provides, in the open position, an isolating distance in accordance with specific requirements
NOTE A disconnector is capable of opening and closing a circuit only when negligible current is broken or made.
isolator; one-way attenuator two-port device having much greater attenuation in one direction of propagation than in the opposite direction
NOTE An isolator is often used to prevent return reflections along a transmission path.
item any part, component, device, subsystem, functional unit, equipment or system that can be individually considered (IEC) joggle chamber purpose designed panel used to align the busbars of different types of metal-clad switchgear
joint assembly designed to permit connections between two or more optical fibres
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joint device for joining two conductors together, that might or might not be subject to mechanical tension
joint connection between two conductors, sheaths or armour wires including their insulation, if any, to form a continuous circuit
keys keys used to operate safety locks, which are kept in a key safe, and are required for the issue of a work permit
key activation date attribute associated with a vending key value that defines the date upon which the vending key becomes the supply group's current vending key, and the date upon which the associated key revision number becomes the supply group’s key revision number
key block in the context of the standard on data encryption (ANSI X3.92), the 64 bit block of data that contains the 56 bit key
key expiry number attribute associated with a key value that defines the period during which the key value can be used
NOTE 1 A token that is encrypted with a key whose token identifier exceeds the electricity dispenser's key expiry number for the key will be rejected by the electricity dispenser.
NOTE 2 Implementation of key expiry is optional for an electricity dispenser.
key revision number attribute associated with a key value and that provides a key sequencing identifier
key type attribute associated with a key value and that defines the purpose for which the key value can be used
kiosk substation compact substation, often prefabricated and used for distribution purposes [IEC]
kneepoint voltage r.m.s. value of sinusoidal voltage at rated frequency applied to the secondary terminals of the transformer, all other windings being open-circuited, which, when increased by 10 %, causes the r.m.s. value of the excitation current to increase by 50 % [IEC] kVA (demand)
22
22
kvar kWkvarh kWhkVAh
+=+
=TT
where T is the integration period in hours.
kVAh
22 kvarh kWh +
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kvar (demand)
T
kvarh
where T is the integration period in hours.
kW (demand)
T
kWh
where
T is the integration period in hours.
lagging wooden battens fixed to the edges of the cable drum flanges to protect the cable wound on the drum lapped separator (of a cable) separator that consists of tapes applied helically in a concentric layer
large customer large power user with a notified maximum demand that exceeds 100 kVA
large/small customer categories of customers based on the capacity required by a customer
lashed cable telecommunication cable, of circular cross-section, that is attached to a suspender wire on an overhead line, by means of a lashing wire wrapped around the cable and suspender wire
lashing wire thin galvanized or stainless steel wire that is used to attach a telecommunication cable to a suspender wire
lead wires (of a photoelectric control unit three separate wires that lead from a one-part photoelectric control unit and that are intended for direct connection to the power supply and the load
leak continuous dripping that will result in pooling of oil
NOTE Leaking requires corrective action since the electrical equipment will have to be topped-up.
leapfrog developments developments that are remote from the existing available electricity networks of the utility and beyond any short-term expansions of the services
length complete length of cable drawn from a pre-form during manufacturing
length of lay (of a cable) axial length of one complete turn of the helix formed by one cable component [IEC]
licensee see utility (licensee), which states: a body, licensed by the National Electricity Regulator, that generates, transmits or distributes electricity. NOTE Such a body might be the direct licensee, or an agent (sub-distributor) of the licensee.
licensee supply authority licensed by the NER to distribute electricity
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licensee recipient of a licence issued by the NER that authorizes the generation and/or transmission and/or distribution and/or supply of electrical energy
NOTE This licence is renewed on a periodic basis.
life cycle cost net present value of the sum of all the direct and indirect costs incurred to acquire, install, commission, operate, maintain, decommission and dispose an item throughout its life
NOTE The maintenance component of the life cycle cost should include the costs of risk, spares, labour, maintenance facilities and equipment, transport, site establishment and any special training.
life cycle items primary items and all other network items which together account for 80 % of the sum of all life cycle costs lightning arrester device designed to protect electrical apparatus from high transit voltage and to limit the duration and amplitude of the follow current
NOTE They are usually connected between the electrical conductors of a system and earth.
lightning (or switching) impulse (protective level) maximum permissible peak voltage value on the terminals of a protective device subjected to lightning (or switching) impulses under specific conditions [IEC]
lightning impulse impulse that has a front duration of less than a few tenths of a microsecond to less than one microsecond (µs)
lightning impulse voltage impulse of a specified shape applied during dielectric tests with a virtual front duration of the order of 1 µs and a time to half value of the order of 50 µs
NOTE The lightning impulse is defined by the two figures giving these durations in microseconds;
in particular the standard lightning impulse is: 1,2/50 µs
lightning impulse impulse voltage, applied during dielectric tests complying with standards, with a front duration of the order of 1 s and a time to half value of the order of 50 s. give these durations in µs; in particular the standard lightning impulse is 1,2/50 µs
NOTE The lightning impulse is defined by the two figures that give these durations in microseconds (µs); in
particular the standard lightning impulse is 1,2/50 µs.[IEC]
lightning impulse withstand voltage lightning impulse voltage that an insulator under prescribed conditions of test will withstand when the insulator is dry
lightning protection system (external) group of measures that are applied to the outside of a structure, and that involve so-called lightning conductors (air terminations), earthing conductors (down conductors) and earth points (earth terminations), in order to limit the damaging effects of lightning to the structure and to provide a pre-determined path for lightning discharge
lightning protection system (internal) group of measures that are applied to the volume inside a building, to render the electromagnetic environment more benign
NOTE This usually involves the creation of equipotential platforms and lightning protection zones.
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lightning protection zone (LPZ) volume in which the lightning electromagnetic environment, in terms of conducted surges and radiated fields, is defined, quantified and managed. The boundaries between zones are established by suitable screening and bonding measures and by surge protective devices
NOTE The following lightning protection zones are characterized by significant changes of the electromagnetic conditions at their boundaries:
a) LPZ 02: possible direct lightning strikes, and unattenuated electromagnetic fields, for example a zone with exposed conductors outside a structure;
b) LPZ 08: no direct lightning strikes, but unattenuated electromagnetic fields can occur, for example a zone with buried conductors or screened cables outside a structure;
c) LPZ 1: no direct lightning strikes, but currents on conductive parts and electromagnetic fields are attenuated with respect to LPZ 0A and LPZ 08, for example a zone inside a structure; and
d) LPZ 2: no direct lightning strikes, but currents in conductive parts and electromagnetic fields are attenuated with respect to LPZ 1, for example a protective zone inside a structure, such as a computer room.
limit range of operation extreme conditions that an operating instrument can withstand damage to and without degradation of its metrological characteristics when it is subsequently operated under its rated operating conditions
limited purpose switch switch which complies only with one or more but not with all service applications of a general purpose switch [IEC]
limits of intrinsic error limits of intrinsic error with respect to reference conditions
limits of variations limits of variations with respect to rated operating conditions
NOTE These can be indicated by assigning an accuracy class to an instrument whereby the limits are implicit in the classification. For example, a class 2 instrument has a limit of intrinsic error not exceeding 2 %.
line (overhead line) overhead feeder, including the supports and the cable (where provided) between the terminal supports and the station apparatus
line device connecting two points for the purpose of conveying electromagnetic energy between the them
NOTE 1 Electromagnetic energy may be extracted from or supplied to a line at an intermediate point.
NOTE 2 Examples of lines are two-wire line, polyphase line, coaxial line, waveguide.
line (overhead line) arrangement of conductors, insulating materials and accessories, supported above ground level by structures, for transferring electricity between two points of a system
line post insulator class A insulator where the puncture path of the insulator material is greater than 50 % of the external flashover distance
line voltage drop difference, at a given instant, between the magnitudes of the r.m.s. voltages measured at two given points along a line [IEC]
line (trace or scan) visible or recordable path traced on the screen or target by the moving spot
68 NRS 000-1:2008
link isolator: device provided for the purpose of isolating apparatus from the source of electrical energy
NOTE The term link is deprecated by the IEC, and the term isolator should rather be used.
link (telecommunications) means of telecommunication with specified characteristics between two points
NOTE The type of transmission path or the capacity is normally indicated: for example, line link, radio link, broadband link.
link in a system branch between two nodes of a system [IEC]
NOTE It generally comprises a line, a transformer or a connection between two adjacent busbars.
link stick; operating stick approved insulating rod designed for use at specific voltages to safely operate links, drop-out fuses and other similar equipment
NOTE The term “link” for “disconnector” is deprecated by the IEC.
live electrically charged, or capable of being electrically charged at any time
live adjective describing a studio or other location which has a comparatively long reverberation time
live enclosure live chamber
chamber or enclosed area that contains medium-voltage, high-voltage; extra-high-voltage or ultra-high-voltage apparatus which could be unscreened and could be alive
live part conductor or conductive part intended to be energized in normal operation, including a neutral conductor, but by convention not a conductor that has the function of a protective earth
NOTE This concept does not necessarily imply a risk of electric shock.
live part part of an electrical system that is live under normal operating conditions
live tester device used to determine whether a conductor is live or dead by making physical contact with the conductor
live work activity in which a worker makes contact with the energized live parts or penetrates inside the live working zone with either parts of his or her body with tools, equipment or devices being handled
NOTE 1 Examples of live working include maintenance, connection and disconnection operations.
NOTE 2 The live working is performed using specific methods: hot-stick working, insulating glove working, bare hand working.
live work generic term indicating the various working methods used to carry out maintenance, including connection and disconnection operations on electrical installations while in service
live work declaration printed form that contains declarations and clearance sections for the authorization of all live work to be done on live, operational apparatus in terms of the regulations
69 NRS 000-1:2008
live work warning notice portable warning notice that is provided to indicate that live work is in progress on apparatus or to indicate any special operating condition in force (or both), on any panel or circuit whilst live work is in progress
live working generic term indicating the various working methods used to carry out maintenance, including connection and disconnection operations on electrical installations while in service [IEC]
live working (live work) activity in which a worker makes contact with energized live parts or penetrates inside the live working zone with either parts of his or her body or with tools, equipment or devices being handled
NOTE 1 Examples of live working include maintenance, connection and disconnection operations.
NOTE 2 The live working is performed using specific methods: hot stick working; insulating glove working; bare hand working
load device that absorbs power [IEC]
load part of the circuit which lies beyond the output terminal or output reference plane
load (1) device intended to absorb power supplied by another device or an electric power system
load curve graphical representation of the observed or expected variation of load as a function of time [IEC]
load duration curve curve showing the duration, within a specified period of time, when the load equalled or exceeded a given value [IEC]
load factor ratio, expressed as a numerical value or as a percentage, of the consumption within a specified period (year, month, day, etc.), to the consumption that would result from continuous use of the maximum or other specified demands occurring within the same period
NOTE 1 This term should not be used without specifying the demand and the period to which it relates. NOTE 2 The load factor for the given demand is also equal to the ratio of the utilization time to the time in hours within the same period.
load factor factor that allows for the average period in which an appliance uses maximum load, derived by average load divided by the maximum demand
NOTE Power outage hours must be excluded from load factor calculations
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load factor (LF) actual energy supplied (in kWh) over a period divided by the maximum demand in kWh over that period multiplied by the time period selected (i.e. actual energy supplied divided by potential energy supplied). It is always less or equal to unity
load in a system 1) active, reactive or apparent power generated, transmitted or distributed within a system
2) power demanded by a group of consumers classified according to their particulars, and characteristics, e.g. heating load, daytime reactive load, etc.
load range maximum range in amperes over which the meter is designed to operate continuously with a specified accuracy under certain conditions
load reconnect voltage voltage set-point of the regulator at which the loads are reconnected to the battery after load-shed has occurred
load sensing preferred characteristic of an inverter such that if no load is connected to the output of the inverter the inverter automatically switches to a standby mode and the input current is minimized
NOTE This avoids unnecessary discharge of the storage battery. The inverter should automatically revert to normal operation when a load is reconnected.
load shedding process of deliberately disconnecting pre-selected loads from a power system in response to an abnormal condition in order to maintain the integrity of the remainder of the system [IEC]
load transfer transfer of signalling traffic from one signalling link to one or more other links
load transfer redistribution of load flow within similar components of the network, due to the failure or risk of failure, of a part of the network [IEC]
0
20
40
60
80
100
0 2 4 6 8 10 12 14 16 18 20 22 24
TIME (HOURS)
DE
MA
ND
(kW
)
A A
B
A
B
Additional potential energy
if the load is constant at MD
Actual energy used per day
BA
BLF
+=
(kVA).PF.1 MD
Energy ActualLF =
MD(kW) = MD(kVA).PF
where PF is the power
factor
MAXIMUM DEMAND
71 NRS 000-1:2008
load-shed voltage voltage at which the regulator is set to disconnect loads to protect the battery from further discharge to prevent premature damage to the battery due to repeated cycles at low states of charge.
NOTE This set-point is set to the voltage when the maximum permitted depth of discharge is reached.
lock-out state of an auto-recloser when it has completed its tripping and closing sequence and is in its final open state
lock-out (final tripping) disconnection of faulty equipment or part of the network after a predetermined number of unsuccessful reclosures
log book book in which all operating or testing procedures or faults are recorded for future reference
long-rod insulator single insulator equal to a number of disk insulators designed for tensile loading to support an overhead line conductor under tension or suspension
long span span exceeding a length of 250 m long-span ADSS ADSS cable up to a span length of 400 m longitudinal redundancy check check digit used to ensure the integrity of the information read from the magnetic stripe on the card
lost call request for a connection which is rejected due to network congestion
lost call telephone call that gets through to the licensee but that is not answered
low frequency (LF) (see NOTE 2) frequency up to and including 9 kHz low-voltage (1) voltage having a value below a conventionally adopted limit
low-voltage (2) lowest of two or more voltages in an apparatus or installation
low-voltage a.c. r.m.s. voltage that does not exceed 1 kV or a d.c. voltage that does not exceed 1 500 V
low-voltage (LV) (networks) set of nominal voltage levels that are used for the distribution of electricity and whose upper limit is generally accepted to be an a.c. voltage of 1 000 V (or a d.c. voltage of 1 500 V) [SANS 1019 modified]
NOTE In certain fields of technology, for example motors and mining, voltages up to and including 1 000 V are traditionally regarded as low voltage.
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low-voltage set of voltage levels used for the distribution of electricity and whose upper limit is generally accepted to be 1 000 V a.c.
low-voltage feeder cable the supplier’s three-phase, low-voltage cable to which service cables are connected, through distribution kiosks or meter kiosks, for the purpose of supplying electricity to customers NOTE 1 Feeder cables use a combined neutral and earth system, therefore four-core armoured cables are used.
NOTE 2 In networks that have separate neutral and earth systems, a four-core armoured cable with a separate earth conductor is used.
low-voltage networks lines, cable, switches, protection and associated equipment at voltages below 1 000 V
lower contact load-side contact of a cut-out base, which also allows a removable fuse-carrier or solid-link to pivot
low-reactance current transformer transformer of which a knowledge of the secondary exciting current, secondary winding resistance and turns ratio is sufficient for an assessment of its performance
low-voltage panel mounting plate for meters, moulded case circuit breaker (MCCBs), plugs, and other accessories (but not for busbars)
LPZ 0A possible direct lightning strikes, and unattenuated electromagnetic fields, for example a zone with exposed conductors outside a structure LPZ 0B no direct lightning strikes, but unattenuated electromagnetic fields can occur, for example a zone with buried conductors or screened cables outside a structure
LPZ 1 no direct lightning strikes, but currents on conductive parts and electromagnetic fields are attenuated with respect to LPZ 0A and LPX 0B, for example a zone inside a structure
LPZ 2 no direct lightning strikes, but currents in conductive parts and electromagnetic fields are attenuated with respect to LPZ 1, for example a protected zone inside a structure, such as a computer room
LPZ lightning protection zone (LPZ) volume in which the lightning electromagnetic environment, in terms of conducted surges and radiated fields, is defined, quantified and managed. The boundaries between zones are established by suitable screening and bonding measures and by surge protection devices
NOTE The following lightning protection zones are characterized by significant changes of the electromagnetic conditions at their boundaries.
lug connector that comprises a palm and a connector barrel, for connecting a conductor to an equipment terminal
lug terminal screw-type terminal designed for clamping a cable lug or bar directly or indirectly by means of a screw or nut.
73 NRS 000-1:2008
luminaire apparatus which distributes, filters or transforms the light transmitted from one or more lamps and which includes, except the lamps themselves, all the parts necessary for fixing and protecting the lamps and, where necessary, circuit auxiliaries together with the means for connecting them to the electric supply
made safe de-energized or isolated and earthed as required to allow the necessary work to be carried out without danger
magnetic card electricity dispenser electricity dispenser that incorporates magnetic card token technology as the mechanism for inputting standard transfer specification tokens magnetic card token technology technology that enables entry, by a human, of a standard transfer specification disposable magnetic card token into a device via a magnetic card reader
main and check metering dedicated metering system with two active energy and two reactive energy meters fed from two dedicated CT cores and two (or may be only one) dedicated VT winding(s). (see backup meter: an additional meter installed on the same primary plant as the main meter for the purpose of storing backup data in the event of failure of the main meter)
NOTE The recording equipment should also be duplicated.
main busbar double (or triple) busbar substation, any busbar which is used under normal conditions [IEC]
main circuit all conductive parts of an assembly of switchgear and controlgear included in a circuit that is intended to transmit electrical energy [IEC]
main circuit all conductive parts of a switching device included in the circuit which is designed to close or open
main earth earthing device applied as part of the requirement for the issue of a permit to work
main earthing conductor conductor that maintains earth continuity throughout a cable joint or that connects the earth circuit of a cable to the metallic enclosure of terminal equipment, and that is rated to carry the prospective earth fault current of the system
main and check metering dedicated metering system with two active energy and two reactive energy meters fed from two dedicated CT cores and two (or maybe only one) dedicated VT winding(s) NOTE The recording equipment should also be duplicated. main metering dedicated metering system with one active energy meter, and, depending on the tariff in use, one reactive energy meter and one recorder (where applicable)
NOTE This assembly of meters is fed from one dedicated current instrument transformer core and one
dedicated voltage instrument transformer winding.
