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DOC. NO. KOC-E-006 II Page 1 of 53 Jl REV. 3
STANDARDS PUBLICATION
KOC RECOMMENDED PRACTICE
FOR
POWER SYSTEM STUDIES, PROTECTION AND CONTROL
DOC.NO. KOC-E-006
STANDARDS TEAM
I DOC. NO. KOC-E-006 II Page 2 of 53 II REV. 3
3
KOC RECOMMENDED PRACTICE
FOR
POWER SYSTEM STUDIES, PROTECTION AND CONTROL
21/12/2010
DOC.NO. KOC-E-006
ISSUING AUTHORITY:
STANDARDS TEAM
Issued as KOC RP Task Force
(TF- EE/07)
Rev. Date Description Snr. Eng}! Stds. Tea~ ~. ndards
Tel. 61633 . 61896
Page 3 of 53 3
FOREWORD 6
1.0 REVISION HISTORY 7
2.0 SCOPE 8
3.0 APPLICATION 8
4.0 TERMINOLOGY 8
4.1 Definitions 8 4.2 Abbreviations 8
5.0 CODES & STANDARDS 9
5.1 Conflicts 9 5.2 of Standards and Codes 9
6.0 ENVIRONMENTAL CONDITIONS 11
7.0 HEALTH, SAFETY AND ENVIRONMENT 11
8.0 POWER DISTRIBUTION AND FAULT CONSIDERATIONS 12
8.1 Power Distribution 12 Effects of Faults on Power Distribution Systems 12
8.3 Fault Current Calculations 12 8.4 Equipment Current Ratings 14 8.5 Methods Limiting Currents 14
9.0 POWER SYSTEM STUDIES 16
1 16 Conventional Studies 16
9.3 Power 18 9.4 Harmonic Analysis 19
Motor Starting Studies 19 Protective Relay Coordination Studies 19
10.0 POWER SYSTEM 20
10.1 Motor 10.2 Overvoltages 21 1 Harmonics 22 1 Power Factor 22
Page 4 REV. 3
11.0 POWER SYSTEM EARTHING 23
11.1 11.2 Solidly Earthed Neutrals (For Systems 3.3kV and below) 11.3 Impedance Earthed Neutrals Systems above 11.4 Un-Earthed (Isolated) Neutral 11.5 24 11.6
12.0 POWER SYSTEM PROTECTION 25
12.1 General 12.2 Protection 12.3 Transformer (CT) 29 1 Voltage Transformer (VT) 30
13.0 POWER SYSTEM PROTECTION SCHEMES 30
13.1 Incomer Protection 13.2 Protection 1 13.4 Protection 13.5 Protection 1 Motor Protection 13.7 Shunt Capacitor Bank Protection 45
14.0 POWER SYSTEM CONTROL 46
14.1 1 Remote and Controls 14.3 Switchgear Controls 14.4 Automatic (ABT) 1 Generator Controls 14.6 Motor Controls 48 14.7 1 Bank Control & Metering
15.0 ALARMS AND INDICATORS 50
16.0 QUALITY ASSURANCE 50
17.0 DOCUMENTATION 51
17.1 17.2 Deliverables
ACKNOWLEDGEMENT
3
DESCRIPTION
Revised Foreword Revised Clause 1: Added revision histo
3 Added few Standards to International Standards in
4 I Added new sub-Clause 9.3-"Power Factor Studies" 5 Added new sub-Clause 6 Revised sub-Clause 10.4 7 I Added new sub-Clause 1
8 Added new sub-Clause 1 Bank Control & Meetin
131
" new sub-Clause 17.2 (f)-"Power Factor
51 of 53
PAGE No.
existing list of National I 5.2.1:
Capacitor
8 - "Shunt Capacitor
52 of 53
REV. 3 DOC. NO. KOC-E-006
131
This document "KOC Recommended Practice for Power System Studies, Protection and Control" (KOC-E-006 3) is intended to provide minimum requirements the power studies and selection protection & control schemes for the electrical distribution networks previous document 'KOC Recommended for Power Protection Control' (KOC-E-006 Rev. issued in June
KOC Facilities in Kuwait.
has incorporate latest stipulations by MEW the improvement of Power
Recommended Practice has been approved by Standards Team in consultation with Standards Technical Committee (STC) for use throughout corporate Engineering
operational functions of Kuwait Oil Company (KS.C.).
This Recommended Practice (RP) sets out to achieve the following objectives:
a) To to be followed for Power Studies, design & selection of protection and for electrical networks within KOC.
b) provide a establish the to form the
c) To and environment established by KOC's
of safety and protection
(HSEMS)
plant, personnel
Health & Health,
Management System and (H&E) Guidelines.
Feedback as well as any comments or derived from the application this Recommended at any stage design, installation or operation are invited and should directed
Team Standards (Chairman, Standards Technical Committee) Industrial Group,
- 61 State of Kuwait.
Task Force responsible for the revision of this Recommended Practice
The revision of this Recommended Practice was by Technical Committee to the Task comprising of following members:-
Mr. Unnikrishnan Force Tel No. 61633 Mr. Andrew Nayak Projects Team Member Tel No. 61658 Mr. Hani AI-Awadi (S&EK) Team Member Tel No. Mr. Pattnaik Design Team Member Tel No. 61294 Mr. Ramalingam Member Tel No. 20350 Mr. Athol! Robertson Tel No. 792 Mr. Sajid Sheikh Member Tel No. 61680
DOC. NO. KOC-E-006 Page 7 of 53 REV. 3
1.0 REVISION HISTORY 131
1.1 Rev. 3: For incorporation of MEW stipulations on "Power Factor Improvement".
1.2 Rev. 2: For updating and amalgamating the Power System Protection, Control and System Studies requirements given in various KOC documents stated below into a single KOC RP with a view to unify the requirements and avoid duplications:
a) "KOC Recommended Practice for Power System Protection and Control" (KOC-E-006 Rev.1)
b) "KOC Code of Practice for Electrical Systems and Installations Part 3 Power System Design" (COP-E-002, Part 3)
c) "General Specification for Electrical Engineering" (KOC Std. 381/020)
d) "Engineering Group Specification for Electrical deSign, Installation and Testing" (015-PH-1901)
Note: The requirements covered in this revised "KOC Recommended Practice for Power System Studies, Protection and Control" (KOC-E-006 Rev. 3) shall supersede similar requirements covered in existing KOC documents mentioned in clause 1.2 of this RP, until those documents are withdrawn.
DOC. NO. KOC-E-006 REV. 3
2.0
2.1 This Recommended Practice (RP) describes minimum requirements for power studies, guidelines for design protection & control the distribution networks within KOC facilities.