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main substation transformer or switching station (or both) on the distribution system
mains cables or overhead lines forming part of the reticulation network
maintenance combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function (IEC)
maintenance history detailed log of all the service details pertaining to an item of plant
maintenance philosophy system of principles for the organization and execution of the maintenance (IEC)
maintenance policy general approach to the provision of maintenance and maintenance support based on the objectives and policies of owners, users and customers (IEC)
major axis axis about which the pole has the greater strength
maloperation; misoperation performance of a device different from that which would be expected [IEC]
manned substation substation which is locally operated by personnel working within the substation [IEC]
manufacturer's identification marks markings that include the manufacturer's name or trade mark and the fitting reference.
marginal costing costing based upon the cost of producing an additional unit of output
mass memory memory in a meter that is used as a load profiling tool and that stores energy values, at regular specified intervals, for later retrieval
mass span portions of the span lengths on either side of the structure that impose a vertical load on the structure
NOTE The maximum mass span that can be supported by the structure is dependent on the strength of the structure and the strength of the supporting hardware, including insulators. The mass span is calculated using the mass per unit length of the conductor supported by the structure.
master station data station that has been designated by the control station to ensure data transfer to one or more slave stations
master station system control and data acquisition (SCADA) central controlling station
master station device that is capable of accessing a number of encoders and transferring data from these encoders
master station station which performs the telecontrol of outstations
master station device that is capable of accessing a number of encoders and meters and transferring data from these devices. Also known as a Data Acquisition System
75 NRS 000-1:2008
master substation manned substation from which remotely controlled substations are controlled [IEC]
maximum allowable ovality maximum allowable ovality of a cable or of its component, which is specified by the manufacturer
maximum capacity of a unit (a power station) maximum power that could be generated by a unit (power station), under continuous operation with all of its components in working order [IEC]
NOTE This power may be gross or net.
maximum continuous operating voltage (or Uc) highest r.m.s. power-frequency voltage that an arrester can withstand continuously
maximum current (Imax) highest r.m.s. value of current at which a meter purports to meet the accuracy requirements
maximum demand highest registered electrical demand integrated for a specified period
NOTE this is typically 5-60 minutes and 30 minutes is normally used as this is close to the thermal constant of transformers and lines.
maximum demand indicator instrument that has a resettable pointer to indicate the maximum demand of the equipment during a specified period
maximum permitted depth of discharge maximum permitted charge depletion chosen to prevent premature damage to the battery
NOTE The maximum permitted depth of discharge is indicated approximately by the battery voltage. A suitable settling time has to be allowed for under open-circuit conditions.
maximum pulse rate number of pulses per second at which a pulse device is nominally rated
maximum simultaneous demand maximum kilowatt or kilovolt-ampere simultaneous demand that is supplied to a group of supply points during a billing period
measurand particular quantity subject to measurement
measurement unit (of a split pre-payment meter) portion intended for mounting in a suitable enclosure in a place inaccessible to the customer. The measurement unit is the metrological portion of the pre-payment meter and may include the load switch
mechanical cable gland metallic bush that seals and secures the cable to the enclosure by mechanical means
mechanical failing load maximum load reached when a string insulator unit or a rigid insulator is tested under the prescribed conditions of test
NOTE Mechanical failing load is commonly used in connection with glass or with porcelain insulators.
medium span span of length 100 m to 250 m
76 NRS 000-1:2008
medium voltage set of voltage levels lying between low and high-voltage
NOTE The boundaries between medium and high voltage levels overlap and depend on local circumstances and history or common usage. Nevertheless the band 30 kV to 100 kV frequently contains the accepted boundary.
medium voltage set of nominal voltage levels that lie above low-voltage and below high-voltage in the range 1 kV less than Un or equal to of less than 44 kV
medium voltage a.c. r.m.s. voltage that exceeds 1 kV but does not exceed 44 kV
medium voltage set of nominal voltage levels that lie above low-voltage and below high-voltage in the range 1 kV less than Un less than 44 kV
medium voltage networks lines, cable, switches, protection and associated equipment at voltages from 1 000 V to 22 kV. Sometimes 33 kV can be considered MV in rural areas
medium voltage to low-voltage transformation networks transformation networks between MV and LV voltages
mesh set of branches forming a loop and containing only one link of a given co-tree
mesh (of a system) arrangement of electric lines forming a closed loop and supplied from several sources [IEC]
mesh substation single busbar substation in which the busbar is formed as a closed loop with circuit-breakers in series within the loop [IEC]
meshed system system or part of a system consisting of multiple meshes [IEC]
metal-clad switchgear metal-enclosed switchgear in which certain components (e.g. circuit-breakers) are arranged in separate compartments that have metal partitions and are intended to be earthed
NOTE This term applies to metal-enclosed switchgear with metal partitions that provide the degree of protection, or a higher degree, and that has separate compartments for the following:
a) each main switching device;
b) components connected to one side of a main switching device (e.g. a feeder); and
c) components connected to the other side of the main switching device (e.g. busbars)
metal-enclosed switchgear and controlgear see switchgear and controlgear – metal-enclosed, which states: switchgear and controlgear assemblies with an external metal enclosure intended to be earthed, and complete except for external connections [IEC]
metal-oxide surge arrester without spark-gaps arrester having non-linear metal-oxide resistors connected in series and/or in parallel without any integrated series or parallel spark-gaps [IEC]
metal-oxide varistor highly non-linear varistor that has a high impedance at power-frequency voltage and a very low impedance to over voltages that exceed the maximum continuous operating voltage
77 NRS 000-1:2008
metal-sheathed cable cable provided with a metal sheath for the purpose of excluding moisture from the conductors and their insulation
meter device for measuring and totalling the variable consumption of a product
NOTE In general a meter consists of a sensor and an integrating device that displays the total consumption in metrological units. [SANS 62051]
meter braking elements part of a meter that comprises one or more magnets and their adjusting devices, and that produces a braking torque by the action of its magnetic fluxes upon the currents induced in the moving elements
meter compartment part of a kiosk where the meters and circuit-breakers or fuse holders (or both) are installed NOTE The customer cables are terminated in the meter compartment.
meter constant value expressing the relationship between the active energy registered by a meter and the corresponding value of the test output
meter constants values that are assigned to a specific meter that quantify the energy output values of that meter
NOTE These constants may apply to pulse outputs, calibration outputs or register values.
meter cover enclosure on the front of the meter, made either wholly of transparent material or opaque material provided with window(s) through which the movement of the rotor can be seen and the register can be read
meter kiosk used to provide a safe and convenient point at which to connect multiple customer cables to the busbar and feeder cable via meters and circuit breakers
meter rotor moving element of the meter on which the magnetic fluxes of fixed windings and of braking elements act, and that operates the registers
meter type particular design of meter, manufactured by one manufacturer, having:
a) similar metrological properties;
b) the same uniform construction or parts determining these properties; and
c) the same ratio of the maximum current to the reference current
meter type designation that is used for defining a particular design of meter, manufactured by one manufacturer, that has similar metrological properties, the same uniform construction of parts determining these properties, the same number of ampere turns for the current winding at the basic current and the same number of volt turns for the voltage winding at the reference voltage, and the same ratio of the maximum current to the basic current
metered demand tariff tariff where a demand charge is applicable to the measured maximum demand
metering equipment associated to measure and calculate the quantities of electricity used
78 NRS 000-1:2008
metering compartment that part of a meter kiosk where the meters and circuit-breakers are installed. The customer connects his cables in the metering compartment metering device device that is capable of calculating, storing and displaying active and/or reactive energy values and real-time information
NOTE These functions may be performed in a single unit or in an assembly of modular components, such as time switches, termination blocks and individual energy meters. A common example is a large power user board.
metering device configuration settings of clocks, registers and memory that can be configured in any way by the user so as to implement switching times, rate registers, display sequences, integrating periods, etc. (see metering device: A device that is capable of calculating, storing and displaying active and/or reactive energy values and real-time information)
NOTE 1 These functions may be performed in a single unit or in an assembly of modular components, such as time switches, termination blocks and individual energy meters. A common example is a large power user board.
NOTE 2 This definition is included to address the confusion of terms. Reference is often made to "programming" the meters by users, whereas what actually occurs is the configuration of meters. The action of changing the configuration of the device is called "configuring".
metering device program code that is executed on the embedded controller or other form of processor(s) that are implemented in the metering device
NOTE This code, usually referred to as the firmware of the meter, is produced by the meter manufacturer and cannot be changed by the user in any way.
metering element device in a meter that carries out the required functions of multiplication of the voltage and current in order to obtain electrical power and integration to obtain energy
metering equipment collection of components in the metering installation NOTE Components include instrument transformers, cables, meters, recorders and any housing and ancillary equipment such as test blocks.
metering information data (unprocessed information), processed information and stored information that relate to metering equipment at the metering point or the point of supply
NOTE Metering information includes the following:
a) Configuration data. It relates directly to the metering device itself. It uniquely describes the processing inherent in the device that converts secondary electrical quantities (voltage and current) into the required measurand;
b) Status data. It relates to the condition of the metering device and the validity of the metering information that originates from it. It could be contained in the information presented at the site interface, or elsewhere in the metering system; and
c) Metering data. It refers to the measurands of energy values (active, reactive and apparent), and the instantaneous values that may be available from the meter.
metering information manipulation system information management system into which metering information is entered, and which is able to produce reports and manipulations on the information according to the needs of the various users of the metering system. The “metering master station” often referred to in practice is a specific implementation of this concept
79 NRS 000-1:2008
metering installation meters, fittings, equipment, wiring and installations, used for measuring the flow of electricity, and that comply with standards
metering point point where energy transfer is measured
NOTE 1 Each point can have kilowatt-hours (import and export) and kilovar-hours (leading and lagging).
NOTE 2 The metering equipment should preferably be installed at the point of supply.
metering site see metering point, which states: point where energy transfer is measured
NOTE 1 Each point can have kilowatt-hours (import and export) and kilovar-hours (leading and lagging).
NOTE 2 The metering equipment should preferably be installed at the point of supply.
mimic diagram; wall diagram arrangement of symbols representing the current state of switchgear and lines of a substation (network) and which may be updateable and may have control functions [IEC]
miniature circuit-breaker circuit-breaker that is usually designed to clip onto a standard mounting rail on a distribution board
minimum approach distance DA minimum distance in air to be maintained between any part of the body of a worker or any conductive tool (or material other than specific live tools) being directly handled, and any part at different potentials NOTE This minimum working distance will vary depending upon the electrical and ergonomic components that are chosen.
minimum safe output of the unit power level below which a unit cannot be maintained in continuous service without risk to, at least, one of its components [IEC]
mini-substation (mini-sub) factory assembled and tested free-standing unit that is suitable for use in an area accessible to the public, that comprises a transformer, an equipped medium-voltage compartment and an equipped low-voltage compartment and that is suitable for connection to under-ground cables
minor work that entails the installation of line or cable that does not exceed a distance of 2 km or the excavation of less than 3 m of ground
minor axis axis about which the pole has the lesser strength
modifications from manufacturers changes made to an item to incorporate developments after manufacture
modular design compartments and transformer provided in a "modular" design are constructed to be dismountable. The compartments shall be so designed and assembled that the transformer can be removed in its entirety without appreciable disturbance of the MV and LV compartments. Conversely, the compartment housings shall be removable, after removal of the common roof, without disturbance of the transformer, the contents of the compartments or the underground cables.
modular process course of actions or proceedings consisting of standardized parts or independent units
80 NRS 000-1:2008
module removable plug-in unit generally with a front panel, and designed to be introduced into a crate
module smallest complete environmentally protected assembly of interconnected solar cells [IEC]
modulo-2 addition binary addition with no carry, giving the following values: 0 + 0 = 0; 0 + 1 = 1; 1 + 0 = 1; 1 + 1 = 0. moisture content moisture dissolved in oil and measured in parts per million
NOTE 1 The moisture content of oil can be measured in milligrams per kilogram.
NOTE 2 The insulating value of oil is decreased with the presence of moisture. Moisture can originate from various sources, both internal and external.
monopolar d.c. link link having only one energized pole whatever the means of return of the d.c. current [IEC]
monthly capital charge monthly repayment of the required capital contribution outside of the tariff where the utility provided a customer with financing
moulded-case circuit-breaker (MCCB) circuit-breaker that has a supporting housing of moulded insulating material forming an integral part of the circuit-breaker [IEC]
mounting L-bracket (of an outdoor distribution cut-out) device used to facilitate the mounting of a cut-out on either a wooden cross-arm or a steel cross-arm
multi-drop protocol facility that supports the linking of more than one slave device on the same communication link
multipair cable cable that consists of a number of pairs of insulated conductors
multiple channel instrument instrument, the input circuit(s) of which is/are intended for connection successively to different external circuits by cyclic switching
multiple-point earthing earthing of the protective conductor at points on the distributor in addition to the source earthing of the medium-voltage/low-voltage transformer neutral point
multiplication ratios ratios that are used to transform meter constants from secondary to primary quantities
NOTE Multiplication ratios are the product of the VT ratio and the CT ratio.
multi-rate meter energy meter that is provided with a number of registers, each becoming operative at specified time intervals corresponding to different tariffs [IEC]
mutual induction electromagnetic induction in an electrical circuit arising from the current flowing in another circuit
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mutual induction electromagnetic induction in a tube of current due to variations of the electric current in another tube of current
medium-voltage equipment earth continuous earth that has the combined effect of bonding metal tanks of transformers, switchgear, surge arresters and all metalwork supporting or enclosing medium-voltage apparatus, including the sheaths and armouring of medium-voltage cables and any continuous earth conductors associated with the medium-voltage system, to an earth electrode, direct
naphthenic, paraffinic or aromatic insulating oil dependent on the relative proportions of the three molecular types, each of which conveys its own properties of the finished product
NOTE Oil consists of hydrocarbon mixtures of three main types, i.e. naphthenes, paraffins and aromatics as well as small quantities of sulfur, nitrogen and oxygen.
narrow face pole face through which the minor axis passes
National Electricity Regulator see regulator, which states: independent electricity regulating authority that is established by the government of the day, referred to as the National Electricity Regulator (NER)
net capital contribution due net amount required from applicants as obtained by deducting the tariff capital allowance from the capital contribution due
network electrical infrastructure over which energy is transported from source to point of consumption
network capacity maximum technical limit of load that can be delivered by a particular network before equipment life would be abnormally reduced
network capital costs costs incurred through once-off expenditure on plant equipment and other productive resources
network splitting (islanding) process whereby a power system is split into two or more islands
NOTE Islanding is either a deliberate emergency measure, or the result of automatic protection or control action, or the result of human error.
network splitting; islanding (USA) emergency measure comprising the division of a power system into subsystems in each of which there is an attempted balance between generation and load to achieve isolated operation [IEC]
network strengthening/upgrading/augmentation costs capital expenditure required to increase the capacity of the network to be able to meet increased demand or capacity required on the network
network/wires charges monthly tariff charges that are unbundled to reflect the costs associated with networks (wires) and are usually based on the utilized capacity of the supply
network refurbishment costs major capital expenditure that is required to existing network equipment after the end of its technical life which is required to extend the life of the asset to an age similar to when it is new
network upstream costs costs that have to be incurred further away from the point of supply into the utility network
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neutral designation of any conductor, any terminal or any element connected to the neutral point of a polyphase system [IEC]
neutral conductor conductor connected to the neutral point of a system and capable of contributing to the transmission of electrical energy
neutral point connection means of electrical connection of the neutral point to earth [IEC]
neutral point displacement voltage voltage between the real or virtual neutral point and the earth [IEC]
neutral point in a polyphase system common point of the windings in star-connected equipment such as a power transformer, or an earthing transformer [IEC]
neutralization value acidity total acid number indication or measure of the acidic constituents or contaminants in the oil
NOTE High acidity levels will promote the degradation of the paper and will induce corrosion in the transformer. The presence of acids is normally an indication of oxidation of oil.
new oil virgin oil or oil that has never been used in electrical equipment and that complies in all respects with SANS 555
node point, line or surface in a standing wave where some specified characteristic of the wave field has essentially zero amplitude
NOTE 1 In practice, this amplitude is generally not zero but simply a minimum. The node are then said to be partial.