This does not cover any specific requirements for electrical systems with above 11 kV and requiring MEW (additional
requirements if any, from MEW shall into consideration before finalizing system design).
3.0
3.1 The Power System Studies, design and selection of protection system and control schemes conform to the requirements of this Recommended Practice, except as modified or supplemented by the project specification(s) or data sheet(s).
Any exceptions or deviations from this Recommended Practice, along with their merits and jusUfications, shall be brought to the attention of KOC's Controlling Team for their review, consideration and amendment by Standards (if required).
3.3 Compliance with this KOC Recommended does not of immunity from or statutory obligations.
4.0 TERMINOLOGY
4.1
of Recommended Practice, the following definitions apply.
1.1 Contractor
person, persons, firm or company contracted by KOC undertake the execution of Work by the Contract.
4.1.2 KOC Controlling Team
Any KOC Team authorized to initiate a of a project or procurement of materials I eqUipment for KOC.
4.2 Abbreviations:
AVR
CT
HRC
HSE
Automatic Voltage Regulator
Transformer
High Rupturing Capacity
Safety and Environment
REV. 3
HSEMS
HV
Hz
kA
KOC
LV
MCC
MEW
N/C
N/O
REF
RMS
VA
VT
Health, Safety & Environment Management System
High Voltage
Hertz
Hydrogen Sulphide
Kilo Ampere
Kuwait Oil Company (K.S.C,)
Light Diode
Low Voltage
Motor Control
Ministry of Electricity & Water
Normally Closed
Normally Opened
Earth Fault Protection
Root Mean Square
Temperature Detector
Volt-Ampere
Voltage Transformer
5.1
In the event of conflict between this Recommended Practice and the latest edition of standards I codes herein, or other or contractual
most stringent requirement shall apply,
List of Standards and Codes
The electrical system design and selection of equipment shall conform, except where otherwise , with the current issues and amendments of the applicable codes and standards, including but not limited to the following:
1 International! National 131 60034-11 Machines: Thermal Protection
60044-1 Instrument Transformer-Current Transformer
60044-2 Instrument Transformer-Inductive Voltage Transformer
DOC. NO. KOC Page 10 of 3
60044-5 Instrument Transformer- Capacitor Voltage Transformer
IEC 60051 Direct acting indicating analogue electrical measuring instrument and their
60076-6
60255 Relays
60269 Low-Voltage Fuses
60439 Low-Voltage Switchgear and Controlgear
60747-6 Semi-Conductor ."""""''' Thyristors
60871
60909 (0-4)
60947
61000
61642
61921
1-200
Std.141
Std. 519
Self-Healing for AC Voltage up to and including 1 kV
Power Systems Having Rated Voltage above 1000V
Circuit Current in Phase
Low-Voltage ....'AfITrr'n Controlgear
Compatibility
Industrial a.c. networks affected by harmonics - Application filters and shunt capacitors
Power Capacitors - Voltage Power
Shunt Capacitors
High Voltage Switchgear Controlgear - AC Metal Switchgear and Controlgear for Rated Voltages
1kV and up to and including 52kV
Recommended Practice for I-In\A/.,.r Distribution for Industrial Plants
Practice for Control in Electrical
Electrical Code
for Electrical Safety in Work Place
5.2.2 KOC Standards & Recommended Practices
KOC-E-001 for High Induction Motors
guidelines (Health,
& procedures,
11 of 53 3
for High Voltage Switchgear ControlgearKOC
KOC-E-003 KOC Recommended Electrical "":""''1'",,",,,<:,
Design Part 1 Selection
KOC-E-004 KOC Recommended Practice for Selection, Installation and Maintenance of Electrical Equipment in Hazardous
KOC-E-009 KOC Standard for Low Voltage Switchgear
KOC-E-010 KOC Standard for Low Voltage Induction Motors
KOC-E-024 KOC Practice for and Bonding
KOG Standard Hazardous Classifications
KOG-G-004 KOC Standard Packing, Marking and Documentation
KOG-G-007 KOC Standard Basic Design
Project
In addition to KOG Standards and herein, the Controlling Teams in shall designate as required for the specific Project.
Recommended
6.0 ENVIRONMENTAL CONDITIONS
6.1 The environmental conditions in Kuwait are severe and shall be considered while Power Electrical equipment for outdoor
installation shall suitable for continuous operation at a high ambient temperature and humidity. The atmosphere shall be to be dusty and corrosive and may contain traces of hydrogen sulphide.
location
6.2
7.0
to "KOC detailed
supply conditions
which provides environmental, site and utility
KOC Facilities.
7.1 All relevant requirements of KOG Management System) Regulations, guidelines international be
7.2 It be ensured that all electrical are identified and necessary control measures are in place for the designed system.
DOC. NO. KOC-E-006 Page 12 of 53 REV. 3
8.0 POWER DISTRIBUTION AND FAULT CONSIDERATIONS
8.1 Power Distribution
The proposed power distribution scheme for a particular project shall be shown in single line diagram for each voltage level in accordance with the requirements given in "KOC RP for Design Basis and Selection of Electrical Systems" (KOCE-003, Part 1).
8.2 Effects of Faults on Power Distribution Systems
8.2.1 Bolted three phase faults on the system will depress the voltage at the point of fault and downstream of the fault to zero. All locations between the source of fault current and the fault shall experience reduced voltages. This condition shall apply until the faulty section has been cleared at which stage voltages will be rapidly restored.
8.2.2 The following effects of three phase fault shall be considered for investigation:
a) Possible loss of synchronism between parallel running synchronous machines. This would only be likely for dissimilar machines or for identical machines connected to the fault which are not electrically symmetrical.
b) The possibility of motor contactors dropping out and the consequential need to re-start the motors, either manually or automatically.
c) Possible extinction of certain discharge lamps and the time for re-ignition. (The provision of emergency lighting systems may avoid the need to feature this).
d) Loss of electronic and control equipment supplies resulting in maloperation (The provision of DC or 'no break' supplies for vital loads may avoid the need to feature this).
e) The extent of overvoltage on the system components resulting from fault clearance. This could cause unacceptable transient recovery voltages occurring for short periods which may have a destructive effect on electrical insulation.
8.3 Fault Current Calculations
8.3.1 The short circuit current that flows as a result of fault shall be calculated at each system voltage for both three phase and phase to earth fault conditions. These calculated currents shall be used to select switchgear of suitable rating and to allow the selection and setting of protective devices to ensure that successful discriminatory fault clearance is achieved.
8.3.2 The voltage disturbance sustained during the faults and after fault clearance shall also be ascertained to ensure that transient disturbances do not result in loss of supplies due to low voltages or overstressing of plant insulation due to high voltages.
DOC. NO. KOC-E-006 Page 13 of 53 3
8.3.3 fault current calculation shall include fault current generators and from induction I synchronous motors. the
DC asymmetrical components fault be calculated voltages. Fault contribution from Grid shall exclude any
decrement with fault duration. Maximum and minimum values fault currents consistent with annual load cycles shall be from MEW.
impedances shall be used for calculating balanced three phase faults. Positive, negative and zero sequence impedances be for calculating unbalanced
Three balanced fault current calculations shall carried out to obtain prospective circuit breaker ratings and shall inClude:
Asymmetric making capability, expressed in peak OlrnnClrcc calculated half a cycle after fault inception. Both and current decrements shall be included for half
b) Asymmetric breaking capability, at a at which the contacts are to and a maximum of 10 milliseconds for instantaneous type protection operation. Both AC and decrements shall be included for selected time.
c) Symmetrical breaking capability, in calculated a as in item (b) above. This assumes nil DC current components and shall allow for decrement for the time.
fault currents be no than the maximum currents for solidly earthed systems, under normal operating conditions.
with neutral solidly earthed, earth fault current may greater than phase fault current. On the fault are limited by
neutral eqUipment, currents may be assumed to include no and shall be considered constant whatever the level of bonding conductor and faulted
and components of motor fault current contributions shall calculated for prospective fault currents. At the instant fault inception, AC symmetrical component and DC identical.
taken as the peak direct-an-line starting current, this being dictated by the rotor locked rotor reactance. Both these currents shall taken decay exponentially with time using and short circuit respectively.
calculation of individual fault current contributions shall be carried out individual motors of significant ratings on the power motors with ratings 500 kW should treated in this way.
8.3.8
DOC. NO. KOC-E·006 Page 14 of 53 REV. 3
8.4
8.3.9 All other motors on the system may be treated as a number of typical equivalent motors of total rating rotating loads, at different locations.
ratings of these equivalent motors shall selected be consistent with the actual drives at a given location.
1 All switchgear and distribution equipment on the power system capable of carrying the prospective symmetrical fault currents for specified short time duration one (1) or three (3) without deleterious between one (1) and three (3) second shall be dictated by availability,
and fault current protection clearing times.
8.4.2 (3) short ratings are preferred high voltage (3.3kV and levels to avoid the necessity for rapid protection. The back-up current protection clearing times shall less than the equipment short time current ratings.
8.4.3 The of circuit breakers shall be on the make and break duty which the breaker is required to cater fOL Switching that may closed on to a fault shall the fault making capability.
8.4.4 The closure of on a or unbalanced fault shall not result in shock load damage to healthy parts of the system as a asymmetrical making currents flowing.
8.4.5 For systems protected by fault current limiting HRC type fuse characteristic may be taken into account in assessing short circuit duty of system.
For standard values of short time current ratings at various voltage "KOC RP and Selection Systems" (KOC-E-003,
1).
8.5 Methods of Limiting Fault Currents
8.5.1
The power distribution system shall designed provide the required and quality of supply with prospective fault levels within the
capability of commonly available switchgear.
b) equipment shall be capable of withstanding maximum short circuit when operating in with the requirements given
in KOC RP Design and Selection of Electrical Systems" (KOC003, Part 1), unless specified.
15 of 53 REV. 3 DOC. NO. KOC-E-006
c) case of system prospective short circuit requirements exoeea the following <:l11"~~rn<:ltl\JO'"maximum allowable circuit breaker
should be considered:
i) Increase the rnOlrl"'l::I
reactance, this causes no other technical or problem.
to with certainii) Change mode by
reinstate the supply open and provide auto-transfer security and quality
iii) Purchase switchgear and equipment to the higher circuit levels if are available.
iv) Provide fault limiting devices other
v) Carryout any combination of the alternatives in items (i) to (iv)
of the most appropriate be subject to of the to (iv) given
based on cost by KOC.
Series
Where series are used to the reactance the source and potential location, the following shall be taken into consideration require KOC approval:
a)
single or three shall have a
symmetrical current at
b) power operating
'-IV,""'''.I''''. series reactors shall which minimize
located in positions within the and losses under normal
The voltage through series reactors under the motor start, or re-acceleration conditions shall be checked to ascertain no unacceptable transient undervoltage occurs.
8.5.3 Any use of other short limiting devices such as IS limiters and links (short circuit limiting couplers) or be avoided wherever possible and shall approval by
DOC. NO. KOC-E-006 Page 16 of 53 REV. 3 II II
9.0 POWER SYSTEM STUDIES
9.1 General
9.1.1 Power system studies shall be conducted to evaluate the performance, reliability , safety and economics of a power system. These studies shall be carried out in the design stage to identify and avoid potential deficiencies in the system.
9.1.2 The design aspects of power system for new installations and modifications to existing plants shall be studied using network analysis computer programs to aid analysis, where necessary.
9.1.3 The power system studies and its analysis shall be used:
a) to define equipment parameters before purchasing.
b) to select control and protective relay settings.
c) to ascertain the system reaction to normal and abnormal operating conditions etc ..
9.1.4 The power system studies shall be carried out with terms of reference approved by KOC. The software programs and computer capability shall also be approved by KOC. Models for power system studies shall be sufficiently detailed and proven to give confidence in the results of the studies.
9.2 Conventional Studies
Conventional studies shall include Load flow analysis, Short circuit studies, and Stability studies.
9.2.1 Load flow analysis
Load flow analysis checks voltage profiles and circuit loading under steady state conditions, which shall be used to predict the performance of the electrical system under various operating conditions.
9.2.2 Short circuit studies
a) Short circuit studies help to ensure that system components are appropriately sized to withstand the mechanical and electrical stress of the fault currents prior to clearing. These studies shall be used for switchgear specification and control, protective relay application and setting purposes.
b) Short circuit calculations are performed to analyse fault currents that might flow under a variety of symmetrical, asymmetrical and unbalanced fault conditions.
REV. 3
earth faults at all busbars and extremities of the power system shall determined using
studies.
c) The current flows for three phase, phase to
d) setting and application of short circuit studies may adopt a simple approach to motor contributions. In this induction motor contributions based on locked rotor shall only be relays that operate in less than and may ignored for slower acting relays.
9.2.3 Stability studies
a) transient and dynamic performance power systems after large changes and fault disturbances are analysed by stability studies.
shall to
i) The ability of the system to stay in synchronism.
ii) Induction motor stability start.
iii) Re-acceleration and re-start schemes.
iv) of
They should also be used consider technical
v)
vi) Parallel or open operation of radial feeders.
vii) Operation of fault limiting
viii) Installation of switched reactors or capacitors, etc.
b) stability shall
i) Dissimilar on-site
ii) Synchronous motors.