NOTE 2 The appropriate modifier should be used before the word "node" to signify the type that is intended; e.g. displacement node, particle velocity node, sound pressure node.
node telecommunication network, any point where two or more links are interconnected
node end-point of a branch connected or not to one or more other branches
node point of common connection of consumer service conductors to a feeder, or a branch point in a feeder
node (panel point) point of concurrence of several members in a tower
nominal discharge current of an arrester (In) peak value of lightning current impulse, which is used to classify an arrester [IEC]
nominal power designated power of a device, expressed either in watts (W) or in volt-amperes (VA) and reflected on a nameplate
nominal system voltage suitable approximate value of voltage used to designate or identify a system
nominal voltage declared r.m.s. phase-to-phase voltage of the supply to which the equipment is connected
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nominal voltage of a system; nominal voltage suitable approximate value of voltage used to designate or identify a system [IEC]
nominal circuit voltage; circuit insulation voltage highest circuit voltage to earth on which the instrument will be used and that may be used to determine its insulation test
non-coincident approach network cost allocation method based on using the summated individual maximum demand requirements of customers as opposed to the maximum simultaneous demand of customers
non-directional protection protection that operates when a fault occurs on either side of a given reference point
non-grid supply of electricity that is not provided by means of the conventional generation, transmission and distribution of electricity
NOTE Sources and systems of non-grid supply include, but are not limited to photovoltaics, wind generation, micro hydro, systems, etc.
non-grid service provider authorized supplier of non-grid services
non-load-breaking connector bushing and its associated premoulded elbow connector, which cannot be removed safely while a load is being carried
non-PCB oil, including oil in electrical equipment and in any item of equipment, that has a measurable PCB concentration of less than 20 ppm
non-technical losses losses that arise from theft
non-technical losses generally due to theft, faulty meters, billing errors, etc and calculated by subtracting technical losses from total losses
non-volatile memory storage device that can retain information in the absence of power [IEC]
NOTE The information is retained for a period of at least three months.
normal operating (PV) cell temperature temperature of a photovoltaic cell when subjected to an irradiance of 800 W/m squared, an ambient temperature 20 °C, and a wind velocity of 1m/s
normalized coincidence factor (NCF) factor used to account for the loss of diversity between customers as the number of customers on the distributor diminishes from 1000
1.0 DF(N)
DF(1000) =
CF(1000)
CF(N) = NCF(N) and 1.0 = NCF(1000) ≤
i.e. the NCF = 1,0 for 1000 customers and the NCF(N) for less than 1000 customers is greater than 1,0 and is a maximum for 1 customer.
normative elements elements setting out the provisions to which it is necessary to conform in order to be able to claim compliance with the specification
84 NRS 000-1:2008
notified maximum demand contracted maximum demand notified in writing by the customer for a specific period and accepted by the utility as that which the customer requires
number of cells in a battery number of series-connected cells which make up the complete battery
nxx corresponding location in the reduced network diagram (RND). The replacement costs of each asset category of the RND should be determined according to the RND of the specific utility. This table is drawn up in accordance with the specified RND
object person or a conductive item in contact with a person
object defined function within a protocol
occurrences see events (occurrences) which states: events that are detectable by the sectionalizer control and that represent the fault conditions against which the power line is to be protected
odd harmonics see voltage harmonics
off-load switching device switch that is only capable of making or breaking a circuit when no current is flowing
OHS Act, 1993 Occupational Health and Safety Act, 1993 (Act 85 of 1993)
one-way function function y = f(x) that is relatively easy to compute, but the inverse of which is much more difficult to compute (in other words, given x, it is easy to find y, but given a value y it is difficult to find any solution x of y = f(x))
on-line available data data that is available in the active operational metering database
NOTE This data is normally part of the (DAS) data acquisition system.
on-load switching device switch that is capable of making and breaking a limited flow of electric current
on-site own site site, road or property that belongs to the owner of a particular item of electrical equipment
opening; tripping opening of a circuit-breaker by either manual or automatic control of protective devices [IEC]
NOTE The expression tripping of a network item (line, transformer) in fact means tripping of the associated circuit-breakers.
open-type substation substation in which the insulation to earth and between phase conductors is mainly provided by air at atmospheric pressure and in which some live parts are not enclosed [IEC]
NOTE An open-type substation may be indoor or outdoor.
operating switching, isolating, safety testing, or earthing
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operating authority form printed form that is used for detailing, in writing, the extent of authorization of authorized persons in terms of these regulations
operating diagram wall diagram or electronic diagram in a control centre or control room to indicate the operating position and status of all apparatus
operating diagram permanent or electronic diagram in a control centre or control room, to indicate the operating position and status of all apparatus
operating instruction form printed form that is used to record operating instructions issued by the controller in relation to the operation of electrical apparatus
operating procedure form printed form used to record the operating instructions that are authorized by the controller and that are related to the operation of electrical apparatus
operating stick; link stick insulating rod that is designed and approved for use at specific voltages to operate links and drop-out fuses with safety
NOTE The term "link" used for a disconnector is deprecated by the IEC.
operating voltage operating voltage of a cable is defined by the ratio of the power frequency r.m.s. voltage between phase and neutral or earth, and the power frequency r.m.s. voltage between phases
operating voltage (in a system) value of the voltage under normal conditions, at a given instant and at a given point of the system [IEC]
NOTE This value may be expected, estimated or measured.
operational earthing earthing of a point in the electrical circuit of equipment (e.g. the neutral point) which is necessary for correct operation of this equipment and/or the system [IEC]
optical ground wire earth wire conductor with optical fibres embedded within a steel or aluminium earth wire. It must be able to carry both lightning strikes and fault currents without detrimental effect to the optical fibre telecommunication facilities
optical port infra-red communications port
origin integrity corroboration that the source of data received is as claimed
out of commission state of any apparatus that has been taken out of service and is not available for immediate use.
outage; unavailability state of an item of being unable to perform its required function [IEC]
outdoor distribution cut-out drop-out vented expulsion fuse-link assembly or solid-link assembly, together with the associated components
86 NRS 000-1:2008
outdoor substation substation which is designed and installed to withstand external weather conditions [IEC]
outdoor termination termination that is intended for use where it is exposed to either solar radiation or weathering (or both) [IEC]
outer sheath extruded protective covering applied to a cable
outer sheath non-metallic sheath applied over a metallic covering, such as armouring, constituting the outermost sheath of the cable
outer sheath (oversheath) non metallic sheath applied over a covering, generally metallic, ensuring the protection of the cable from the outside
NOTE 1 In North America, the term sheath is generally used for metallic coverings, whereas the term jacket is used only for non-metallic coverings.
NOTE 2 In case of special bonding, the oversheath may provide electrical insulation of the underlying conducting covering.
outgoing pertaining to traffic at a point of a device or network to indicate that the direction of the call set-up is from that port to another point
outgoing (incoming) feeder in a substation, a feeder bay which is normally used to transmit power to the system (receive power from the system) [IEC]
ovality It is a percentage ratio of diameters according to: (d1 – d2) / (d1 + d2) % where d1 is the maximum measured diameter of the cable and d2 is the minimum diameter of the cable measured at the same cross-section as d1
overall accuracy difference between the measured energy and the true energy, expressed as a percentage of the true energy
overcurrent current exceeding the rated current
overcurrent current of a value exceeding the highest rated value [IEC]
overcurrent any current exceeding the rated value. For conductors, the rated value is the current-carrying capacity
overhaul work done with the objective of repairing or replacing parts which are found to be out of tolerance by inspection, tests, examination, or as required by the manufacturer's maintenance manual, in order to restore the item to an acceptable condition
overhead earth wire; ground wire (USA) conductor connected to earth or lightly insulated, usually installed above the phase conductors of a line or a substation to protect them from lightning strikes [IEC]
overhead line electric line whose conductors are supported above ground, generally by means of insulators and appropriate supports [IEC]
87 NRS 000-1:2008
overhead line line with one or more conductors or a cable supported above ground by appropriate means
NOTE 1 An overhead line may consist of only one conductor when the circuit is closed by the earth.
NOTE 2 An overhead line may be constructed with bare conductors, generally supported by insulators, or with insulated conductors.
NOTE 3 The concept of overhead line generally includes the supporting elements.
overhead line system consisting essentially of overhead lines. [IEC] (see also power line which states: an overhead line that is erected to convey electrical energy for any purpose other than communication, but that excludes the overhead contact or catenary wires of an electric traction system)
overhead service connection overhead conductor between an LV distributor and the consumer’s electrical installation
overhead system system consisting essentially of overhead lines [IEC]
NOTE Certain overhead lines can also be constructed with insulated conductors.
oversheath non metallic sheath applied over a covering, generally metallic, ensuring the protection of the cable from the outside
overturn span (of an overhead line maximum span length capability of the structure foundation under maximum wind load conditions with the statutory foundation factor of safety (currently 2)
overvoltage any voltage, between one phase and earth or between phase conductors, that has a peak value exceeding the corresponding peak value (Um √2 or Um √2 respectively) of the highest voltage for equipment [IEC]
per unit (p.u.) voltage (phase to earth) theoretical unit of voltage equal to the peak value of the maximum system voltage with reference to earth
NOTE 1 p.u. = Um √2�√3 kV.
pair
in telecommunication, uniform line consisting of two conductors
pair two insulated conductors twisted together
panel group of modules fastened together, pre-assembled and wired, designed to serve as an installable unit in an array and/or sub-array [IEC]
panel (of radiating elements) rigid assembly consisting of an array of radiating elements supported by a reflecting plane
panel; bay apparatus in the same circuit situated on one or more floors in a building or buildings or throughout a structure, from and including the busbar isolators
88 NRS 000-1:2008
paper cable single-core and three-core, mass impregnated non-draining (MIND) paper-insulated, lead-sheathed, electric cables
parallel groove clamp bolted connector that has parallel grooves and that accommodates two conductors that could be of similar or of different sizes and materials
parent key key used to encrypt a child key for the purpose of concealing the child key, in order to prevent its undetected modification or unauthorized use (or both)
partially insulated enclosure unfilled enclosure in which the cable cores only are fully insulated for the appropriate insulation level
PCB any one of a number of 209 congeners containing one to ten chlorine atoms attached to a biphenyl group, and are synthetic products not known to occur naturally
NOTE New oil produced from crude oil does not contain PCB.
PCB contaminated item equipment (e.g. transformer, electric motor, pump or pipe) or container (e.g. package, can, bottle, bag, barrel, drum, tank) or any other device that contains PCB or the surfaces of which have been in contact with PCB (the PCB being at a concentration of between 50 ppm and 500 ppm), or any article (e.g. container, oil, water, soil, personal protective equipment) that has been in contact with PCB or PCB contaminated equipment
PCB item any item that has a measurable PCB concentration equal to or exceeding 500 ppm
PE conductor protective (earth) conductor that is separate from the neutral conductor
peak load maximum value of load during a given period of time, e.g. a day, a month, a year [IEC]
peak load set generating set whose purpose is to nun under discontinuous load conditions and to respond rapidly to peaks in the power demand of the network [IEC]
PEN conductor conductor that functions as both a protective conductor and a neutral conductor
percentage depth of discharge amount of charge removed from a fully charged battery at a specified discharge rate, expressed as a percentage of the battery’s rated capacity
NOTE 1 The removal of 25 Ah at the specified discharge rate applicable to the rating of the battery from a
fully charged 100 Ah rated battery results in a 25 % depth of discharge (DOD)
NOTE 2 One hundred per cent DOD means fully discharged; zero percent DOD means fully charged.
percentage error
the value that is obtained by the following formula:
100 x E
E E
error Percentaget
tm −=
where
Em is the energy registered by the meter and Et is the true energy
89 NRS 000-1:2008
NOTE Since the true value cannot be determined, it is approximated by a value with a stated uncertainty that can be traced to standards agreed upon between manufacturer and user or to national standards.
periodic testing testing done according to a predetermined maintenance schedule, with reference to standard maintenance procedures and with the aim of ensuring correct operation of the metering installation
permanent fault fault which affects a device and prevents its restoration into service until action has been taken at the point of the fault [IEC]
permanently manned substation substation which is continuously controlled by personnel who are stationed at the substation [IEC]
phase designation of any conductor, bundle of conductors, terminal, winding or any other element of a polyphase system, which is intended to be energized under normal use [IEC]
phase to earth (line to ground voltage) voltage between phase and earth
phase to neutral voltage voltage between a phase in a polyphase system and the neutral point [IEC]
phase-to-neutral voltage (deprecated) voltage between a line conductor and the neutral conductor at a given point of an a.c. circuit
phase to phase voltage voltage between phases [IEC]
phase-to-earth voltage voltage between phase and earth [IEC]
phase-to-earth voltage (deprecated) voltage between a line conductor and reference earth at a given point of an electric circuit
phase-to-neutral voltage voltage between a phase in a polyphase system and the neutral point [IEC]
phase-to-phase voltage (deprecated) voltage between two line conductors at a given point of an electric circuit
photoelectric control unit device that comprises a photoelectric sensor that responds to variations in illuminance and that is combined with a means of switching an electric load
physically secure environment environment in the form of a facility, enclosure or device the penetration of which, in any manner, actively renders unintelligible any secret data contained therein, or that itself precludes any penetration that could allow disclosure of secret data
pick-up setting expression which is a variable used to indicate sensitivity activation level of a protection device
piggyback system system where more than one high-voltage line of different voltages are supported on the same structure. This term excludes double circuit structures and high-voltage structures carrying low-voltage conductors.
pin connector connector that has a solid cylindrical stub at one end and a connector barrel at the other end
90 NRS 000-1:2008
planned interruption interruption that occurs when a component is deliberately taken out of service (by the utility or its agent) at a selected time, usually for the purpose of construction, preventative maintenance or repair
planned outage outage scheduled in advance, for maintenance or other purposes
planned outage; scheduled outage outage due to the programmed taking out of service of an item [IEC]
planning level level to which a utility designs its networks when it evaluates the impact on the supply system of all loads connected to the system. These levels might change from network to network, depending on network structure and circumstances, and are typically lower than the compatibility level
planning level level to which a licensee designs its network when it evaluates the impact on the supply system of all loads connected to the system NOTE This level can differ from network to network, depending on the network structure and circumstances, and is typically lower than the compatibility level. Recommended planning levels are provided in NRS 048-4. plug-in type separable connector separable connector in which the electrical contact is made by a sliding device
PMRTU remote terminal unit that is designed for pole mounting and that operates specific pole-mounted equipment remotely
point of common coupling point of a power supply network, electrically nearest to a particular load, at which other loads are, or may be connected
NOTE 1 These loads can either be devices, equipment or systems, or distinct customer's installations.
NOTE 2 In some applications, the term "point of common coupling" is restricted to public networks.
point of common coupling PCC point in a network where more than one customer is connected or will be connected. The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points
point of common coupling point in a network where more than one customer is connected or will be connected
point of control point at which the electrical installation on or in any premises can be switched off by a user or lessor from the electricity supplied from the point of supply [Regulation R1, OHS Act]
point of metering point on a distribution or reticulation network at which the metering, or the current and voltage transformers supplied for metering, are located
point of supply point at which the electrical installation of a customer (on any premises) is connected to the distribution system of the licensee (undertaker) [Electricity Act,1987 (Act No. 41 of 1987) modified].
91 NRS 000-1:2008
NOTE Words in brackets are used in the Act –new text in italics.
point of supply point at which electricity is supplied to any premises by a supplier [Regulation R1, OHS Act]
point of supply point in the electrical system where the technical and commercial criteria of supply are specified
NOTE The point of supply may be different from the boundary between the supply system and the consumer's own installation or from the metering point.
point of supply physical point on the electrical network, where electricity is supplied to a customer or where the customers network connects to that of the utility
pole (of a d.c. system) designation of a conductor, terminal or any other element of a d.c. system which is likely to be energized under normal conditions; e.g. positive pole, negative pole [IEC]
pole (of equipment) certain types of equipment such as switchgear, the part corresponding to one of the phases in a.c. or to one of the polarities in d.c. [IEC]
NOTE According to the number of poles within the equipment, it is called: single-pole equipment, two-pole equipment, etc.
pole pike device that is used to assist the manual erection of poles. The top end usually consists of an aluminium tube of diameter approximately 75 mm, with the lower end being flat with a pair of handles
NOTE For the erection of wooden poles, a single pike or a pair of pikes secures the pole during erection and backfill operations.
pole-mounted remote terminal unit pole-mounted terminal unit that operates specific pole-mounted equipment remotely
pole-mounted remote terminal unit remote terminal unit that is designed for pole mounting and that operates specific pole-mounted equipment remotely
pole-mounted substation outdoor distribution substation mounted on one or more poles [IEC]
poles (number of) (number of) conducting paths between the interior of the enclosure and the electrical equipment (e.g. a transformer), which may be one, two, three or four, depending on the number of bushings
pole-top make-off preformed fitting designed to secure a component to the top of a pole
portable earthing device portable appliance provided for connecting to earth a circuit or apparatus that is isolated
portable working standard standard instrument that has been calibrated at an approved calibration laboratory or approved test house and is designed for calibrating metering equipment in the field
post insulator insulator intended to give rigid support to a live part which is to be insulated from earth or from another live part
NOTE A post insulator may be an assembly of a number of post insulator units.
92 NRS 000-1:2008
post insulator (in air filled enclosures) structure supporting one or more conductors, and insulating it or them from the point on the enclosure to which the structure is attached, including the means of attachment
NOTE It follows that such an enclosure might be self contained and removable; it might also be a compartment of the connected equipment and therefore an integral feature of that equipment; it might also be a stand-alone item of equipment, for example a junction box.
post insulator (in junction boxes) structure that supports one or more conductors, and that insulates it or them from the point on the enclosure to which the structure is attached, including the means of attachment
potential gradient potential difference per unit length (usually expressed in volts per metre, V/m) measured in the direction in which the potential difference is at a maximum
pour point point at which oil loses its liquid properties
NOTE This property is important in cold climates, where the oil still needs to flow freely and serve its purpose as an insulant.
power cable cable designed for application in electrical power distribution networks power demand from the system power which has to be supplied to the system in order to meet the demand [IEC]
power equipment enclosure that contains live power line conductors power factor ratio of the watts in a system to the voltage ampere load
power factor ratio of the watts in a system to the volt-ampere load
NOTE It is usual to calculate the average power factor as kWh divided by kVA multiplied by 1 divided by T where T is the integration period in hours.
power factor ratio of the (real) power to the apparent power power factor ratio of the total power (in watts) dissipated in an electric circuit to the total equivalent volt-amperes applied to that circuit
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power factor (PF) real active power in kW divided by the apparent power in kVA i.e.
power/frequency control secondary control of the active power of generating sets in response to variations in system frequency and to the variations in the grand total of active power exchanged with the interconnected systems [IEC]
power frequency; frequency frequency of alternating voltage generated by power system generators
power frequency; frequency conventionally, the values of frequency used in the electricity supply systems [IEC]
power line arrangement of electrical conductors, insulating materials and accessories for transferring electricity between two points of a system, which is supported above ground level by structures
power line overhead line that is erected to convey electrical energy for any purpose other than communication, but that excludes the overhead contact or catenary wires of an electric traction system. (see also overhead line which states: An overhead line that is erected to convey electrical energy for any purpose other than communication, but that excludes the overhead contact or catenary wires of an electric traction system)
power outage recording recording dates, times and reasons for power outages
power rating designed power output of an item of equipment as stated on its rating plate under the specified conditions, measured in kilowatts (kW)
Q (kVAr) jQ(kVAr) p(kW)S(kVA)
)COS(S(kW)
P(kW)PF
+=
== Φ
PF = cos φφφφ
φφφφ
S (kVA)
P (kW)
94 NRS 000-1:2008
power station installation the purpose of which is to generate electricity and which includes civil engineering works, energy conversion equipment and all the necessary ancillary equipment
NOTE The power station includes all the equipment up to the point where energy is ready for
transmission or distribution. It could, or need not include any substation situated within the
precincts of the power station.
power station; electrical generating station installation whose purpose is to generate electricity and which includes civil engineering works, energy conversion equipment and all the necessary ancillary equipment [IEC]
power system power stations, feeders, substations and apparatus whereby electrical energy is made available to the customers' points of supply
power system frequency fundamental frequency frequency of alternating voltage generated by power system generators
NOTE synonymous with “fundamental frequency” as defined in SANS 61000-4-30.
precision repeatability of measurement data, customarily expressed in terms of standard deviation
preferred most desirable from a selection of options, unless otherwise specified
premium supplies supplies with features specifically contracted with the customer whether it is the same or different features to the standard set by the particular utility on a specific network
prepayment meter energy meter provided with a mechanism which, by insertion of suitable payment means e.g. (coin, token, credit card), connects a supply of electricity and then disconnects it after the consumption of a predetermined amount of energy or after a predetermined duration
prepayment meter electricity meter (hereinafter referred to as a meter) that can (by means such as tokens, cards, keypads) be operated and controlled to allow the flow of a prepurchased amount of energy in an electrical circuit
prepayment metering system whereby a prepayment meter is installed at the consumer’s premises, instead of the credit type Ferraris disc meter
prescription limitation by law of the time within which a claim can be made
pressure relief device of an arrester means for relieving internal pressure in an arrester and preventing violent shattering of the housing following prolonged passage of fault current or internal flashover of the arrester [IEC]
pressure relief rated current continuous current through the arrester that will cause the pressure relief device to operate, thus relieving the internal pressure inside the arrester and preventing violent shattering of the housing
preventive maintenance maintenance carried out at predetermined intervals or according to prescribed criteria and intended to reduce the probability of failure or the degradation of the functioning of an item (IEC)
95 NRS 000-1:2008
primary control (of the speed of generating sets) control of the speed of each generating set by its individual governor which ensures that the driving torque is a function of the system frequency [IEC]
probability distribution function giving the probability that a random variable takes any given value or belongs to a given set of values
probability distribution function (of a sampled load) function that describes the probability that a certain value might appear as the sampled load
NOTE This function is derived from the cumulative distribution function.
programmable metering device device that is capable of calculating, storing and displaying active and reactive energy values according to a user-defined configuration
prohibited area enclosed area, in which live conductors or live parts of electrical apparatus are accessible, and to which access is restricted to specifically authorized persons
project line or cable installations exceeding a distance of 2 km and work that entails detailed planning and project work which generally takes more than a month to complete
protection provision for detecting abnormal conditions in a power system and then initiating signals, indications or clearance of the condition, or a combination of these
protection provisions for detecting faults or other abnormal conditions in a power system, for enabling fault clearance, for terminating abnormal conditions, and for initiating signals or indications
NOTE 1 The term "protection" is a generic term for protection equipment or protection systems.