"'<>rl~""'i"i out on ",,,,,,ton"!,,,
transient stability studies shall be used to determine whether synchronous machines are to fallout of synchronism after the most severe single disturbance.
d) Where transient stability are carried out in order to assess the ability of generators to remain in synchronism after a fault, the steady state operating condition before the fault is applied be one in which the spinning reserve of generation is kept at a minimum due to assumed maintenance of
REV. 3 Page 18
induction motor stability studies be out to performance of the system after a major disturbance
period from fault inception to the time when steady state equilibrium is reached. They shall require AVR and governor modelling as
the return to state will positively in to . Loss of frequency, loss voltage and loss of
induction motors shall be checked with studies.
time
f) Induction to demonstrate ability to start, re-accelerate or restart motor loads without their stalling or
mO~ffi fue
g) Where motor re-start schemes are required, induction motor stability studies shall be used to define the maximum number and magnitude of the various stages re-start that will after
without voltage disturbance.
h) stability studies shall carried out to the of the power supply component an fault or a mechanical trip
tripping under overload. Reacceleration studies determine
131
i) Where the frequency drop is predicted to exceed under-frequency load shedding schemes shall be In such cases, stability
shall define minimum number and magnitude of the various stages of load shedding that will be keep frequency within acceptable limits.
9.3.1 The Scope of Power Factor Study should cover types of Facilities I Load patterns in KOC Network, Office I Housing, etc.) as applicable to identify the reactive compensation solution that is best to a particular network for achieving power factor specified.
study should evaluate the merits of the technologies considered under various plant operating conditions. The control strategy shall be designed to cope with plant upset conditions, starting I large motors. study shall not following:
• Identification of the best suited PF improvement system for the type of KOC Facility under consideration.
• location of installation of improvement system (Centralized, Group or localised), rating and voltage levels.
• The requirement Automatic Power controllers.
• The voltage rise and switching transients associated with CalJaC;ltors its mitigation.
1
DOC. NO. KOC-E-006 Page 19 of 53 3
• Harmonics I resonance of same by filters I detuning.
.. Grounding methods, Protection and metering the bank I improvement system,
9.4
9.4.1 A harmonic analysis of the electrical should be whenever producing loads (non linear loads which include static power
converters, saturated magnetic devices, arc discharge devices, a total rating a system anyone voltage level or
analyse the magnitude and location of harmonic distortions within
9.4.2 131 Where capacitor banks are to be installed for improvement of power factor, special attention shall be given for harmonic analysiS of the
to ensure that the harmonic levels are within system under consideration.
tolerable limits
where there is concern about harmonic levels being excessive. The study shall be used power system.
power system. Motor starting and minimise
normal full load current and shall
impact of motor
carried out in order to or verify such as circuit breakers, and
used in the protection schemes so as to to personnel and equipment while causing least disruption to power
zones covering shall adequately protected
of a fault.
9.6.3 of protective and their shall dictated by the ability to whilst maintaining normal operational integrity, and to ensure co-ordination is obtained with other that are in the same chain under consideration.
9.6.4 A graded properly coordinated of protective shall be as as practicable to provide a selective fault clearing system which
allows the circuit switching device to a fault operating
9.6.5 The protective system shall be based on of overlapped protection, that is, in case of failure the short circuit fault
trip, the protective device of the succeeding equipment shall function to the fault.
3DOC. NO. KOC-E-006 Page 20 of 53
The power system transformers, busbars
9.6.6 shall be divided Incoming and outgoing Faulty
disconnected with minimum of time while maintaining power supply for the healthy sections. Successful discrimination shall be achieved by proper settings in time and in current pick-ups between various equipment. Selectivity interval shall 0.3
10.0
10.1 Motor Starting
10.1.1 Power systems shall designed as far as possible to sustain (DOL) starting of all The
DOL a particular voltage shall dictated by limiting the maximum voltage drop at the motor terminals during starting to 15%, In addition, when starting any the voltage at any switchboard busbars not below 90% the shall sized to meet these
of motor shall
10,1.2 dips during accelerating and the voltage dips not causing
to the power The starting of the largest and most remote located motors at all voltages shall to ensure that no problem Where voltage during motor starting are to the following solutions be considered in the order of precedence given:
i) Obtain a with a lower current.
ii) Increase the short circuit to a level beyond those given in KOC-E-003 Part 1 by decreasing system source impedance up the motor busbars, if
higher level switchgear is available, The selection this alternative is subject to approval by KOC,
iii) Consider start such as start' reduce voltage dips if solution is limited to a few specific motor drives.
iv) Any combination of (i) to (iii) above,
Reduced voltage starting of specific found
may be subject to prior approval if it is be economical and the additional complication associated with assisted start equipment is operationally acceptable.
10.1 motor load shedding schemes are to be adopted, they shall designed ensure that terminal and busbar voltage depressions throughout the system
do not drop below values in section, method of initiation of based upon low system frequency may be adopted applicable, subject to prior approval by KOC.
21 of 53 REV. 3
10.1 Other means such as selective tripping of so loads depending upon rCl ....~ClnTC' could applied. The adoption any such scheme
and its design parameters shall subject to approval by KOC.
1
1 1 Overvoltages due to charging shall avoided by effectively earthing the and all metallic structures that mayor may not contain
conductors. Physical voltage systems shall be by using metal enclosures and barriers wherever practical
the two systems. Overvoltages this type transformer windings shall limited by effectively earthing neutrals the C"Of"'",nr<
systems. an Autotransformer is used, it shall have the neutral
1 0.2.2 Resonant inductive-capacitive occur when normally unearthed are an inductive Thus prospect of
resonance or ferro-resonance should be avoided by solid earthing the neutrals of systems up to and including 3.3 kV and resistance earthing the
of above kV. to resonance o11".::,,...t,,,
shall neutral systems, or systems with high impedance earthing. effects shall also considered when power c"crcl"Tl
eqUipment is or could operated without a neutral periods of time.
10.2.3 Intermittent earth faults on unearthed neutral systems may cause "'''U;:;''·Hr\lT'':>I"'IOC'
the order of or six times voltages. Neutral or earthing for fault line to charging currents, should eliminate these prospective overvoltages.
10.2.4 Current zero arc extinctions commonly result in overvoltages switchgear is fault conditions the healthy side of the system endeavours to return to the normal system voltage, but overshoots.
10.2.5 Switchgear and power equipment to ensure that the transient recovery voltages produced by the switchgear arc-extinctions do not exceed insulation capability of the system. The introduction resistance during fault current flow by special means or by using switchgear naturally high arc should reduce value of
recovery voltage is generated.