NOTE 2 The term "protection" may be used to describe the protection of a complete power system or the protection of individual plant items in a power system e.g. transformer protection, line protection, generator protection.
NOTE 3 Protection does not include items of a power system plant, provided for example, to limit over voltages on the power system. However, it includes items provided to control the power system voltage or frequency deviations such as automatic reactor switching, load-shedding, etc.
protection capability ability to perform the functions of a protection relay or protection device
protection device device designated to perform a specific protection function
protective (protection) current transformer current transformer that is intended to supply electrical protective current
protective (protection) device device that is incorporated in an instrument for the purpose of limiting over voltage or over current that can appear in one or more of its components
96 NRS 000-1:2008
protective conductor
conductor provided for purposes of safety, for example protection against electric shock
protective device (capacitor voltage transformer) device incorporated in a capacitor voltage transformer for the purpose of limiting over voltages which may appear across one or more of its components, notably due to error resonance phenomena
protective conductor conductor that forms part of a low-voltage distributor, and that connects the source earth to the consumer's earth terminal. The conductor is also connected to other earth electrodes and exposed conductive parts of the low-voltage distributor. (see also PE conductor which states, a protective (earth) conductor that is separate from the neutral conductor, and protective earth neutral (PEN) conductor which states: a conductor that functions as both a protective conductor and a neutral conductor).
protective current transformer current transformer intended to transmit an information signal to protect and control devices
NOTE The accuracy class of a protective current transformer is designated by its class index followed by the letter P (protection). The class index gives the limit of the absolute value of the composite error at the rated accuracy limit primary current for the class concerned, as a percentage of this current.
protective level of a protective device highest peak voltage value that should not be exceeded at the terminals of a protective device when switching impulses and lightning impulses of standard shapes and rated values are applied under specified conditions
protocol driver software interface code to translate propriety meter code to values that the master station or data acquisition system can utilize
protocol stack defined implementation of the communication layers in a protocol
pulse abrupt variation of short duration of a physical quantity followed by a rapid return to the initial value
pulse variation of physical quantity where a transition from one value to another is followed immediately after some time interval by a return to the initial value
pulse wave that departs from an initial level for a limited duration of time and ultimately returns to the original level
pulse device functional unit for initiating, transmitting, retransmitting or receiving electric pulses, representing finite quantities, such as energy, normally transmitted from some form of electricity meter to a receiver unit. (see pulse: a wave that departs from an initial level for a limited duration of time and ultimately returns to the original level, see pulse initiator: any device, mechanical or electrical, that is used with a meter to initiate pulses, the number of pulses that is proportional to the quantity being measured)
NOTE It may include an external amplifier or auxiliary relay (or both) and see pulse receiver: The units that receive and register the pulses. (see pulse above)
NOTE It may include a periodic resetting mechanism, so that a reading proportional to the demand may be obtained.
97 NRS 000-1:2008
pulse receiver units that receive and register the pulses. (see pulse: wave that departs from an initial level for a limited duration of time and ultimately returns to the original level)
NOTE It may include a periodic resetting mechanism, so that a reading proportional to the demand may be obtained.
pulse recorder device that receives and records pulses over a given demand period. (see demand integration period which states: the interval of time, for example 15 min, 30 min, on which the demand measurement is based [IEC]
pulsing meter unit that forms part of the metering device that houses the metering element and performs the integration function to generate proportional pulses for the measured active or reactive energy (or both)
pulsing unit unit that is mounted in the pulsing meter, that generates the output pulses proportional to the measured active or reactive energy (or both), and that is of a defined time/length
pumped storage operation whereby water is raised by means of pumps and stored for later use in one or more hydroelectric installations for the generation of electricity [IEC]
pumped storage power station hydroelectric power station employing high level and low level reservoirs permitting repeated pumping and generating cycles to be carried out [IEC]
puncture path produced through a solid by a breakdown producing permanent damage. The term is used as a synonym for electrical breakdown in solids
puncture (of an insulator) disruptive discharge passing through the solid insulating material of the insulator which produces a permanent loss of dielectric strength
pure risk risk which results only in loss, damage, disruption or injury with no potential for gain, profit or other advantage p.u. voltage (phase to earth) theoretical unit of voltage equal to the peak value of the maximum system voltage with reference to earth
NOTE 1 p.u. = Um 2 / 3 kV.
qualification procedure number of type tests that are carried out on one meter or a small number of meters of the same type having identical characteristics, selected at random, to verify that the meter type has no serious system abnormalities NOTE The precise tests and the number of meters to be tested are to be agreed upon between the parties.
qualifying symbol symbol added to another to provide additional information
NOTE 1 Qualifying symbols cannot normally be used on their own but a general symbol may sometimes be used for qualifying purposes. Thus the general symbol for an auto-transformer may be added to that for a motor starter to produce the symbol for an auto-transformer starter.
NOTE 2 The term “supplementary symbol” has been used in the past with the same meaning as qualifying symbol.
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quality fitness for purpose of a product or service
quality assurance everything that must be done to ensure the quality of a product or service
quality control verification of quality
quality of supply (QOS) appraisal of the deviations of technical criteria outside a defined range (explicit or implicit) of the electricity supply or of the aggregate of electricity supplies within an electrical system [IEC]
quality of supply (QOS) technical parameters to describe the electricity supplied to customers, and that are used to determine the extent to which the needs of customers are met in the utilization of electricity
NOTE Sometimes used synonymously with “power quality”, which is defined as the “characteristics of the electricity at a given point on an electrical system, evaluated against a set of reference technical parameters.” [SANS 61000-4-30]
radial feeder see single feeder, which states: electric line supplied from one end only [IEC]
radial system system or part of a system consisting of single feeders supplied from a single source of supply [IEC]
range-taking accessory accessory that is designed to accommodate more than one size of cable
rapid protection operation protection function that enables rapid breaker operation, be it an instantaneous protection function (i.e. operation with no intentional time delay), a fast curve protection function, or an instantaneous function with a relatively short definite time delay
rapid voltage change changes in the magnitude of the supply voltage that occurs within the order of milliseconds
rate period period of the day for which energy values are accumulated and recorded in a specific register
NOTE There are three rate periods for the time-of-use tariffs, namely peak, standard and off-peak.
rated burden value of the burden on which the accuracy requirements of a specification are based
rated capacity of a cell or battery quantity of electricity, declared by the manufacturer, which a cell or battery can deliver under specified conditions
NOTE 1 Typically at a constant discharge current and battery temperature after a full charge. For a current I20 which will fully discharge the battery in 20 h, the rated capacity is abbreviated to C20.
NOTE 2 This value is usually expressed in ampere-hours. [IEC]
rated discharge current peak value of lightning current impulse which is used to classify an arrester [IEC]
rated fibre stress stress in the wood from the applied load just before breaking
rated frequency frequency at which the transformer or reactor is designed to operate
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rated frequency frequency of the supply mains in Hertz (Hz) specified by the manufacturer for normal usage of a generator ,and the accessory or associated equipment
rated impulse withstand voltage prescribed peak value of the (switching/lightning) impulse withstand voltage which characterizes the insulation of an equipment as regards the withstand tests [IEC]
rated impulse withstand voltage see basic insulation level, which states: specific insulation level, expressed in kilovolts, in accordance with which the complete system (including the line pole insulation to earth at every pole, the switchgear, the line isolators and reclosers, and the substations connected to the system, including their transformers) is designed and constructed
rated insulation level set of standard withstand voltages which characterize the dielectric strength of the insulation [IEC]
rated insulation level test voltages, under specified conditions, that the insulation is designed to withstand
NOTE These test voltages can for instance :
a) rated lightning impulse and short duration power frequency withstand voltages
b) rated lightning and switching impulse withstand voltage (phase-to-earth).
rated insulation level (b) combination of the rated lightning impulse withstand voltage and the rated short duration power frequency withstand voltage specified in table 2 of SABS IEC 60298
rated knee point voltage knee point voltage on which the performance of class X current transformers is based and which is marked on the rating plate
rated normal current main circuits and switching devices, the r.m.s. value of current that they can carry continuously under the specified conditions of use and behaviour might not have the same value of rated normal current
NOTE Some main circuits of switchgear (e.g. busbars and feeder circuits)
rated normal current for main circuits and switching devices, the r.m.s. value of the current that they are designed to carry continuously under the specified conditions of use and behaviour
NOTE Some main circuits of switchgear, for example, busbars and feeder circuits might not have the same value of rated normal current.
rated peak withstand current main and earthing circuits, the peak current that a mechanical switching device is designed to carry in the closed position under prescribed conditions of use and behaviour
rated peak withstand current for main and earthing circuits, the peak current associated with the first major loop of the short-time withstand current that a mechanical switching device is designed to carry in the closed position under prescribed conditions of use and behaviour
100 NRS 000-1:2008
rated primary current (of a CT) value of the primary current that appears in the designation of a CT and on which its performance is based [IEC]
rated primary voltage (of a VT) value of the primary voltage that appears in the designation of a VT and on which its performance is based [IEC]
rated short-circuit breaking current main and earthing circuits, the r.m.s. value of current that the switching device can carry in the closed position during a specified short time under prescribed conditions of use and behaviour.
rated short-circuit breaking current (of a switch-fuse combination) highest prospective short-circuit current that the combination shall be capable of breaking under the conditions of use and behaviour defined, and expressed by the r.m.s. value of its a.c. component
rated short-time withstand current main and earthing circuits, the r.m.s. value of current that the switching device shall be able to carry the closed position during a specified short time under prescribed conditions of use and behaviour
rated system voltage highest r.m.s. phase-to-phase voltage of the system
rated tensile strength calculated breaking load of the optical ground wire (OPGW) construction
rated time value marked on the rating plate as the time in seconds for which a current transformer will withstand the rated short-time thermal current
rated transformer ratio ratio of the rated primary current to the rated secondary current
rated value value of the measured quantity that corresponds to the upper limit of the effective range
rated voltage highest r.m.s. phase-to-phase voltage of the supply for which the equipment is designed
rated voltage of an arrester (Ur) maximum permissible r.m.s. value of power-frequency voltage between an arrester’s terminals at which it is designed to operate correctly under temporary over-voltage conditions as established in the operating duty tests
NOTE 1 The rated voltage is used as a reference parameter for the specification of operating characteristics.
NOTE 2 The rated voltage is the 10 s power-frequency voltage that is used in the operating duty test after high-current impulses or long-duration impulses. Tests used to establish the voltage rating in IEC, and also in some National Standards, involve the application of repetitive impulses at nominal current with power-frequency voltage applied. Attention is drawn to the fact that the two methods that are used to establish rating do not necessarily produce equivalent values (the resolution of this discrepancy is under consideration).
rated voltage (for accessories) voltage assigned by the manufacturer for a specified operating condition of an accessory
raw data data that is extracted from the meter without any processing/manipulation
raw meter data unprocessed information that is received directly from a metering installation
101 NRS 000-1:2008
reactive energy product of voltage and current and the sine of the phase angle between them integrated over a time period, and that is normally measured in kilovar-hours
reactive energy a.c. system, the captive electrical energy exchanged continuously between the different electric and magnetic fields associated with the operation of the electrical system and of all the connected apparatus [IEC]
reactive energy meter meter that is used for the measurement of reactive energy. (see var hour meter which states: reactive energy meter: An electricity meter that measures and registers the integral, with respect to time, of the reactive power of the circuit in which it is connected
NOTE The unit in which this integral is measured is usually the kilovar-hour.
reactive energy meter instrument intended to measure reactive energy by integrating reactive power with respect to time
reactive-power voltage control voltage control by the adjustment of reactive power generation in a power system [IEC]
real power of a power inverter power measured at the output side of the inverter using a wattmeter of suitable bandwidth
real time clock device that maintains to an acceptable level of accuracy, information describing the date and time of day. This information is maintained irrespective of whether power is supplied to the unit within which the clock is installed
recoverable works work where the costs are always directly recoverable from a customer or where a third party is liable for the cost of such work
NOTE They are never pooled in the tariffs and should not be confused with ‘recoverable costs”.
recycling process of reusing a previously coded secure module, involving recoding under authorization, at the KMC redundancy existence of more than one means for performing a required function (IEC)
reference current of an arrester peak value (the higher peak value of the two polarities if the current is asymmetrical) of the resistive component of a power-frequency current that is used to determine the reference voltage of the arrester
NOTE Depending on the nominal discharge current or the line discharge case (or both) of the arrester, the reference current will be typically in the range 0,05 mA to 1,0 mA per square centimetre of disc area for single column arresters.
reference standard measuring instrument that has been calibrated by an approved calibration laboratory reference voltage of an arrester (Uref) peak value of power frequency voltage divided by 2, that is applied to an arrester to obtain the reference current. The reference voltage of a multi-unit arrester is the sum of the reference voltages of the individual units.
NOTE Measurement of the reference voltage is necessary for the selection of a correct test sample in the operating duty test. [IEC]
102 NRS 000-1:2008
refund of capital contribution amounts repaid to customers where they have previously paid capital contributions for networks which are now utilized by other customers
refurbishing reinstatement of items to their original condition and intended performance with consideration for cost and current technology for the purpose of extending the plants useful life expectancy
regenerated oil reclaimed oil used oil that has been reprocessed to comply in all respects with SANS 555
register term was derived from the visible dial on the face plate of the electromechanical meters, where the register provided an indication of the energy usage. In electronic meters, this term refers to the non-volatile memory locations within the metering device where similar energy usage information is stored
registered maximum demand highest averaged demand measured in kVA or kW, during any integrating period within a designated billing period (usually one month)
regulation document providing binding legislative rules, that is adopted by an authority
regulation difference between the maximum and minimum values of the tube voltage drop of a voltage stabilizer tube within a stated range of anode current. difference between the maximum and minimum values of the tube voltage drop of a voltage stabilizer tube within a stated range of anode current
remediation method of clean up that will ensure a minimum hydrocarbon or synthetic oil presence of 1 000 ppm or 0,1 % above the background level in the case of petroleum products, and 5 000 ppm in the case of mineral-based products
repair that part of corrective maintenance in which manual actions are performed on the item
replacement value value of installing a new system in the year for which calculations are done. These calculations have to be done annually to reflect the present day average costs
reinforcement of a system addition or substitution of some items in a power system (transformers, lines, generators, etc.) so that it will be able to meet an increased load or provide a better quality of supply [IEC]
relative density ratio of the density of a substance to the density of a standard, usually water in the case of a liquid or solid, and air in the case of a gas
relative error ratio of the absolute error to a comparison value
NOTE 1 The term is used in the “true value” approach.