10.2.6 Unsynchronized systems may be by switchgear two synchronous machines have out of step and are 180 degrees out
This out of switchgear operation may also occur when an induction motor is reenergized by when residual voltage the motor is still of a similar magnitude to system voltage. former problems circuit be for satisfactory operation under of conditions whereas the shall be avoided by time delayed re-energising
Page 22 REV. 3
10.2.7 production high overvoltages to the forcing of a current zero occurs most commonly with fuses and vacuum
overvoltages to Current limiting shall
only they are designed the insulation withstand value equipment used in Such of a particular voltage rating shall never be
of lower operating voltages.
10.2.8 use of vacuum switches is considered they shall to acceptable withstand for a particular
provision of surge limiting equipment on the vacuum switch.
equipment
l"Y\o.Tnr,,",C" agreement between KOC
overvoltage to which
Inrn,Qnf by travelling down lines may require to
for protection will be
Lightning
systems are subjected are those caused by lightning. avoid on outdoor electrical equipment, all
shall overvoltages can reach the Sites which are by MEW via
against and the
10.2.9
10.3
10.3.1 Harmonics in the power result in power losses overheating of
in accordance with
machinery, on communication and circuits, of capacitor banks maloperation of electronic equipment. Every attempt shall rn<:>r<:>T.nrt:> be taken to reduce harmonics to acceptable
10.3.2 Circulation of harmonic resulting from in parallel should avoided by the means clause 11 of this RP.
1 Wherever significant amount of recti'ncation or inversion equipment is purchased, possible use of phase transformers or shall be taken
into account and an shall subject to KOC approval. The presence of harmonics in common earthing systems shall
and limited if are considered to cause prospective hazards. more guidance on harmonic control in electrical power systems, IEEE Std. shall be referred.
10.4 Power Factor 131
1 1 capacity to the
distribution
Improvement of power shall be in order to comply requirements, to
the system loss.
1 The latest MEW regulation (Rule No.5) stipulates maintain a minimum ,",,,\..,or
factor of which shall be followed for all electrical installations in KOC, in the
1 system shall out in with the guidelines cn<:'I"',r,
on the system study carried of this RP, to ensure the
correct rating and of equipment.
DOC. NO. KOC-E-006 Page 23 of 3
10.4.4 The type of power factor correction equipment selected shall be reliable, based on proven technology to provide trouble operating
as applicable.
10.4.5 power improvement system shall be installed at appropriate locations so as to maintain the power factor between "0.95 lagging and Unity".
11.0
11.1
11.1.1 general guidance on neutral earthing are described in this For on earthing of equipment and "KOC
Recommended Practice for Earthing Bonding" (KOC-E-024) shall be referred.
11.1.2 earthing of each part of a power system operating a voltage shall considered individually. Where such systems are required to earthed
solidly, or via impedance, neutrals shall be to a common plant earthing system. shall a to that ensures operation of protective devices in various circuits and shall not be in excess of four (4) ohms.
11.1.3 equipment shall be provided at or both, which have neutral brought out which are the
source of power to the distribution system at any specific voltage. In cases where the power sources are delta do not brought out, neutral earthing may out other star on the system or by the provision of earthing transformers.
11.1 Electrical systems operating a common voltage which may be normally or abnormally run "unparalleled" shall a neutral provided for The earthing shall be designed to ensure that there is no possibility of inadvertently operating a system with an isolated neutral.
11.1.5 Earthing conductor sizes shall selected dynamic fault and to provide minimum protection Stranded copper or copper rs shall normally be used for earthing conductors and shall insulated with green and yellow PVC, where insulation is
withstand maximum thermal and
11.2
11.2.1 Power systems operating at 3.3kV and below shall have their neutrals connected to the plant
11 The earthing for three (3) phase transformers shall low winding star and transformers at winding ends or centre pOints.
a HnlT';;'''':;;' below 3.3kV shall only11 Impedance to
11
11.3 Impedance Earthed Neutrals (For Systems above 3.3kV)
neutral earthing equipment to limitat 11 kV, provided in the neutral connection to the plant
winding with an shall be used with the limiting MVA and duration to meet
the protection requirements.
11.3.1
11.3.2 the power at the specific contains no direct generators under any mode of operation, the connection shall following order of
a) At the source star connected transformers.
b) At other star nt:>r'Tt:>n power transformers.
At
The neutral shall comprise a resistor with a ten (10) second fault rating reduce the fault current to the full load rating of the power source transformer. The use of reactors to earth neutral systems shall be only to approval by KOC.
11.3.3
equipment shall provide for either system operating independently. The
a specific voltage is supplied from in with source the neutral
neutral earthing equipment shall, wherever practical, be If'ft:>nrlr'!l
power sources and comprise ten (10) seconds fault rated, solid resistors. The of resistors shall the fault between half and full load rating of the lowest rated power current is
to distribution system earthing protection discriminatively.
11 Where the normal ratings of the source transformers and parallel running are significantly different, the resistor rating shall be dictated by the
requirements to ensure that most insensitive fault protection on any incoming or outgoing circuit positively with smallest source of earth fault current connected to the system.
Metal frame for outdoor use and be corrosion
11
An un-earthed or isolated system shall be only to approval by KOC.
11
11 1 Direct connected generators limited to f'I", •.,t:>r·"tA,r",
earthed. However. capacity the
nor,or<,tAr is approximately equal to the current level required to operate the distribution system protection.
DOC. NO. KOC-E-006 Page 25 of REV. 3
11 used for direct where the earth value required to operate the distribution system
protection. The resistor shall be of the ten (10) fault rated, solid and its impedance shall be to a between the half and full load current rating of machine, provided is sufficient to operate the distribution system protection system selectively.
11 connected generators are operated in parallel and earthed either solidly or through resistors, the provision neutral switchgear for generator shall be considered to avoid third harmonic current flows their heating effect.
11 Where such neutral switchgear is provided, it shall in a manner ensure that one and only one neutral switch is always
a Neutral switchgear may comprise contactors on schemes instead of circuit breakers where this is economical.
11 The provision of neutral switchgear schemes may be avoided, if identical-pitch generators are paralleled or if provision neutral earthing
reduces the prospective third harmonic currents to acceptable level. A 1% or less derating as a of third harmonic currents shall considered acceptable.
11.5.6 Where generators are connected to distribution switchgear via. unit-transformers, the generator neutral shall connected to earth the primary winding of a phase winding of which be shunted by a resistor with an ohrnic value approximately equal to the zero sequence capacitance for generator winding system.
11 primary voltage generator earthing shall be taken as the generator phase voltage although of 1% times line
voltages will standard transformers. ratings shall the product of the primary current and rated primary
voltage using a Thirty (30) second (6 times overload factor) duty
be provided with insulation suitable for the phase phase voltage of the to which they are connected. They shall designed to carry their rated fault current for the times specified in the preceding clauses, without any their component parts.
to neutral
11
12.0
1 General
1 1.1 The of power system protection schemes shall wherever possible considered in details at early design stage, whether for new plant extensions or modifications, and shall be based on fault calculation
12.1.2 for
design shall include protection relays with adequate setting ranges to allow all types and magnitudes of prospective short earth faults
and
DOC. NO. KOC-E-O 26 of 53 REV. 3
12.1.3 The protective relay application divides power into zones and I or equipment types having their own or other devices to determine the existence faults and to instruct appropriate circuit switches to isolate the fault. The choice of which provides protection electrical fault in time.
12.1.4 In high voltage protection "'('1"","' ......,'" protection shall by provision of sufficient voltage and current transformers correctly
located selected for rating and ratios, in to give full overlapping zones
12.1.5 Back-up protection shall be provided main protection schemes against the possible of either a main protection relay or a circuit breaker trip mechanism. At one independent means of back-up protection shall be provided to cater failure of the primary protection system where applicable.
12.1.6 The protection system shall designed take into account of the following
particular shall be that
criteria:
a) Reliability
b) Speed
c) Selectivity
d) Economics
e) Simplicity
Perform correctly when required and avoid unnecessary
Disconnect possible
Ability locate the fault and trip the minimum number of to only faulty zone or equipment.
Maximum protection at optimum cost.
Minimum eqUipment and circuitry for the required Protection.
12.1.7 All Protections shall be shown on the Line Diagrams for each level.
12.2
1 1 Protection relays shall be solid type, incorporating microprocessor based measurement networks and multiple characteristic selection having provision for communication with ESD & SCADA.
1 Protection relays shall be in with the requirements doors and shall be ofRelays shall be mounted on control
out flush mounted type with rear connections. shall dust
12.2.3
DOC. NO. KOC-E-006 Page 27 of 53 REV. 3 II
12.2.4 Relays shall be robust, stable in severe environmental conditions corrosive atmosphere.
operation and be suitable to of high temperature, high
withstand the humidity and
12.2.5 Each relay unit shall be withdrawable for unit interchangeability unless otherwise approved, and shall be provided with connections for a plug-in test block. For non-withdrawable units, a separate test block shall be mounted near the relay.
12.2.6 All protection functions may be integrated to one relay in place of a separate relay for each protection, unless otherwise speCified by KOC.
12.2.7 Auxiliary, alarm, tripping, master trip, intertrip, interposing and other relays shall be provided where required for effective operation of protection systems.
12.2.8 All protective relays shall have prOVisions for hand resets unless specified otherwise, and shall be capable of being reset without the necessity for opening the case. Relays shall be provided with LED indicators, which shall be visible from the front of the cubicle without opening the doors. LED brightness shall be such that they are clearly visible in normal artificial lighting levels. Flag indication in place of LED indicators is an acceptable alternative.
12.2.9 Self reset relays shall have an indication of operation until hand reset.
12.2.10 Tripping relays shall operate between the limits of 50% and 120% of nominal voltage.
12.2.11 Control relays shall operate between the limits of 80% and 110% of nominal voltage.
12.2.12 All relay contacts shall be silver plated and shall be capable of breaking the maximum current which can occur in the protection circuit in which the relay is located.
12.2.13 Test plugs or blocks shall be provided to allow relay testing and calibration from the front of the panel without disconnecting wiring. Relay terminals connected to current transformers shall be automatically short circuited when the relays are withdrawn.
12.2.14 Relays shall be capable of withstanding the output current of associated current transformers under fault conditions for the specified short circuit withstand time of the system under protection.
12.2.15 The auxiliary supply voltage shall be 11 OV DC or AC, as specified in the project documents.
DOC. NO. KOC-E-006 Page 28 of 53 REV. 3 II II
12.2.16 Inverse Definite Minimum Time Lag (IDMTL) Relays
Inverse Definite Minimum Time Lag (IDMTL) overcurrent relays, non-directional and directional, shall be inverse, very inverse or extremely inverse type as suited for the application, having adjustable current setting range and time multiplier setting range. Three (3) pole IDMTL overcurrent relays shall be provided for phase faults. The time and plug multiplier settings shall have wide range of choices with fine variations.
12.2.17 Instantaneous Overcurrent Relays
Instantaneous overcurrent relays shall be used for short circuit protection. The relays shall have high drop off to pick up ratio, low transient overreach, high thermal rating, and shall be immune to DC offsets. Three (3) pole instantaneous overcurrent relays shall be provided for phase faults.
12.2.18 Differential Relays
a) Generator differential protection relays, transformer differential protection relays and restricted earth fault relays shall all be high impedance, circulating current type, stabilised for through fault current and immune to DC offset of fault current or transformer inrush current.
b) Unit protection systems shall also be used for high voltage circuits, in particular high speed pilot wire feeder protection of interconnecting feeders. Balanced voltage systems (e.g. Solkor R) shall normally be used for feeder protection, but circulating current and carrier current systems may be approved or specified for particular applications.
12.2.19 Motor Protection Relays
Motor thermal overload and stalling relays shall have the necessary ambient temperature compensation to operate satisfactorily at the specified service conditions.
12.2.20 Undervoltage Relays
Undervoltage relays, with adjustable range and high drop off to pick up ratio, shall be provided for monitoring all the three phases, for the loss of mains supply. These undervoltage relays shall be used with suitable time delay relays for automatic transfer initiation. Tripping of high voltage motors shall be by separate time delayed undervoltage relays connected to each motor feeder on the busside. Instantaneous rated voltage relays shall be provided to monitor all three phases for restoration of mains supply. All undervoltage relay circuit fuses shall be coloured red.
12.2.21 Over Voltage Relays
Over Voltage Protection relays may be used for Alarm/trip applications and shall be used with suitable time delays.
Page 29 of REV. 3
12.2.22 Frequency Relays
relays shall continuously adjustable ranges from 47.0 to 52.0 with continuously adjustable pick up to drop differential from 0 to 1.0 Hz. relays shall complete with the provision to
operation due to harmonics.
1 Auxiliary Relays
Auxiliary shall be flush type with or indication and hand contacts. Auxiliary relays with inscriptions shall provided where as Buchholz alarm and trip, winding temperature alarm, trip, inter-
n,,,r·ol\.,,,,,, etc.
12.2.24 High Speed Relays
High speed, high burden lockout relays with cut off contact, hand provided for tripping I lockout each HV
LV Two normally open and two normally closed volt-free contacts shall be wired to a terminal block for provision shall be made to ensure that switching tripped on fault cannot be without manually resetting the master trip I lock-out relay. Lock-out relays shall disengage the closing circuit.
1 Protections
Surge arrestors may be required for protection voltage switching transients or applications.