NOTE 2 The comparison value should be a true value of the quantity but, since a true value cannot
be determined, in general, a conventional true value is used.
relative error ratio of the absolute error to the true value of the measured quantity
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relative error ratio of the absolute error to the setting value
relay chamber metal-enclosed chamber that contains control, measuring, indicating, alarm, protective and regulating equipment associated with a switchgear panel
remote station station which is monitored, or commanded and monitored by a master station [IEC]
remote terminal unit telecontrol remote terminal unit which monitors and operates specific equipment remotely
remote terminal unit device that provides an interface between the auto-recloser (AR) and the supervisory control and data acquisition (SCADA) system
remotely controlled substation unmanned substation which is controlled by means of telecontrol devices [IEC]
repair that part of corrective maintenance in which manual actions are performed on the item
reserve busbar double (or triple) busbar substation, any busbar which is used under abnormal conditions. It is generally less well equipped than a main busbar [IEC]
reset time selectable period that starts from a ‘first’ countable event and that represents the period during which the counter will reset to 0 if the countable events remain less than the counts-to-open setting
reset time time that elapses from the instant that the auto-recloser first recloses onto a healthy line to the time that the trip counter resets to zero
reset time user selectable period that is started by an overcurrent pick-up transgression. The reset time may be set to time-out,
a) after a pre-set time;
b) after return of voltage or
c) after the FPI is manually or remotely reset.
reset time time duration after a circuit-breaker close operation for which the measured currents are below a fault detecting level. On expiry of this time the protection sequence resets.
reset time (for elementary relays) time interval between the application of the specified input voltage to a bi-stable relay in the operate condition and the change of state of the last output circuit, bounce time not included
reset time (USA) time after an automatic reclosure, before the automatic reclosing equipment will initiate another reclosure in the event of another power system fault
residual strength remaining tensile strength of the conductor after it has been in service
104 NRS 000-1:2008
residual voltage peak value of voltage that appears on the protected output terminals of an surge protective device during the passage of discharge current
residual voltage sum of the instantaneous values of all three line-to-earth voltages, in a three-phase system
residual voltage voltage equal to the sum of the phase-to-earth voltages
residual voltage (discharge voltage) (Ures) voltage that is maintained between the arrester terminals during the passage of discharge current, and that determines the protective characteristics of the arrester
residual voltage (of voltage dip) minimum value of r.m.s. voltage recorded during a voltage dip
NOTE The residual voltage may be expressed as a value in volts or as a percentage or per unit value of
the reference voltage. [SANS 61000-4-30, modified]
residual voltage winding winding of a transformer between the terminals of which is produced the residual voltage or one of the three component voltages which, when added together, constitute the residual voltage [IEC]
residual voltage; discharge voltage voltage that is maintained between the terminals of an arrester during the passage of the discharge current, and that determines the protective characteristics of the arrester
resistance volume of an earth electrode volume of earth around an earth electrode within which the major part of the potential difference between the electrode and the general mass of the earth occurs
resolution smallest change in a measurand, or quantity supplied, which causes a perceptible change in the indication
resolution (of an instrument) smallest change in the quantity being measured that will produce an observable change in the reading of the instrument. When used in the context of an analogue-to-digital converter, it represents the smallest change in analogue input that will generate a change of one bit
resolution (definition) measure of the sharpness of detail of a television picture
resonant earthed (neutral system) system in which one or more neutral points are connected to earth through reactances which approximately compensate the capacitive component of a single-phase-to-earth fault current
responsible person person who has been authorized in writing to be responsible for ensuring that the work on the electrical apparatus can be carried out with safety
restraint protection parameter limits that prevent sectionalizer operation, for example current inrush and low current restraint
restricted earth fault relay earth fault relay that is unconditionally stable for faults outside the protected zone but that will operate for earth faults above the preset value within the zone
105 NRS 000-1:2008
restricted earth-fault protection protection in which the residual current from a set of three-phase current transformers is balanced against the residual output from a similar set of current transformers or, more usually, from a single current transformer located on the earthing connection, if any, of a neutral point
reticulation system distribution network/system for a specific local distribution area
retrofit modifications done to an item to incorporate improvements in design to ensure enhanced operating performance
revenue protection any steps taken to prevent, minimize, eliminate or recover the loss of revenue owing to theft, non-payment or any other similar causes, for services supplied
ring feeder arrangement of electrical lines forming a complete ring and supplied only from a single source [IEC]
NOTE A ring can be operated open or closed.
ring main electrical supply through cable in a closed ring, providing alternative paths
ring main see ring feeder, which states: arrangement of electrical lines forming a complete ring and supplied only from a single source
NOTE A ring can be operated open or closed. [IEC]
ring main switch switch housed in a ring main unit and connected in a ring main
ring main switchboard single busbar switchboard that can supply a reticulation network and can open or close a section of a ring main
ring main unit switchgear assembly with an external metal enclosure, usually comprising two ring main switches connected in series and a switch or switch-fuse connected to the junction between the ring main switches
ring main unit completely enclosed single busbar unit which forms part of the ring main and contains one or more branch switches
ring main unit switchgear assembly with an external metal enclosure, usually comprising two ring main switches connected in series and a switch or switch-fuse connected to the junction between the ring main switches
ring substation single busbar substation in which the busbar is formed as a closed loop with only disconnectors in series within the loop [IEC]
ringfencing financial separation of the electricity related costs from all other costs incurred within a utility, and the further financial separation of the generation, transmission and distribution costs within the utility
106 NRS 000-1:2008
risk chance of loss, or the probability that an undesired event may occur, multiplied by the cost of that event if it does occur
risk management managerial function which has the objective of protecting people, assets and profits of a business, by eliminating or minimizing the potential for loss from pure risk and the provision of funds to recover from losses that do occur
routine test test made by the manufacturer on each manufactured length of cable to check that each length meets the specified requirements
routine test test that is required to be carried out on every item or batch of items before delivery
routine test test made on each individual device during or after manufacture to check if it complies with the requirements of the standard concerned or the criteria
routine test on a cable test carried out on all finished cable lengths by the cable manufacturer to demonstrate the integrity of the cable
routine tests quality control tests performed during and after manufacturing
run-of-river power station hydroelectric power station, which uses the river flow as it occurs, the filling period of its own reservoir by the cumulative water flows being practically negligible [IEC]
run-to-failure failure of an item, which has intentionally not been subject to preventive maintenance rural clustered or scattered structures, usually of low density, not served by a well established infrastructure (roads, telecommunication, etc.). The power is usually supplied radially by overhead lines emanating from one distribution station.
rural (area) area characterized by clustered or scattered structures, usually of low density, not served by well established infrastructure (roads, telecommunications, etc.)
rural network networks not considered urban
rural networks electrical networks found in areas that are sparsely populated e.g. farming communities; [networks that are not defined as urban (see urban networks)]
rural (networks or system) networks or systems serving clustered or scattered structures, usually of low density, not served by well established infrastructure (roads, telecommunications, etc.). The power network is usually supplied radially by overhead lines emanating from one distribution station.
107 NRS 000-1:2008
SANS 1524-0 definitions in SANS 1524-0 apply
SANS 470 definitions in SANS 470 apply
SANS 780 definitions in SANS 780 apply
SANS 60050 definitions in SANS 60050 chapter 441apply
safe clearance working; hot stick working (USA) method of live working by which the worker remains at a specified distance from the live parts and carries out his work by means of insulating poles [IEC]
safety clearance minimum distance that, for safety reasons, needs to be maintained between any part of a person’s body or any work tool and any unearthed, bare LV conductor or any unearthed and screened MV/HV conductor (see safety clearances)
safety clearances safety clearances are specified according to the rated voltage of the system: rated voltage (r.m.s. phase-to-phase) safety clearance:
up to 11 kV 0,20 m above 11 kV and up to 33 kV 0,43 m above 33 kV and up to 66 kV 0,77 m above 66 kV and up to 132 kV 1,45 m above 132 kV and up to 275 kV 2,35 m above 275 kV and up to 400 kV 3,20 m above 400 kV and up to 765 kV 5,50 m
safety equipment equipment or article, including protective clothing, which is manufactured, provided, installed or used in the interest of safety
safety lock approved lock or suite of locks for which only one single key is available
safety testing testing of apparatus to ascertain whether it is live or dead by means of equipment provided for this purpose
sag maximum vertical distance between a conductor that spans between supports, and a straight line that joins the conductor’s points of support [IEC]
sample test test carried out on a sample of a completed cable or on components taken from a completed cable, at a specified frequency so as to verify that the finished product complies with the design specifications
sample test test on a sample
sample test test made by the manufacturer on samples of complete cable or components taken from a completed cable at a specified frequency, so as to verify that the finished product meets the specified requirements
108 NRS 000-1:2008
sample test test carried out on a sample (of a completed product) or on components thereof so as to verify that the finished product complies with the design specifications
sampling test test on a number of devices taken at random from a batch
satellite substation one of the remotely controlled substations, controlled by a master substation [IEC]
screen (of a cable) conducting layer(s) having the function of control of the electric field within the insulation
NOTE A screen may also provide smooth surfaces at the boundaries of the insulation and assist in the elimination of spaces at these boundaries. [IEC]
screened (equipment) completely surrounded by earthed metal or protected from accidental contact by a fixed barrier of non-conducting material
screened (insulation) insulation that has a surrounding earthed metallic layer to confine the electric field within the insulation.
screened separable connector separable connector, which has a fully screened external surface [IEC]
screened separable connector termination air filled enclosure within which the cable cores are terminated with screened separable connectors
screening electrical screen of non-metallic or metallic material or both covering the insulation
seal passive, one-time locking device, preferably with a unique number or other form of identification that is used to provide a reliable deterrent against tampering and to give an indication of tampering NOTE Tampering can be unauthorized removal or attempted removal. sealed cable (end cap) device placed on the ends of cable to prevent the ingress of moisture during storage, transportation and installation
sealed end termination to the end of the cable providing a seal from the external environment and maintaining the filling within the cable
sealed system box or enclosure that can only be accessed by the customer by removing either a locking device, a series of securing bolts or some other security device
sealing process whereby access to metering equipment is restricted by means of a mechanical seal to deter and identify unauthorized access to such equipment sealing tool device for securing the seal, where required
109 NRS 000-1:2008
secondary control (of active power in a system) co-ordinated control of the active power supplied to the network by particular generators [IEC]
secondary control part of a cascade control, operating with a reference variable, provided by the main controller and with measurement and feedback of subsidiary controlled variables only
secondary distribution distribution system that is normally fed from primary distribution switchgear rather than from transformers
secondary earthing conductor conductor that, for crossed-linked polyethylene (XLPE) insulated cable, connects the copper screen of the cable to the main earthing conductor at a joint or termination
secondary injection passage of a current into a metering circuit at a point beyond the instrument transformer
NOTE This is typically used for the calibration or verification of a metering installation.
sectionalizer device that contains a switch that opens automatically on a downline fault to disconnect a power line during the dead time of an auto-recloser and that is manually operated to close
sectionalizing switch (sectionalizer) switch provided on overhead lines for use in conjunction with an auto-reclosing circuit-breaker for the automatic disconnection of faulty sections of overhead line whilst the line is dead
secure control single non-latching switch that effects one control only. An example of which is either a non-latching switch or two separate push-buttons that effect one state of a control function only in each position. If a control is activated repeatedly it only effects that state and does not change the state of the control
secure control (in the context of auto-recloser (ARC) single non-latching switch that affects one control only
security linking contingency configuration of the network where isolation for maintenance could compromise network stability (i.e. redundancy or firm supply requirements) seed key key used by an algorithm as a starting or initializing value for the generation of another value
selector switch switching device capable of making, carrying and breaking current, combining the duties of a tap selector and a diverter switch [IEC]
selector switch switch for changing the connections from one set of its terminals to another
selector switch disconnector double or triple busbar substation, a disconnector which is intended to connect a primary circuit (line, transformer, etc.) to one of the busbars [IEC]
self-monitoring (fault) condition whereby a fault, that does not cause the system protection to operate, will manifest itself in another way, usually by failure of the consumer’s apparatus to operate
self-restoring insulation insulation which completely recovers its insulating properties after a disruptive discharge [IEC]
110 NRS 000-1:2008
self-supporting aerial bundled conductor multicore aerial bundled conductor system in which all cores are under tension
self-synchronization process of synchronization of an unloaded and unexcited synchronous machine that is excited either at the same time as it is coupled to the system or shortly afterwards [IEC]
sensitive earth fault low level earth fault below 5 A primary current
sensitive earth fault relay relay that is sensitive to very low earth fault currents and in which the operating settings are for current magnitude with a definite time delay
sensitive earth fault sensing arrangement that renders the sectionalizer sensitive to very low earth fault currents
separable connector fully insulated termination that allows the connection and the disconnection of a cable to other equipment
separate neutral and earth cable cable or distributor in which the neutral conductor and the earth conductor are electrically separated from each other
separate neutral and earth (SNE) system where the neutral and the earth conductors are separate at the customer’s installation, but are combined at the source
separation distance minimum distance between power conductors and telecommunication conductors
separator thin layer used as a barrier to prevent mutually detrimental effects between different components of a cable, such as between the conductor and the insulation or between the insulation and the sheath [IEC]
separator (electrochemical) electrochemical cell, device made of insulating material permeable to the ions of the electrolyte and prohibiting totally or partially the mixing of the materials
NOTE Membranes and diaphragms are special forms of separators.
separator (of a battery) material with ion permeable structure to provide electrical insulation between plates of opposite polarity
series capacitor capacitor connected in series with the voltage circuit of a measuring instrument in order to extend its measuring range
series capacitor power capacitor intended to be connected in series with a line
NOTE These capacitors are used primarily for the compensation of all or part of the reactance of the line.
series capacitor device for reducing the impedance of a line to improve the load transfer
series reactor device used for limiting the fault current
111 NRS 000-1:2008
series reactor reactor intended for series connection in a network, either for limiting the current under fault conditions or for load-sharing in parallel circuits
series regulator regulator that prevents overcharging of a battery by disconnecting the photovoltaic current in an array and effectively placing the array in open circuit
NOTE The switching frequency can be high, thus having small voltage sags.
service cable cable that has two or more conductors arranged concentrically within an outer protective sheath
service conductor branch line from the electrical distribution system, to supply one or more customers
service connection branch line from the main distribution system to the point of supply
service connection tapping from a distributor, usually of a smaller cross-sectional area, to supply one or more consumers
service connection tapping from a low voltage distributor, usually of a smaller cross-sectional area, to supply one or more power or telecommunication consumer(s) service connection works equipment that connects the customer to the utility network
service disconnection temporary suspension of service due to non-payment, tampering or cancellation
service distribution box prefabricated box, with or without protective devices, for terminating several service connections to the distribution line(s)
service distribution point generic term for LV distribution boxes, cluster metering boxes, LV kiosks, pillars, pole-boxes, etc., used for supplying consumers from a distributor
service position position of a removable part in which it is fully connected for its intended function [IEC}
service provider entity (individual or organization) that offers a service or services servitude right of entry for the installation, operation and maintenance of a power system given to a supply authority by way of law and registered against the title of the property
NOTE The supply authority pays the land owner for this right depending on the utilization the land.
shared structure structure that supports both power and telecommunication distributors or, a structure which supports both service connections sheath envelope or casing of a conductor
112 NRS 000-1:2008
sheath uniform and continuous tubular covering of metallic or non-metallic material, generally extruded [IEC]
shield barrier or enclosure provided for mechanical protection, which may also have the function of a screen
shield (of a cable) surrounding earthed metallic layer to confine the electric field within the cable or protect the cable (or both) from electrical influence
NOTE Metallic sheaths, armours and earthed concentric conductors may also serve as shields.
shielding; screening conductive covering that surrounds conductors or equipment and that is primarily intended to prevent externally generated interference from impinging on the conductors or equipment
short-circuit accidental or intentional conductive path between two or more conductive parts forcing the electric potential differences between these conductive parts to be equal to or close to zero
short-circuit accidental or intentional connection by a relatively low impedance of two or more points on a circuit which are normally at different potentials [IEC]
short-circuit power product of the current in the short circuit at a point of a system and a conventional voltage, generally the operating voltage
short-circuit protection protective feature that limits the current under short-circuit conditions, to prevent the equipment from being damaged
short span span up to a length of 100 m shrouded conductor conductor in an air-filled enclosure that has additional, unscreened, local insulation enhancement
shrouded insulation termination air-insulated termination that has additional, unscreened, local insulation enhancement typically consisting of bushing protection or taping along with a suitable heat shrink, cold shrink or slip-on cover at the terminal connections
shrouded termination indoor termination that is used in an air-filled terminal box that is insulated but unscreened at the bushing connection
shunt resistor that is connected in parallel with an instrument in order to reduce the current that passes through it
NOTE The resistance may be so chosen that the reduction is a known ratio.
113 NRS 000-1:2008
shunt resistor connected in parallel with the current circuit of a measuring instrument in order to extend its measuring range
NOTE A shunt is generally intended to provide a voltage proportional to the current to be measured.
shunt qualifies a machine to denote that it is excited by a winding in parallel to the armature winding
shunt capacitor power capacitor intended to be connected in parallel with a network
NOTE These capacitors are used primarily for power factor correction by reactive power
shunt capacitor device for generating reactive power for voltage control
shunt reactor reactor intended for shunt connection in a network to compensate for capacitive current
shunt reactor device used for absorbing reactive power for voltage control
shunt regulator regulator that prevents overcharging of a battery by shunting the photovoltaic array current to a low-impedance bypass
shutters mechanically operated safety covers for, or on, orifices, to prevent access to live parts of switchgear
shutters movable part incorporated into a socket-outlet arranged to shield at least the live socket-outlet contacts automatically when the plug is withdrawn
simultaneous demand arithmetic or vectorial sum of the kilowatt or kilovolt-ampere demand that is supplied at a group of supply points during the same integration period
single busbar substation substation in which the lines and transformers are connected to one busbar only [IEC]
single earthing switch three-phase switch on one side of a disconnector
single feeder; radial feeder electric line supplied from one end only [IEC]
single home electricity system non-grid supply of electricity that is generated on the premises of a customer and consumed by the same customer
NOTE An example of such a non-grid system is a solar home system.
single-mode fibres optical fibre in which the radiation of only one bound mode can propagate at the wavelength of interest
single supply supply given to a load by one circuit only
114 NRS 000-1:2008
single wire earth return single phase system in which the neutral side of the connected loads is joined to earth. There is usually no continuous conductor between the source and load neutral, and the neutral current flows through electrodes into the mass of the earth.
single wire earth return a.c. electrical distribution network where only one overhead conductor is used to supply a load, and the earth is used as the current return path
single-line diagram system diagram in which the polyphase links are represented by their equivalent single line
single-point (source) earthing earthing of the distributor neutral conductor at the medium-voltage/low-voltage transformer neutral point
site physical points in the electricity supply network, which have been categorized for the purpose of monitoring QOS
skid boards panels that have a smooth clean upper surface that is placed between the butt of the pole and the face of the excavation, to facilitate the erection of the pole
slave device intelligent electronic device (IED) or remote terminal unit (RTU) that operates under the control of a master station
slenderness factor ratio that characterizes the shape of a specific probability distribution curve ( = mean/standard deviation)
small power distribution unit ready-wired distribution box or board with appropriate circuit-breaker protection and socket-outlets, which is suitable for direct connection to a customer’s electricity dispenser or meter
soil resistivity resistance between the opposite faces of a cube of soil having sides of length 1 m. This value is expressed in ohm meter
solid conductor conductor consisting of a single wire
NOTE The solid conductor may be circular or shaped.
solid earthed neutral system system in which at least one neutral point is earthed directly
solid-link component for use in place of a fuse-carrier, to effect a manual disconnection
solid-link assembly assembly that comprises all components that form a complete device intended to isolate equipment or parts of a reticulation system, or both, form the source of supply
solidly earthed neutral system system whose neutral point(s) is (are) earthed directly [IEC]
solid state meter meter that converts voltage and current inputs into signals, via voltage transformers (VTs), current transformers (CTs) and electronic circuits, that drive a stepper motor which in turn drives the rolling register of the meter
115 NRS 000-1:2008
solid-state regulator regulator that uses solid-state switching devices to control the flow of charge to a battery
NOTE The rate of switching is typically at high frequency.
source earthing single-point (source) earthing, which states: the earthing of the distributor neutral conductor at the medium-voltage/low-voltage transformer neutral point
spacer block piece of timber that is used as a spacer between poles and cross-arms in five-pole structures but that is not intended to be used in contact with the ground
special tool non-standard tool that is necessary to carry out maintenance on a disconnector isolator or earthing switch (or both). Such a tool could be for contact-assembly and contact pressure setting, but also for mechanical bearing assembly and disassembly, etc.
specifically trained person telecommunication authority employee, trained in accordance with the requirements of the Occupational Health and Safety Act, 1993 (Act No. 85 of 1993) and those of the telecommunication authority concerned, for work on shared structures specified mechanical load load specified by the manufacturer, which is used for mechanical tests and forms the basis for the selection of insulators
NOTE Specified mechanical load is commonly used in connection with composite insulators.
specified operating range range of values of a single influence quantity which forms part of the rated operating conditions
speed ratio speed ratio of all fuse-link sizes rated at 100 A and below is the ratio between the current that melts the fuse in 0,1 s and the current that melts the fuse in 300 s
speed ratio ratio of the maximum service speed to the rated speed at full field with the motors grouped for maximum speed
spill amount of oil present out of its normal container
NOTE "Normal" refers to a transformer or a drum, etc. (see electrical equipment).
spinning reserve of a system difference between the total available capacity of all generating sets already coupled to the system and their actual loading [IEC]
splicing fusion of the ends of two fibres to create a joint with minimal optical loss
split concentric cable cable having two conductors in a single concentric layer separated from each other by insulating material
split meter; split prepayment meter prepayment meter that consists of a customer interface unit and a measurement unit
NOTE The intention of a split prepayment meter is to allow credit token interaction between the customer and the customer interface unit without allowing access to the mains conductors in order to minimize the possibility of tampering (unauthorized interference).