HRC fuses shall be used for low voltage short circuit protection and also on high voltage They shall graded in any protection scheme
with due allowances for different temperatures and varying characteristics. rating of major fuse shall normally that of the next minor fuse in but the discrimination to 1 1 where fuse characteristics and system condition allow.
12.3
12.3.1 All current transformers shall comply with IEC 60044-1.
1 Separate shall for protection and metering duties. Current transformer primary current rating shall minimum 20% more applicable equipment rating unless otherwise specified.
1 Current transformers for metering shall be minimum 15 VA Class 1 otherwise specified. Current for protection be minimum 15VA Class 0 otherwise specified. Current transformers for use with circulating current protection and interface with supply protection shall be X to I 60044-1.
1
REV. 3 DOC. NO. KOC-E-006
12.3.4 The output of each current transformer shall in accordance with the preferred value for the circuit burden as listed in lEG 60044-1, and each protection current transformer be capable providing energy operate the protective devices with their minimum values.
1 transformers shall rated to withstand the thermal magnetic resulting from through fault current equal to switchgear short-time
withstand current rating.
12.4
12.4.1 All voltage shall comply with lEG 60044-2. They shall be 3P for protection purposes and Glass 1.0 metering.
12.4.2 The rated output capacity any voltage transformer shall 50% in excess output of 200 VA. if connected
the burden of equipment with a minimum The voltage shall be 110 V.
than of resistors shall be
for protection shall be 3-phase type for all directional and power protection schemes. VT's for metering shall also be 3-phase type unless otherwise.
13.0
13.1
13.1.1 Incoming supplies from MEW or KOG Interconnectors shall provided with following protections as a minimum:
a) High pilot wire
b) Non-Directional Overcurrent Earthfault W"'f',t"",t, (IDMTL) in case Single Incomer.
c) Directional Overcurrent and Earthfault Protection (lDMTL) in case parallel feeders.
13.1.2 Incoming supplies from MEW Transformers shall provided with the following protections as a minimum:
a) Differential Protection.
b) Directional and non-directional type in case
and Protection (IDMTL) case of parallel single incomer.
c) Protection.
d) Intertrip.
REV. 3 Page
be via a common reset lock out relay.
1
1 1
a) Generator protection should normally provided by equipment suppliers as part a total package specified
b) shall protected against internal faults including the following:
i)
il) phase earth.
iii) earth
1 Rated between 2 MVA and 1 MVA
a) Generator protection schemes machines in excess of 2 MVA shall consider following abnormal conditions as a minimum:
i) Overcurrentloverload/winding temperature.
ii)
iii) Unbalanced loading, (negative phase sequence).
iv) of ovr"t",1r.r""
v) Motoring or Reverse Power.
vi) voltage.
vii) Cooling water and air temperature detection.
viii) Over-excitation.
b) or high impedance differential protection shall provided to detect both stator phase and earth faults.
c} In addition protection, stator fault primary protection should be provided a low impedance earthing scheme is applied to the generator neutral.
REV. 3
e) Rotor Earth fault protection provided to and (not trip) on the occurrence of the first earth fault.
f) Stator phase fault back-up protection shall be provided by overcurrent protection. This is also required system faults.
shall of the voltage restrained or controlled energised from eTs in the neutral end the
g) Overload protection the stator shall be provided for all generators by embedding temperature measuring in winding.
h) Where system conditions could cause problematic overvoltages, an overvoltage protection arrangement should be employed.
i) Negative sequence protective relays shall provided unbalanced loading. The relay characteristic should match
of the
j) Loss of excitation nrrWQ('TI shall be provided.
power nor,:>.,-\,-", which could motor in of prime mover failure during operation. operation of any reverse power protection agreed with the manufacturer of the prime mover.
I) Undervoltage protection shall be provided to detect loss of supply to voltage transformers (VT). Where a VT is to supply the AVR and protective relays, undervoltage relay shall incorporate a definite time delay some three (3) seconds to preclude under
conditions.
k)
13.2.3 Generators Rated 2 MVA and below
Protection of should normally provided by manufacturers as part of a total package unless specified and shalt have the followingrunen.
features as minimum:
a) Overcurrent relays detect phase faults.
b) IDMTL earth fault relays for not normally run in parallel with fault power sources.
c) Restricted fault, high relays, internally looking or directionalised earth fault relays for which are run in parallel with
earth fault power sources. In the an IDMT Earth fault energised from a in the generator neutral shall provided
system back-up earth fault protection.
d) Reverse power relay for generators which operated in parallel with power sources.
3
e) A means of indicating overcurrent or overload emergency supply generators where these may subjected to overload.
f) Overcurrent protection matched to the generator thermal characteristic for all excited generators (normally portable).
g) Field protection via a field failure relay when generator is likely to run in parallel with another generator or supply.
h) Where portable excited generators are provided, they shall include phase earth fault and reverse power protection to cover the possibility of them ever being run in parallel with other power sources.
i) Protection and control circuits shall be segregated and fused to achieve ideal discrimination.
13.2.4 Special and VT Requirements
The primary rating of line CTs shall be 150% full load current the generator. Neutral shall a primary rating least equal to the neutral
rating. For via a transformer neutral connected CT shall have a 1'1 ratio.
VTs for the AVR and synchronizing shall of two and exclusively
1
1 1
Primary protective fall into two categories, first employs high impedance differential schemes and the second uses overcurrent relays,
normally on incoming circuits or with differentially connected to give partial differential low impedance protection.
1 Differential Protection
High impedance differential protection schemes shall be employed for all 11 kV Switchboards having double bus bars as in 'Primary Substations'. CTs shall be provided in circuit connected to busbar of section with necessary overlaps and the differential relay shall be connected across the pilot such
the summed current through relay.
1 differential Protection
a) The may be provided for all 'Area having single busbar with section(s). unless specified. Single busbars with bus-section breakers shall protected by 3 phase overcurrent and residually connected earth fault IDMT relaying from differentially connected CTs in the incoming and bus-section for each section of
1
DOC. NO. KOC-E-006 Page 34 of REV. 3
b) These partial differential schemes shall overlap at and are of low impedance They for and external faults on outgoing circuits. No instantaneous elements be . The phase fault elements shall be set to pick-up at about 130% of the incoming rating shall time graded with slowest outgoing .... rAta,..".Ar"\
c) Where busbars feed motors of comparable rating to the incomers, two sets phase overcurrent driven the same CTs may be
on partial differential scheme in order to provide high fault current clearance in a reasonable time by using the composite curve referred above.