116 NRS 000-1:2008
split-concentric cable sheathed cable that has a phase core surrounded by two conductors, a neutral conductor and an earth conductor, that, together, form a single concentric layer around the phase core, the two conductors being separated from each other by insulating material
spur feeder feeder to which subscriber's taps or looped system outlets are connected
spur feeder see branch line, which states: an electric line connected to a main line at a point on its route [IEC]
NOTE A branch line which is a final circuit is called a spur.
standard document, established by consensus and approved by a recognized body, that provides, for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context
NOTE Standards should be based on the consolidated results of science, technology and experience and should be aimed at the promotion of optimum community benefits.
standard for live work written instructions for the safe execution of work on apparatus, constituting an extension of these regulations, stating exactly how live work, referred to in these regulations, is to be carried out
standard network capacity maximum capacity that would economically be allowed on a particular network before system reinforcement is required
standard specification South African specification issued in terms of the Standards Act, 1993 (Act 29 of 1993), provided that, until such time as a South African specification has been issued, the latest revision of another appropriate national specification or an appropriate International Electro-technical Commission specification shall be deemed to be the standard specification.
standard supply supply where the design standard is according to the standard accepted by the utility for the particular type of work
standardization revenue monetary value assigned to the results of a standardization activity, estimated from the expected value added derived from application of the result
standard test conditions prescribed range for influence quantities to be used during testing the performance of a measuring instrument
standard test conditions conditions where the irradiance is 1 000 W/m², the temperature of the photovoltaic cell is 25 °C and the air mass is 1,5 (see air mass which states: a numerical value used to give an overall measure of the amount of atmosphere through which solar radiation has to pass. At sea level, when the sun is directly overhead, the air mass is 1,0. When the sun is lower in the sky (some hours from noon, or in winter months), the solar radiation has to cut through more atmosphere and the air mass is then higher than 1,0)
standard voltage phase voltage of 230 V measured between a phase conductor and the neutral conductor, or a line voltage of the square root of 3 multiplied by 230 V measured between phase conductors [Electricity Act, 1987 (Act No. 41 of 1987), regulation R2265]
117 NRS 000-1:2008
standby capacity capacity available to customers to meet the abnormal load requirements above an agreed normal in the event of failure of alternative generation (or start-up)
standby current current drawn by an inverter when no load is connected to the output
NOTE This should be as small as possible to avoid unnecessary discharge of the storage battery.
standby supply supply which can be used when the normal supply becomes unavailable or inadequate [IEC]
static reactive power compensator device used for automatic reactive power control, for compensator voltage control and for balancing the three phases
station power station or a substation
statistical energy (check) metering metering at the substation, feeder or bulk supply level, of the energy supplied to a project or supply group
stay steel wire, rope or rod, working under tension, connecting a point of support to a separate anchor, or connecting two points of the support [IEC]
stay insulator insulator designed to withstand the tension of a stay wire or rope and to insulate the lower portion of the stay from leakage currents, but not from fault currents
stay wire stranded wire portion of a stay
step potential part of the earth electrode potential gradient that can be bridged by a person from foot to foot through the body
step-up substation transformer substation in which the outgoing power from the transformers is at a higher voltage than the incoming power. [605-01-04]
step-down substation transformer substation in which the outgoing power from the transformers is at a lower voltage than the incoming power [IEC]
stop end (insulating cap) insulating device to terminate the unconnected end of an energized cable
stop-end accessory that provides a means of insulating the unconnected end of an energized cable [IEV 461-10-07, modified]
storage and transport conditions extreme conditions which a non-operating measuring instrument can withstand without damage and without degradation of its metrological characteristic when it is subsequently operated under its rated operating conditions [IEC]
118 NRS 000-1:2008
stored-energy operation operation by means of energy stored in the mechanism itself prior to the completion of the operation and sufficient to complete it under predetermined conditions
stored energy operation (of a mechanical switching device) operation that is completed under predetermined conditions by using energy stored in the switching device prior to the completion of the operation.
strain fitting fitting that transfers the tensile load between the supporting conductor and the strain resisting structures of an aerial bundled conductor system
stranded conductor conductor consisting of a number of individual wires, all or some of which generally have a helical form [IEC]
stranded conductor conductor consisting of a number of wires, all or some of which are wound in a helix
structure relations among the elements of a system
structure building or part of an installation or part of a plant, inside of which a lightning protection zone can be established
structure construction of wood, concrete or steel, used in a line to support conductors or cables (or both) and associated accessories and equipment
structure (of an overhead line) construction, of wood, concrete or steel, used in a line to support conductors or cables (or both) and associated accessories and equipment above the ground
structure (of an overhead line) device designed to carry, through insulators, a set of conductors of a line
structure loading vector resultant sum of the loadings incident to the structure including the mass of the conductors, the wind loading, the tension in the conductors and the forces due to staywires
subdivisions situations where a particular piece of land is subdivided thus allowing for more than one utility service connection to be made to the development
substation (of a power system) part of an electrical system, confined to a given area, mainly including ends of transmission or distribution lines, electrical switchgear and controlgear, buildings and transformers. A substation generally includes safety or control devices (for example protection)
NOTE The substation can be qualified according to the designation of the system of which it forms a part. e.g. transmission, distribution substation, 400 kV or 20 kV substation.
substation (of a power system) part of a power system, concentrated in a given place, including mainly the terminations of transmission or distribution lines, switchgear and housing and which may also include transformers. It generally includes facilities necessary for system security and control (e.g. the protective devices) [IEC]
NOTE According to the nature of the system within which the substation is included, a prefix may qualify it.
119 NRS 000-1:2008
Examples: transmission substation (of a transmission system), distribution substation, 400 kV substation, 20 kV substation.
super-clean material material that, once extruded, is free from a) voids larger than 50 µm, and a maximum of 30 voids per 16,4 cm
3 larger than 25 µm,
b) contaminants larger than 125 µm, and a maximum of 10 contaminants per 16,4 cm
3 in the size
range 50 µm to 125 µm (666 contaminants/kg), and c) translucent material larger than 625 µm
supervision activity , performed either manually or automatically, intended to observe the state of an item
supervision function of indicating the status of and of controlling a call, a system or a network
supervision (supervising; supervised) overseeing of the actions of a person or persons to a degree sufficient to prevent any act which could be dangerous or in contravention of these regulations
NOTE For the purposes of these regulations, the authorized person responsible for the supervision of workmen has to execute the level of supervision demanded by the situation.
supervisory remote control and indications of an auto-recloser or a pole-mounted remote terminal unit by means of a telecommunication link
supplementary insulation independent insulation that is applied in addition to the basic insulation, in order to provide protection against electric shock in the event of a failure of the basic insulation
supplier authorized supplier of electricity
NOTE The supplier can also be a supplier of water, gas, or other services.
supplier party supplying electricity to distribution undertakings or to consumers
supplier (of electricity) authority that, in terms of legislation, has the right to supply electricity
NOTE “Electricity supplier” should always be used instead of “supplier”.
supplier; manufacturer person or company from whom equipment, materials or services can be obtained
supply (of electricity) public service provided by a distribution undertaking to any consumer and determined according to technical and commercial criteria such as frequency, voltage, continuity, maximum demand, point of supply, tariffs
NOTE In French, in a restrictive sense, electricity supplied to a consumer, groups of consumers or other utilities (or both).
120 NRS 000-1:2008
supplier utility supplier of electricity authorized by the National Energy Regulator of South Africa NOTE The supplier might also be a supplier of water, gas, or other services.
supply authority utility, which states: a body, licensed by the National Electricity Regulator, that generates, transmits or distributes electricity. Such a body might be the direct licensee, or an agent (subdistributor) of the licensee.
NOTE The preferred term is “electricity supplier”.
supply authority distributor of electrical power which includes Eskom, municipalities and any other similar organization that is licensed to distribute electrical power
supply authority electrical undertaking that is authorized and licensed by the National Electricity Regulator to supply power to consumers in a designated area
supply disconnection interruption of supply over a significantly long period of time, due to the opening of a switching device [IEC]
supply group key revision number attribute of a supply group and that defines the current key revision number for the supply group, and therefore the current vending key value for the supply group (see also key revision number
supply service; line connection branch line from the distribution system to supply a consumer's installation. [IEC]
supply voltage voltage which a distribution undertaking maintains at the consumer's point of supply [IEC]
NOTE If a supply voltage is specified, for instance in the supply contract, then it is called "declared (supply) voltage".
supply voltage voltage, excluding signal voltage, applied to the circuit of an electrode by an external source
support structure device designed to carry, through insulators, conductors of a line
supporting conductor ABC multicore aerial bundled conductor system that is so installed that only the neutral conductor is under tension
surge transient over voltage or transient overcurrent
surge isolation device component such as an isolation transformer, optocoupler or fibre-optic link, the purpose of which is to protect electronic equipment from surges by means of galvanic isolation
surge management device term that is used to include either a surge isolation device or a surge protection device
121 NRS 000-1:2008
surge protective device (SPD) circuit that consists possibly of silicon suppressors, metal oxide varistors and spark gaps (gas gaps), the purpose of which is to limit transient over-voltages and transient over-currents, appearing on cables, to levels that are safe for the electronic equipment connected to those cables
NOTE There are two basic types of SPD:
a) a type I SPD, which is a current diverting device (for example, a spark gap); and
b) a type II SPD, which is a voltage clamping device (for example, a metal-oxide varistor.
susceptibility inability of a device, equipment or system to perform without degradation in the presence of an electromagnetic disturbance. Susceptibility is the lack of immunity [CIGRE] NOTE 1 Voltage ratings are consistent with the IEC's definitions [IEC 61000-3-7] because of the frequent reference to IEC standards in this document. These ratings may differ from those currently used by ESI members and other NRS documents. NOTE 2 CISPR / IEC definition. Where referred to in the context of radio equipment, the traditional IEEE radio frequency bands, i.e. LF (30 kHz - 300 kHz), MF (300 kHz - 3 MHz), HF (3 MHz - 30 MHz), VHF (30 MHz - 300 MHz), and UHF(300 MHz - 3 GHz) are implied. NOTE 3 The ports of interest are shown in figure 1. The enclosure port is the physical boundary of the apparatus (e.g. enclosure). The enclosure port provides for radiated and electrostatic discharge (ESD) energy transfer, whereas the other ports provide for conducted energy transfer.
suspender wire steel, multistranded wire that is used to support a telecommunication cable on an overhead line
suspension fitting fitting that supports a service cable or conductor at intermediate positions between strain fittings
suspension fitting fitting that supports the aerial bundled conductor at intermediate positions between strain fittings
suspension fitting fitting that supports the aerial bundled conductor at intermediate positions between strain fittings
switch component fitted with an actuator and contacts to make and break a connection
switch mechanical switching device capable of making fault current and carrying and breaking load current
switch device for changing the electric connections among its terminals
switch switching device capable of making, carrying and breaking currents under normal circuit conditions which may include specified operating overload conditions and also carrying currents under specified abnormal circuit conditions such as those of short-circuit, for a specified time [IEC]
122 NRS 000-1:2008
switch mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions, which can include specified operating overload conditions, and also carrying for a specified time currents under specified abnormal circuit conditions such as those of short-circuit
NOTE A switch can be capable of making but not of breaking short-circuit currents
switch chamber; switch room chamber or room that contains switchgear
switchboard two or more switch panels with their interconnecting busbars
switchboard general term that covers switching devices and their associated control, measuring, indicating, alarm, protection and regulating equipment, also assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures, intended in principle for use in connection with the generation, transmission, distribution and conversion of electric energy
switchboard part of a manual or manually supervised exchange at which the interconnection of circuits is manually controlled
switch disconnector mechanical switching device which provides, in the open position, an isolating distance in accordance with specified requirements switch disconnector switch that, in the open position, satisfies the isolating requirements specified for a disconnector
switch disconnector switch which, in the open position, satisfies the isolating requirements specified for a disconnector [IEC]
switch disconnector panel switchgear panel complete with a non-withdrawable type switch disconnector or switch-isolator
switch panel apparatus comprising any one circuit of a switchboard, including the busbar and the connection to the cable
switch yard outdoor enclosed area that contains switchgear
switch-fuse switch-fuse combination switch in which one or more poles have a fuse in series in a composite unit
switch-fuse panel switch-fuse combination panel switchgear panel complete with a non-withdrawable switch-fuse combination
123 NRS 000-1:2008
switchgear general term covering switching devices and their combination with associated control, measuring, protective and regulating equipment, also assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures, intended in principle for use in connection with generation, transmission, distribution and conversion of electric energy NOTE When reference is made in this specification to a switchgear panel and a switchboard, the term switchgear is used.
switchgear (indoor) switchgear and controlgear designed solely for installation within a building or other housing, where the switchgear and controlgear are protected against wind, rain, snow, abnormal dirt deposits, abnormal condensation, ice and frost
switchgear (outdoor) switchgear and controlgear suitable for installation in the open air, i.e. capable of withstanding wind, rain, snow, dirt deposits, condensation, ice and frost
symbol element simple figure with a defined meaning, which has to be combined with other figures to form the complete symbol for a device or a concept. machine, series and shunt field windings, bushes and terminals. When symbol elements are combined in this way, their arrangement is not necessarily related to the physical structure of the device symbolized
switchgear and controlgear equipment provided to be connected to an electrical circuit for the purpose of carrying out one or more of the following functions: protection, control, isolation, switching
switchgear and controlgear – metal-enclosed switchgear and controlgear assemblies with an external metal enclosure intended to be earthed, and complete except for external connections
switchgear panel switchgear panel of modular design that comprises a mechanical switching device (e.g. a circuit-breaker, a switch, a switch-disconnector or a switch-fuse) and its associated control, measuring, indicating, alarm, protection and regulating equipment with interconnections, accessories, enclosures and support structure
switching opening or closing of circuit-breakers or switches on links in a system
switching opening or closing of circuit-breakers or switches
switching process of temporarily associated functional units, transmission channels or telecommunication circuits for the purpose of providing a desired telecommunications facility
switching differential ratio of the measured switch-on level to the measured switch-off level
124 NRS 000-1:2008
switching substation substation which includes switchgear and usually busbars, but no power transformers [IEC]
switching unit aggregate of switching equipment and auxiliary equipment at a node in a telecommunication network enabling connections, as required by individual users to be established
switching unit of a photo-electric control unit (PECU) part of a two-part PECU that contains the load-switching device
switch yard outdoor enclosed area that contains switchgear
symmetrical fault insulation fault at one point of a circuit, affecting the insulation of all three phase conductors between one another and usually to earth
synchronization process of adjusting clock frequencies to achieve synchronism of two time-varying, phenomena, time-scales or signals
synchronization The matching of two systems with respect to their frequency and to their voltage magnitude and voltage phase for interconnection purposes [IEC]
synchronization of two systems matching of two systems with respect to their frequency and to their voltage magnitude and voltage phase for interconnection purposes
synchronous condenser synchronous machine used for reactive power control
synchronous operation of a machine ideal operating condition of a synchronous machine connected to the network in which the electrical angular velocity of the machine corresponds with the network frequency
NOTE Under practical operating conditions the angular velocity of the machine may slightly oscillate around the ideal value.
synchronous operation of a system condition of a system in which all machines are in synchronous operation
system set of interrelated elements considered in a defined context as a whole and separated from their environment
NOTE 1 A system is generally defined with the view of achieving a given objective, e.g. by performing a definite function.
NOTE 2 Elements of a system may be natural or man-made material objects, as well as modes of thinking and the results thereof (e.g. forms of organization, mathematical methods, programming, languages)
NOTE 3 The system is considered to be separated from the environment and the other external systems by an imaginary surface, which cuts the links between them and the system.
NOTE 4 The term "system" should be qualified when it is not clear from the context to what it refers, e.g. control system, colorimetric system, system of units, transmission system.
125 NRS 000-1:2008
system electrical system in which all the conductors and devices are electrically connected to a common source of electrical energy
system configuration permanent or temporary grouping of similar or dissimilar individual system patterns
system configuration specified arrangement of telecontrol stations and their interconnections
system demand control control of the power demand of the consumers on a power system [IEC]
system diagram topological representation of a system in which the information content depends on a specific requirement [IEC]
system earthing – effective
earthed system, or portion of the system, in which the power frequency phase-to-earth over voltages associated with earth faults are limited to 0,8Um
system earthing - non-effective system in which the neutral is intentionally connected to the system earth through a current limiting device
system master station centrally located unit that collects, stores and processes data from, and transmits data to, credit dispensing units (CDUs) and distributors’ management computer systems
NOTE 1 A system master station is capable of producing, from the data collected, reports and information as defined from time to time by the supply authority.
NOTE 2 A system master station is also capable of transmitting processed data and control information to and from a supply authority’s computer systems.
system operational diagram system diagram representing a particular operational condition
system pattern repetitive arrangement of the nodes in a system and their connections, e.g. feeder, ring, mesh. etc.
system-minutes unit used to measure the relative loss of supply in an electricity supply network
SZ method of constructing a cable where the direction of rotation of the elements of the cable reverses periodically along the cable take-over act of taking over equipment by the purchaser to operate, after it has been accepted and approved, with or without reservations
NOTE The date of take-over is often associated with the commencement of a guarantee period.
126 NRS 000-1:2008
take-over current current co-ordinate of the intersection between the time-current characteristics of two overcurrent protective devices
tampering unauthorized interference with the supplier’s equipment, or removal of the supplier’s seal from a protective device or from metering equipment tampering unauthorized interference with the supplier's equipment, or the removal of the supplier's seals from the protective devices or metering equipment, or the illegal connection of cables to the utilities’ infrastructure tamper detection means of detecting whether unauthorized individuals have accessed the meter tapped (tee off) substation single supply substation fed from a single branch line [IEC
tariff statement setting out the components to be taken into account and the methods to be employed in calculating the amounts to be paid to the supply undertaking by the consumer, according to the characteristics of the supply
tariff price structure for electricity supplied to a point of supply
tariff combination of monthly charges each at particular rates that are usually escalated annually and is applied to recover measured quantities such as consumption and capacity costs and unmeasured quantities such as service costs
tariff capital allowance contribution to network capital costs that are contained in the tariffs
tariff charges charges that make up the tariff
tariff module device installed at a metering point, and which is capable of receiving inputs from meters, accumulating these values separately for various user defined rate periods and seasons, storing these totals in memory, and displaying the stored totals
tariff rates level at which each of the tariff charges are set
taxes contributions required by the utility, which are in addition to costs incurred directly for the provision of electrical energy and services, such as contributions to rates, shareholders dividends, return-on-investments, taxes required by the National Electricity Regulator and street lighting, but excluding working capital and development capital used for future system reinforcement and upgrading
technical loss factor factor which links energy sales, energy delivered and technical losses
NOTE technical loss factor multiplied by energy sales equals energy delivered.
127 NRS 000-1:2008
technical losses energy losses in electricity supply networks due to the resistivity of the conductors and energization of transformers
NOTE This is generally referred to as copper and iron losses. Technical losses can be calculated using well proven methods that yield acceptable accuracy levels.
technical losses losses incurred over electrical networks due to the characteristics of the physical equipment usually associated with dissipation
tee-connector pre-moulded connector for connection to a bushing in conjunction with an elbow connector to permit termination of a second cable core to a bushing
teed feeder main line to which branch lines are connected [601-02-11]
teed line main line to which branch lines are connected
teed system modified radial system to which spurs have been added [601-02-16] TN-C-S system neutral and protective functions combined in a single conductor between the source and the point of supply and separated in a consumer’s installation
NOTE The usual form of a TN-C-S system is as shown, where the supply is TN-C and the arrangement in the consumer’s installation is TN-C-S.
All exposed conductive parts of a consumer’s installation are connected to the PEN conductor through the consumer’s earth terminal and the neutral terminal, these terminals being permanently connected together.
POINT OF SUPPLY
CONSUMERS EARTH
TERMINAL
CONSUMERS PREMISES
EXPOSED CONDUCTIVE
CONSUMERS EARTH
TERMINAL
SOURCE OF ENERGY
SOURCE
EARTH
COMBINED PROTECTIVE EARTH
AND NEUTRAL (PEN) CONDUCTOR
L1
L2
L3
N
(PE)
L1 L2 L3 N NL
CIRCUIT-BREAKER
AND METERING
128 NRS 000-1:2008
TN-S system separate neutral and protective conductors throughout the system.
NOTE The protective conductor (PE), which is connected to the source neutral earth, is either a separate conductor or the metallic covering of the cable that supplies the installations.
All exposed conductive parts of a consumer’s installation are connected to this protective conductor via the consumer’s earth terminal.
telecommunication authority provider of a telecommunication service network, which includes Telkom and any other similar organization that is licensed to provide a telecommunication service network
telecommunication authority licensed provider(s) of a telecommunication service NOTE Telecommunication authorities include Telkom and any other similar organizations that are licensed to provide a telecommunication service.
telecommunications authority (review SNO)
authority responsible for administering the Regulations of the Post Office Act, 1958 (Act 44 of 1958)
telecommunication line apparatus, instrument, wire, optical fibre, pipe, pneumatic or other tube, which may be used for, or in connection with, the sending, conveying, transmitting or receiving of signs, signals, sounds or other information, but excluding telecommunication poles or masts
templating activity of placing or positioning the structure on the ground profile, drawing or map
temporary earth; working earth supplementary earthing device that is applied at, or within view of, the work site and that is removed before clearance of the permit to work
temporary over-voltage oscillatory phase-to-earth or phase-to-phase over voltage at a given location in a system, of relatively long duration and that is undamped or only weakly damped
NOTE Temporary over-voltages usually originate from switching operations or faults (e.g. load rejection, single phase faults) or from non-linearities (ferro-resonance effects, harmonics). They may be characterized by their amplitude, their oscillation frequencies, and by their total duration or their decrement. [IEC]
POINT OF SUPPLY
CONSUMERS EARTH
TERMINAL
CONSUMERS PREMISES
EXPOSED CONDUCTIVE
PARTS
(eg. appliances)
CONSUMERS EARTH
TERMINAL
SOURCE OF ENERGY
SOURCE
EARTH
L1
L2
L3
N
(PE)
L1 L2 L3 N NLE
CIRCUIT-BREAKER
AND METERING
PROTECTIVE CONDUCTOR
129 NRS 000-1:2008
temporary over-voltage power-frequency over voltage of relatively long duration [IEC]
NOTE The over voltage can be undamped or weakly damped. In some cases, its frequency can be several times lower or higher than the power frequency.
temporary supply electricity supply that is provided to a customer in the event of unusual circumstances. Such a supply might not conform to the service levels normally provided by agreement between the customer and the licensee
temporary supplies supplies to customers that are limited in such as a building supply or for a function or such
ten (10) minute r.m.s. value average (root mean square) value of all the samples taken during a 10 min period
tensile load tensile load applied during testing, and at which the cable breaks or becomes permanently deformed
terminal assembly two or more terminals fixed to the same conductive part
terminal block support made of insulating material on which all or some of the terminals of the meter are grouped together
terminal block assembly of terminals in a housing or body of insulating material to facilitate interconnection between multiple conductors
terminal block insulating part carrying one or more mutually insulated terminal assemblies and intended to be fixed to a support
terminal box box, usually covered, mounted on the machine or separately and containing terminals which make the connections between the machine and the supply cables
terminal box air-filled or compound-filled box that fully encloses a termination [IEV 461-10-03, modified]
terminal box box enclosing a cable termination and forming a part thereof
terminal cover cover which protects the meter terminals and, generally, the ends of the external wires or cables connected to the terminals
terminal cover cover, enclosing the meter terminals and, generally, the ends of the external wires or cables that are connected to the terminals [IEC]
termination device fitted to the end of a cable to ensure electrical connection with other parts of the system and to maintain the insulation up to the point of connection [IEV 461-10-01]
termination arrangement provided for making the connections between the machine internal leads and the external conductors
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termination part of an accessory to which a conductor is permanently attached
termination tail part of a cable termination that, for an impregnated-paper insulated cable, extends from the metallic sheath to the end of the core insulation and, in the case of an cross linked polyethylene (XLPE) insulated cable, extends from the extruded bedding to the end of the core insulation
test technical operation that consists of the determination of one or more characteristics of a given product, process or service according to a specified procedure
NOTE A test is carried out to measure or classify a characteristic or a property of an item by applying to the item a set of environmental and operating conditions and/or requirements.
test block device that permits access to voltage and current circuits for testing purposes while the metering installation is in normal service
test current current that is specified by the manufacturer for the main adjustment of the meter (full load adjustments)
test facility device connected to the metering circuit that allows for the connection of a test instrument to measure burden, current or voltage
NOTE Such devices could be test blocks.
test laboratory facility that is used for the testing and calibration of meters and metering installations not necessarily approved/accredited by the NER/SANAS
test method specified technical procedure for performing a test
test position (of a withdrawable part) position of a withdrawable part in which an isolating distance or segregation is established in the main circuit, and in which the auxiliaries are connected
test report document that presents test results and other information relevant to a test
testing laboratory laboratory that performs tests
NOTE Not necessarily accredited by SANAS.
touch potential part of the earth electrode potential gradient that can be bridged by person from hand (or hands) in contact with a structure, through the body to the feet or other earthed point
TASE.2 TASE based on the ICCP model
theft unauthorized use of electricity owing to tampering
thermal runaway (battery) critical condition arising during constant voltage charging in which the current and the temperature of the battery produce a cumulative mutually-reinforcing effect which further increases them and can lead to the destruction of the battery
131 NRS 000-1:2008
thermal runaway of an arrester term “thermal runaway” is used to describe a situation when the sustained power loss of an arrester exceeds the thermal dissipation capability of the housing and connections, leading to a cumulative increase in the temperature of the resistor elements and culminating in failure [IEC]
thermal stability of an arrester arrester is thermally stable if, after an operating duty causing temperature rise, the temperature of the resistor elements decreases with time, when the arrester is energized as specific continuous operating voltage and at specified ambient conditions
thimble component designed to protect a stay wire or rope against abrasion and excessive bending at a
third party supplies/wheeling situations where electricity is supplied by a particular supplier over the network of another to a customer
thixotropic gel gel that undergoes a reduction in viscosity when shaken, stirred or otherwise mechanically disturbed and that readily exhibits a stable form at rest three-phase system diagram diagram of a three-phase system in which all phase and neutral conductors are each represented by separate lines [IEC]
through connector see ferrule, which states: connector for connecting two consecutive lengths of conductor [IEC]
through connector metallic device for connecting two consecutive lengths of conductor
tie clamp part of a cable tie that binds together its ends round the cables that it ties
time of use concept referring to the time when a specific product or service is utilized. It is applied to tariffs where the price of the product or service varies with time
time of use metering ability to record consumption according to time-dependant tariffs
to earth/to ground effect the necessary connections in order to maintain a given point of equipment, an installation or a system as close as practical to earth potential
to earth/to ground (USA) (equipment, an installation or a system); effect the necessary connections in order to maintain a given point of equipment, an installation or a system as close as practicable to earth potential [IEC]
toggled control single latching switch that enables a single control operation in one position and disables the same control operation in the other position
token element that is used to transfer encrypted information between a credit dispensing unit (CDU) and an electricity dispenser (ED)
NOTE 1 The information consists of credit information, instructions and any other information to be passed between the CDU and the ED.
NOTE 2 A group token is a token that will be accepted by any one of a predefined group of EDs.
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NOTE 3 An engineering token is a token used to initiate or perform specific engineering or management functions on an ED. Only installation or maintenance personnel normally use these tokens. A coding token is a particular type of engineering token used to set the ED key.
NOTE 4 A unique token will only be accepted by the dispenser for which it was issued.
NOTE 5 A token can act as a receipt.
token encryption device security module: physically and logically secure device which performs all tasks that have a security requirement, for example, token encryption, credit control, password control, message authentication and verification
NOTE A security module can serve several CDUs.
token identifier value associated with a token and that distinguishes the token from other tokens issued for the
same electricity dispenser − it is derived from the date and time the token is issued at the credit dispenser
total consumption integrated electrical consumption from a specified time until the register is reset total distribution losses difference between total distribution purchases and total distribution sales total harmonic distortion see voltage harmonics
total harmonic distortion total harmonic factor at the output of a transmission channel or two-part device producing harmonic distortion, when the input signal is a sinusoidal oscillation of a specified frequency and amplitude
total harmonic distortion ratio of the r.m.s. value of the harmonic content to the r.m.s. value of the fundamental component or the reference fundamental component of an alternating component
NOTE 1 The total harmonic ratio depends on the choice of the fundamental component. If it is not clear from the context which one is to used an indication should be given.
NOTE 2 The total harmonic ratio may be restricted to a certain harmonic order. This is to be stated.
total sales total measured or estimated energy consumption of a group of customers
totalization operation of adding the energy usage from each feeder to a particular customer to obtain the total energy usage for that customer. See distributor which states: an entity which provides a physical supply (of electricity) to a customer on behalf of a supplier and that is contracted to do so through a connection agreement with that customer [IEC]
touch voltage voltage that, during a fault, appears between simultaneously accessible conductive parts
touch voltage voltage appearing during an insulation fault, between simultaneously accessible parts
NOTE 1 By convention, this term is used only in connection with protection against indirect contacts.
NOTE 2 In certain cases, the value of the touch voltage may be appreciably influenced by the impedance of the person in contact with these parts.
133 NRS 000-1:2008
township any land laid out, divided into or developed as a site for residential, business, industrial or similar purposes, where such a site is arranged in such a manner as to be intersected or connected by or to abut on any street NOTE The site or street should, for the purposes of this definition, include a right of way or any site or street which has not been surveyed or which is only notional in character.
traceability property of the result of a measurement or of a value of a standard such that it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties [IEC]
NOTE 1 The concept is often expressed by the adjective traceable.
NOTE 2 The unbroken chain of comparisons is called a traceability chain.
traceability process whereby the indication of a measuring instrument can be compared, in one or more stages, with a national standard for the measurand in question
tracking progressive degradation of the surface of a solid insulating material by local discharges to form conducting or partially conducting paths
NOTE Tracking usually occurs due to surface contamination.
tracking progressive formation of conducting paths on the surface of a solid insulating material, and caused by the combined effects of electric stress and electrolytic contamination on this surface
traction substation substation, the main function of which is to supply a traction system
trainee authorized person person who has been authorized in writing to carry out switching, isolating, testing and earthing procedures on defined apparatus or equipment under the instruction of the controller, and under direct supervision of an authorized person
transfer bus coupler circuit-breaker used either for connecting two sets of busbars or for putting a feeder on transfer
transfer circuit-breaker circuit-breaker used to energize the transfer busbar when putting a feeder on transfer
NOTE A transfer busbar is sometimes provided at EHV substation. It is a busbar in addition to the normal substation busbars, to which feeders can be connected temporarily, usually for the purpose of maintenance. The operation required to connect a feeder to the transfer busbar is known as “putting a feeder on transfer”.
transformation of electricity transfer of electricity through a power transformer [IEC]
transformer static item of apparatus used to transform or regulate voltage, including all conductors permanently connected to its terminals
transformer electric energy converter without moving parts that changes voltages and currents associated with electric energy without change of frequency
134 NRS 000-1:2008
transformer circuit –breaker substation, one of the circuit-breakers located on each side of the transformer and which is usually designated
transformer substation substation at which the electric energy of a primary supply system is transformed to the voltage of the contact line
transformer substation substation containing power transformers interconnecting two or more networks of different voltages [IEC]
transient fault insulation fault which only temporarily affects a device's dielectric properties which are restored after a short time [IEC]
transient over-current current that flows as a result of a transient over-voltage
transient over-voltage short duration over voltage of a few milliseconds or less, oscillatory or non-oscillatory, usually highly damped [IEC]
transient over-voltage temporary, superimposed voltage that is induced onto power cables and onto signal cables owing to switching, lightning and electrostatic discharge events
NOTE The duration of transient over voltage is usually less than 1 ms.
transient over-voltage short-duration over-voltage of a few milliseconds (ms) or less, oscillatory or non-oscillatory, usually highly damped
NOTE 1 Transient over voltages may be immediately followed by temporary over-voltages. In such cases the two over-voltages are considered as separate events.
NOTE 2 IEC defined three types of transient over voltages, namely slow-front over voltages, fast-front over voltages and very fast-front over voltages according to their time of peak, tail or total duration, and possible superimposed oscillations.
transient suppression device surge protection device (SPD), which states: A circuit that consists possibly of silicon suppressors, metal oxide varistors (MOVs) and spark gaps (gas gaps), the purpose of which is to limit transient over voltages and transient over currents, appearing on cables, to levels that are safe for the electronic equipment connected to those cables
NOTE There are two basic types of SPD:
a) a type I SPD, which is a current diverting device (for example, a spark gap); and
b) a type 2 SPD, which is a voltage clamping device (for example, a metal-oxide varistor (MOV).
transition joint straight or branch joint that forms a connection between cables having different types of insulation
transition joint accessory making a connection between two cables having different types of insulation
transmission line means for conveying electromagnetic energy between two points with a minimum of radiation
transmission line line which is part of an electric power transmission system
135 NRS 000-1:2008
transmission line overhead power line to transfer large amounts of electrical energy
transmission line manufactured transmission medium used to convey electromagnetic energy between two points with a minimum of radiation
transmission of electricity transfer in bulk of electricity, from generating stations to areas of consumption [IEC]
transmission system medium voltage, high voltage, extra-high voltage or ultra-high voltage apparatus installed for the transmission and transformation of electrical energy, including the switchboards at major substations
transmission system
1). set of principles defining a particular method of transmission.
2) whole of the means of transmission between two points, comprising the transmission medium, terminal equipment, any necessary intermediate equipment and any equipment provided for such ancillary purposes as power feeding, supervision and testing.
treated/treatment impregnated/impregnation with an acceptable preservative
tree'd system modified radial system to which spurs have been added
trip-free facility facility on a mechanical switching device, such that the contacts close fully, then return to and remain in the open position when the closing operation is initiated after the initiation of the trip operation, even if the closing command is maintained
trip-free mechanical switching device mechanical switching device, the moving contacts of which return to and remain in the open position when the opening operation is initiated after the initiation of the closing operation, even if the closing command is maintained
NOTE To ensure proper breaking of the current which may have been established, it may be necessary that the contacts momentarily reach the closed position.
triple busbar substation substation in which the lines and transformers are connected via three busbars by means of selectors [IEC]
twinning process of twisting two insulated conductors (cores) together to form a pair
twinning (line pairing) imperfect interlacing of the scanning lines
type test conformity test made on one or more items representative of the production
type test test that is required to be carried out on equipment to prove that the equipment complies with certain specifications applicable to its acceptability for the purpose for which it was intended
136 NRS 000-1:2008
type test test that is conducted before a type of cable covered by this specification is supplied on a general commercial basis, in order to demonstrate that the cable has the necessary performance characteristics for the intended application. The test is of such a nature that, after it has been successfully completed, it need not be repeated unless changes that might change the performance characteristics of the cable are made in the cable materials, or in the design or in the method of manufacture
type test test made before supplying, on a general commercial basis, a type of cable covered by this standard in order to demonstrate satisfactory performance characteristics to meet the intended application. The test is of such a nature that, after it has been successfully completed, it need not be repeated unless changes are made in the cable materials or design or manufacturing process that might change the performance characteristics
type test test carried out at the introduction of a new material or component (or both)
type test test of one or more samples of equipment (or parts of equipment) made to a particular design, to show that the design and construction meet one or more requirements
type testing compliance testing on the basis of one or more specimens of a product representative of their production [ISO/IEC Guide 2] type tests tests required to prove the adequacy of the design
ultimate tensile strength highest load applied to a metal in the course of a tensile test, divided by the original cross-sectional area
ultra-high voltage set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range Un > 400 kV
ultraviolet-stabilized modified by methods such as carbon loading to withstand ultraviolet radiation
unarmoured cable cable that contains no metallic armouring elements uncertainty parameter that is associated with the result of a measurement which characterizes the dispersion of the values that could reasonably be attributed to the quantity being measured
undercut peripheral portion of an excavation which is undercut to ensure that the stay anchor assembly bears against undisturbed soil [IEC]
underground cable electric line with insulated conductors buried directly in the ground, or laid in cable ducts, pipes, troughs, etc.
NOTE The same expression is used to describe the item physically.
underground cable electrical work arrangement of grouped single core or multicore electrical cables or telecommunication cables (or both) and joints buried at various depths below ground level and separated at various distances (where more than one cable is involved)
137 NRS 000-1:2008
underground cable; cable electric line with insulated conductors buried directly in the ground, or laid in cable ducts, pipes, troughs, etc [IEC]
NOTE The same expression is used to describe the item physically.
underground system system consisting essentially of underground cables [IEC]
under voltage event reduction in the supply voltage to a value less than 90 % of the dip threshold voltage for a period of time exceeding 3 s, and which is not an interruption
unfilled enclosure metallic enclosure designed for the purpose of receiving and protecting the end(s) of cable(s) in air
NOTE It follows that such an enclosure can be self-contained and removable; it can also be a compartment of the connected equipment and therefore an integral feature of that equipment; it can also be a stand-alone item of equipment, for example a junction box.
unique group See unique supply group
unique supply group supply group that associates a set of electricity dispensers on a geographical or a regional basis, in which each and every electricity dispenser in the supply group has a unique dispenser key
uni-strut proprietary support channel for cables
unit (of an arrester) completely housed part of an arrester which can be connected in series and/or in parallel with other units to construct an arrester of higher voltage and/or current rating [IEC]
NOTE A unit of an arrester is not necessarily a section of an arrester.
unit auxiliaries auxiliary equipment specific to the unit and indispensable for its operation, e.g. mills, circulating pumps, induced draught fans
unit generator transformer transformer connected to the generator terminals through which output power of the generating set is transmitted to the system
unit protection
protection whose operation and section selectively are dependent on the comparison of electrical quantities at each end of the protected section
unit protection
apparatus that is able to detect a fault in a predefined section of the power system and that under fault conditions causes one or more circuit-breakers to disconnect the faulty section
unitary design compartments and transformer provided in a "unitary" design are constructed to make up a non-dismountable whole, i.e. a unit that is not intended to be disassembled in the field to allow removal of the compartments or the transformer
unmanned substation substation which is operated by personnel who are not stationed at the substation [IEC]
138 NRS 000-1:2008
unplanned interruption interruption that occurs when a component is taken out of service immediately, either automatically or as soon as switching operations can be performed, as a direct result of emergency conditions, or an interruption that is caused by improper operation of equipment or human error
unplanned interruption on EHV and HV networks a) momentary interruption
unplanned interruption in the range > 3 s to ≤ 1 min b) sustained interruption unplanned interruption with a duration exceeding 1 min NOTE 1 In general a one minute limit differentiates all automatic reclose events from events involving operator intervention. A one minute classification is commonly used internationally by transmission utilities. NOTE 2 In some cases, transmission utilities may use a ≤ 10 s subclassification to cover three-phase auto-recloser events not related to generation supply points (the latter may have dead times of 20 s to 30 s and restoration times of up to 45 s). unplanned interruption on MV and LV networks a) momentary interruption
unplanned interruption in the range > 3 s to ≤ 5 min b) momentary interruption event where an interrupting device has a sequence of operations, and then holds, the momentary interruptions are considered one momentary interruption event NOTE 1 Examples of such devices are reclosers or breakers that operate two, three or four times and then hold. NOTE 2 The sequence of events is completed in a specified time not exceeding 5 min.
c) sustained interruption
unplanned interruption with a duration exceeding 5 min unscreened (insulation) insulation that does not have a earthed metallic layer
unscreened separable connector separable connector which does not have a screened external surface
unscreened separable connector separable connector that does not have an external screen. unscreened separable connector termination air insulated termination that is fitted with unscreened separable connectors
upper contact source-side spring-loaded contact of a cut-out base
139 NRS 000-1:2008
urban networks serving formally or informally built structures, usually of high density, serviced by well established infrastructure
urban descriptive of an area that has formally or informally built structures, usually of high density, served by a well-established infrastructure (roads, telecommunication networks, etc.). The power network is usually supplied by more than one distribution station.
urban formally or informally built structures, usually of high density, served by a well established infrastructure (roads, telecommunications, etc.). The power network is usually supplied by more than one distribution station.
urban (areas) areas characterized by formally or informally built structures, usually of high density, served by well established infrastructure (roads, telecommunications, etc.). The power network is usually supplied by more than one distribution station.
urban networks supply to an applicant will be considered to be urban when any one of the following conditions are met:
a) When it is proclaimed a township or within a proclaimed township as determined by the townships board;
b) When the number of connections within 1 km radius of the particular point of supply exceeds 314. All connections within the particular development will then qualify;
c) When the number of, current and newly applied connections per km of MV line exceeds 44 and there must be at least 40 connections in one development; and
d) Contestability (of work). A customer has the right to contest a quote by the utility and thus use a contractor to do the work.
(of supply) Where a customer does not have to be supplied with energy and customer services by the utility to whose network it is connected.
urge management device term that is used to include either a surge isolation device (SID) or a surge protection device (SPD)
users organizations that purchase, operate and maintain equipment
utility organization such as a municipality or Eskom Distribution that supplies electrical energy using its own infrastructure, to customers within its licensed area of supply
utility; licensee body, licensed by the National Electricity Regulator, that generates, transmits or distributes electricity. Such a body might be the direct licensee, or an agent (sub-distributor) of the licensee.
utilized customer capacity maximum capacity used by the customer at the specific location of the customer
validation process of checking the data integrity of a message, or selected parts of a message
valid test certificate certificate copy of the original test certificate of a test conducted by an approved testing authority
140 NRS 000-1:2008
var-hour meter (reactive energy meter) instrument intended to measure reactive energy by integrating reactive power with respect to time.
var hour meter (reactive energy meter) electricity meter that measures and registers the integral, with respect to time , of the reactive power of the circuit in which it is connected
NOTE The unit in which this integral is measured is usually the kilovar-hour varistor resistor whose resistance is dependent on voltage
vectorial simultaneous demand sum of demands for a group of supply points, calculated according to the following formulae:
( ) ( )
∑∑∑
=
+=
kW, kW
and ,kvar kW kVA 22
where the sum of kW and kvar is for one group of supply points for each integrating period.
verification execution of specified tests to measure the ability of a process or a person to meet specified criteria
verification (of calibration) operations which is used to check whether the indications, under specified conditions, correspond with a given set of known measurands within the limits of a predetermined calibration diagram
NOTE 1 This term is used in the “ uncertainty” approach.
NOTE 2 The known uncertainty of the measurand used for verification will generally be negligible with respect to the uncertainty assigned to the instrument in the calibration diagram.
vertical personal reach vertical distance from a person’s feet to the tip of the fingers of an upward stretched hand viscosity ability of a certain volume of oil to flow over a period of time at a given temperature
NOTE The viscosity properties are directly related to the cooling characteristics of the oil.
visual display unit unit comprising devices which are necessary to display information required and, possibly to include an acknowledgement facility [IEC]
voltage (V) difference in electrical potential between any two conductors or between a conductor and earth
voltage circuit (general) circuit of a measuring instrument to which is applied the voltage of the circuit to which the measuring instrument is connected.
NOTE This voltage can be:
a) the voltage directly involved in the measurement,
b) a proportional voltage supplied by an external voltage transformer or voltage divider; or
c) derived by means of an external series resistor or impedance.
141 NRS 000-1:2008
voltage circuit; shunt circuit internal connections of the meter, part of the measuring element and power supply for the meter, supplied with the voltage of the circuit to which the meter is connected [IEC]
voltage control adjustment of the network voltages to values within a given range
voltage deviation difference, generally expressed as a percentage, between the voltage at a given instant at a point in the system, and a reference voltage such as: nominal voltage, a mean value of the operating voltage, declared supply voltage
voltage dip sudden reduction in the r.m.s. voltage, for a period of between 20 ms and 3 s, of any or all of the phase voltages of a single-phase or a polyphase supply. NOTE 1 The duration of a voltage dip is the time measured from the moment the r.m.s. voltage drops below 0,9 per unit of declared voltage to when the voltage rises above 0,9 per unit of declared voltage
NOTE 2 The definition of a voltage dip in SANS 61000-4-30 is more generic, as the duration of a voltage dip is not internationally agreed. The above definition is applicable for the assessment and classification of dips as specified in NRS 048-2.
voltage drop probability level (p) probability (p.u. or percentage) that, at the design load, the voltage drop measured at the point of supply, for a customer connected at the end of the heaviest loaded circuit of the system under consideration, will be within the required voltage drop limit
NOTE 1 The opposite of voltage drop probability level is voltage drop risk level.
NOTE 2 The designer’s choice of the voltage drop probability level will be influenced by his confidence that the load will have the characteristics of the chosen beta distribution function.
voltage drop risk level see voltage drop probability level, which states: probability (p.u. or percentage) that, at the design load, the voltage drop measured at the point of supply, for a customer connected at the end of the heaviest loaded circuit of the system under consideration, will be within the required voltage drop limit
NOTE 1 The opposite of voltage drop probability level is voltage drop risk level.
NOTE 2 The designer’s choice of the voltage drop probability level will be influenced by his confidence that the load will have the characteristics of the chosen beta distribution function.
voltage flicker modulation of the amplitude of the supply voltage, perceived by the observer as a fluctuation of light intensity in electric lighting. levels. NOTE 1 The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points. NOTE The above definition is commonly used to refer to the QOS parameter that gives rise to flicker. SANS 61000-4-30 more fundamentally defines “flicker” as the “impression of unsteadiness of visual sensation by a light stimulus whose luminance or spectral distribution fluctuates with time.” voltage harmonics sinusoidal components of the fundamental waveform (i.e. 50 Hz) that have a frequency that is an integral multiple of the fundamental frequency
142 NRS 000-1:2008
NOTE
— Odd harmonics are defined as the 3rd (150 Hz), 5th (250 Hz), etc.
— Even harmonics are defined as the 2nd (100 Hz), 4th (200 Hz), etc.
— Interharmonics are frequency components that are not an integral multiple of the fundamental frequency
— Total harmonic distortion (THD) is given by:
THD = ∑=
Vh
2
h 1
N
where
Vh is the per cent r.m.s. value of the hth harmonic or interharmonic voltage component,
and N is the highest harmonic considered in the calculation.
voltage level nominal voltage values used in a given system [IEC]
voltage monitoring/alarming facility facility that monitors the measuring of voltage on the secondary part of the VT without circuit intrusion
voltage regulation ability of the steady state r.m.s. voltage to remain between the upper and lower limits
voltage regulation control of design parameters or equipment, to maintain the voltage deviation at specified points within certain limits
voltage regulation percentage change to the output voltage of a device when a load is applied to the output and based on the voltage before the load was applied
voltage regulation ability of the steady-state r.m.s. voltage to remain between the upper and lower limits NOTE The assessment criteria require both the measurement instrument to be defined, and a statistical criterion to be applied to the measured data points
voltage regulation concept of managing the voltage drop profile from a regulated busbar (MV of transformer with OLTC) down to the customers supply point so that the supply voltage is maintained within
statutory or contracted voltage limits (generally 230V ± 6 %)
voltage regulator device used for automatic voltage control at a pre-set voltage
voltage transformer VT instrument transformer in which the secondary voltage, in normal conditions of use, is substantially proportional to the primary voltage, and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections [IEC]
voltage unbalance condition in a polyphase system in which the r.m.s. values of the line (phase) voltages (fundamental component) or the phase angles between consecutive line voltages, are not all equal [SANS 61000-4-30]
143 NRS 000-1:2008
NOTE The unbalanced voltages can be represented by the sum of three sets of symmetrical vectors, i.e.:
a) the positive sequence set, consisting of three vectors all equal in magnitude and symmetrically spaced, at 120° intervals, in time-phase, their phase order being equal to the phase order of the system-generated voltages,
b) the negative sequence set, consisting of three vectors all equal in magnitude and symmetrically spaced, at 120° intervals, in time-phase, their phase order being the reverse of the positive sequence phase order, and
c) the zero sequence set, consisting of three vectors, all equal in magnitude and phase.
Voltage unbalance (UB) is usually expressed as a percentage, given by:
100 ×=
pVnVUB
where
Vn is the negative sequence voltage, in volts; and
Vp is the positive sequence voltage, in volts.
Alternatively, simultaneous measurement of the three r.m.s. line-to-line voltages can be used to calculate unbalance:
100 6β31
6β31×
−+
−−=UB
where
( )2231
223
212
431
423
412
VVV
VVβ
V
++
++=
and where, for example,
V12 represents the fundamental frequency, line-to-line voltage between phases 1 and 2.
voltage unbalance polyphase system, a condition in which the r.m.s. values of the phase voltages or the phase angles between consecutive phases are not all equal
voltage unbalance phenomenon due to the differences between voltage deviations on the various phase, at a point of polyphase system, resulting from differences between the phase currents or geometrical asymmetry in the line
voltage unbalance voltage unbalance arises in a polyphase system when the magnitudes of the phase voltages or the relative phase displacements of the phases (or both) are not equal
warning notice portable notice provided to indicate that work is in progress on a supply system or apparatus or to indicate any special operating conditions in force on any panel or circuit, or to indicate both.
144 NRS 000-1:2008
wayleave agreement right of way obtained from a land owner, who signs an agreement with the supply authority, for the installation, operation and maintenance of a power system
NOTE It is not registered against the title of the property.
watt-hour meter active energy meter instrument that is intended to measure active energy by integrating active power with respect to time [IEV 301-04-17]
watt-peak power (of a photovoltaic (PV) module) maximum power, in watts, that a photovoltaic module can deliver under standard test conditions
weak link (in the context of ABC fittings fitting that can be fitted between the pole fitting and a suspension fitting and that is designed to fail at a predetermined load, generally less than the breaking force of the aerial bundled conductor or of the suspension fitting
weather stabilized modified by methods such as carbon loading to withstand ultraviolet radiation and the effects of temperature, humidity and wind
weighting method of assigning weights to different categories for use in allocation methods. Usually aimed at expressing costs or number of customers relative to each other
wet power-frequency withstand voltage power-frequency voltage which the insulator withstands wet, under the prescribed conditions of test
wide face(of a pole with rectangular cross-section) pole face through which the major axis passes
wind loading load imposed by wind pressure acting at right angles to the conductor and the structure
wind span horizontal distance between the points at mid-span on each side of a support
windspan length of conductor calculated on the design span upon which the wind acts
NOTE It is the sum of half wind loading on each of the two adjacent spans.
wind span (of an overhead line) sum of those portions of span lengths on either side of the structure that, when subjected to wind, impose a horizontal load on the structure
NOTE The maximum wind span is dependent upon the ability of the structure and its foundation to resist the overturning moment caused by the action of the wind.
winding assembly of interconnected turns or coils intended for common operation (or both)
NOTE A winding is provided with terminals and is intended to produce a magnetic field when carrying electric currents or to produce voltages between appropriate points when placed in a time-varying magnetic field or moved through a magnetic field.
145 NRS 000-1:2008
winding set of coils that is wound in series with a conductor for the transformation of current or in parallel to a conductor for the transformation of voltage
NOTE The number of rings in a coil determines the transformation value of voltage or current.
wiping gland non-ferrous metal bush fitted to an enclosure to which the metal sheath of the cable is plumbed, to which the armour is clamped and which seals and secures the cable to the enclosure
withstand voltage value of the test voltage to be applied under specified conditions in a withstand test, during which a specified number of disruptive discharges is tolerated
NOTE The withstand voltage is designated as:
a) conventional assumed withstand voltage, when the number of disruptive discharges tolerated is zero. It is deemed to correspond to a withstand probability Pw = 100 % (this is in particular the case in the low-voltage technology);
b) statistical withstand voltage, when the number of disruptive discharges tolerated is related to a specified withstand probability, for instance Pw = 90 %.
work refers to all physical activities in connection with apparatus, excluding operating activities and other non-dangerous activities that will not affect the health and safety of workers or the safe operation of apparatus
work permit document(s) for the authorization of all work to be done on any supply system or apparatus
NOTE A work permit can include the application, permit, clearance and workmen’s declaration documents.
work permit form printed form that contains the application, permit, clearance and workmen's declaration for the authorization of all work to be done on any supply system or apparatus
working clearance minimum safe distance to be observed between normally exposed live parts and any person working in a substation [IEC]
working clearance straight-line clearance between the live part and the position of the feet where a person might be required to work
NOTE The working space is the region within the boundary of the working clearance where a person can safely work on dead equipment.
working earth supplementary portable earthing device that is used on apparatus in such a position that it is visible from, and applied as close as possible to, the point of work. This includes personal earths and bonding/shunt conductors
working pole; working stick insulating tool made of insulating tube and/or rod with end fittings [IEC]
working standard measuring instrument that has been calibrated by an approved calibration laboratory or an approved test laboratory, and that is used for the calibration of meters and metering equipment
working standard standard which, usually calibrated against a reference standard. Is used routinely to calibrate or check material measures, measuring instruments or reference materials
146 NRS 000-1:2008
wrapping one or more layers of an insulating material wrapped around all the cores of a cable before the shield or sheath is applied
XLPE cable single-core and three-core, cross-linked polyethylene (XLPE) insulated, electric cables
zone capacity capacity associated with a development based on the type of development in the area and the average coverage (floor area ratio) such as industrial development with a high capacity required per square meter
zone sequence co-ordination feature that allows devices to maintain sequence co-ordination for combinations of rapid and delayed trip operations. The upstream device senses the presence of a fault and so the clearance of that fault (by downstream device) and proceeds to the next trip operation in its sequence
zone sequence co-ordination feature that allows protection devices to maintain sequence co-ordination for combinations of rapid and delayed protection operations.
zone sequence co-ordination insulation feature that allows protection devices to maintain sequence co-ordination for combinations of rapid and delayed protection operations
© SABS