13.3.4
a) Single busbars with or without bus-section breakers fed or transformers as in 'Plant Substations' shall have 3 and residually connected earth fault IDMT relaying fed from CTs located at the incoming switchgear or the panel. No elements should used. The pick-up of the phase fault elements shall
130% of incoming circuit rating and to co-ordinate downstream relay or
b) Where the busbar a motor of comparable rating to the incomer this leads unacceptable high relay operating times. In such
cases a further overcurrent should provided at of incomer or HV of the incoming transformer and
to form a co-ordination curve with the primary busbar protection overcurrent relay. This second remote relay shall be given a higher than normal pick-up but shall time graded to operate more rapidly under major busbar fault
and Tripping Requirements
All CTs for shall be of the same ratio and matched; primary current rating shall be slightly greater than the full load rating of the largest circuit within the protected zone. function point of the neutral circuit shall as central and equidistant as IJV;:';;:>ll,IlC; to all CTs on a differential relaying scheme.
b) links shall be provided on all CT circuits differential testing.
Busbar protection trips shall be a single dedicated specific hand lock out relay which be arranged trip busbar
overcurrent
set
REV. 3 DOC. NO. KOC-E-006
13.4
1 1
a) protective schemes for transformers of rating 50kVA the following, as applicable:
i)
ii) Buchholz or pressure protection.
iii) fault overcurrent relaying.
iv) Earth fault overcurrent relaying.
v) OillWinding
vi) Differential or circulating schemes.
b) All Transformers fed from a standard switchboard shall be protected with Protection Relays.
c) Transformers supplied from Ring main Units and installed outdoor in the field areas shall be by unless otherwise specified.
d) details on power transformers "KOC Standard for Power Transformers U(KOC-E-005), be
13.4.2 Protection
The shall selected so as not to rupture under magnetising current inrush conditions. They shall normally provided on the HV or primary side of
transformer and may for earth faults on secondary winding. this reason additional earth fault relaying is necessary on the secondary
of the transformer trip the LV breaker. Where transformers are connected in parallel, they shall not be protected by a single set of fuses; instead, appropriately individual primary fuses shall protect transformer.
1 Buchholz or Pressure Protection for Fluid Filled Transformers
a) A Buchholz relay, double-float type, with alarm (gassing) contacts and trip (oil surge) contacts shall be fitted between conservator and tank. A shutoff valve shall be provided between the conservator and relay. The relay shall provided with a test cock and a flexible pipe connection for relay operation. Means shall provided ground level for collection of samples the
b) Where a tank transformer is fitted with a self resetting sudden pressure, spring relief device with trip and alarm contacts, this device also include own dedicated hand flag tripping relay located on respective transformer switchgear to
3
13.4.4 Phase Overcurrent
relays shall fitted on the source side and is required as back-up transformer overcurrent protection even where the transformer is provided with differential protection. It provides normally to pick-up at 125%
should
b) shall include (3) IDMTL and latter be to provide rapid of a source
transformer winding fault. The instantaneous elements shall be designed be immune to DC transients. Where simple instantaneous elements are
provided, shall set to operate at 1.8 times the maximum of the of through fault or current.
c) IDMT element characteristic may of the inverse, very extremely inverse, short or long time but shall selected to
load protection. If is some form overload protection on the load side the transformer, IDMT pick-up may be set much higher than 125% of transformer rating as its function will be to the in the of uncleared side system faults,
d) Directional phase overcurrent may be required if the load busbar has another incomer feeder. provision of two pairs of
fed from CTs on either of transformer, both looking into the transformer avoids need for co-ordination of each relay for faults on both the source and load If the only other infeed is a parallel operated transformer, only the load overcurrent shall
the source one shall remain as a conventional non-directionalised element.
Where motors of comparable to the incoming transformer are source load overcurrent relays shall be set to form a
composite curve. The primary relay is to have a pick-up above motor starting currents operates rapidly high faults; the source relay for transformer overloads but takes a
time than the motor run-up duration before tripping the transformer. transformer is one of a pair of units supplying a comparably
motor the composite curve protection shall duplicating partial differential busbar protection.
1 Fault Overcurrent Relays
a) Earth Overcurrent Relays shall be provided on all transformers of rating 250kVA above, to detect both source side load earth faults. For transformers below 250kVA source side fault shall be provided if the transformer is protected by source side Even with load earth fault relaying is required wherever the
are incapable of detecting secondary faults.
DOC. NO. KOC-E-OOS Page 37 of REV. 3
b) Earth fault relaying may of unit which output current flows and only in zone faults, or of non-unit type which may operate for in or out of zone faults dependent on the earth fault source location.
c) Non-unit type comprising overcurrent elements is and does not always require dedicated CTs. It is therefore preferred for smaller transformers, provided it can satisfactorily graded with ClVTcrn
system fault relaying.
d) The unit form of protection becomes necessary where transformers are banked and high speed and/or discriminatory protection is required. Where transformer windings are not overcurrent cannot operate system earth faults and therefore the essentially non-unit form of protection becomes unitised. In cases the overcurrent relays shall employ instantaneous there will be no need IDMTLo,o~onTc
e) Unit fault protection employing overcurrent instantaneous used to windings.
CTs in the phase, or a single window CT nrH;,rTt:'"
encompassing all three phases may be used.
f) Non-unit earth fault protection employing IDMTL elements shall used protect windings. They be initiated from a CT
located in neutral transformer connection and consequently provide back-up earth fault protection. relay be at 10% of or let through and shall
time with system protection. Instantaneous elements shall not used.
13.4.6 Differential or Circulating Current Schemes
schemes shall include protection for earth faults. Differential each phase output against
lacks sensitivity detecting earth faults on windings near their point, or on delta windings for centrally placed faults. In the case
of impedance earthed neutrals, faults will be to full load transformer or and therefore differential protection will cover even less of transformer star winding.
b) Circulating current schemes rotleCtlOn for phase and
faults of star windings.
c) Differential protection phase shall provided on transformers of 2 MVA rating above. They shall be of percentage biased type to cater for the maximum transformer tap change ratio and shall include a harmonic restraint to avoid maloperation to
'""'<OTrI£'T"'''
differential for earth
inrush
1
1
windings. eTs shall
REV. 3 DOC. NO. KOC-E-006
d) Differential protection eTs shall dedicated for for high impedance restricted earth fault
protection as well as on be connected to counteract the main transformer primary and secondary windings.
e) Restricted earth fault unit protection shall provided to cover for winding faults on all transformers of 1 MVA and above. It shall be provided for all banked below 1 MVA where discriminating earth fault protection is required on star windings.
The relay shall high impedance, instantaneous, low type incorporating a stabilising to provide through fault stability. connections shall compare the resultant current from the three phases with the flowing in the winding neutral. Where differential protection is provided, the eTs in the phase connections may
to drive the restricted fault protection by the use of summation
Indicators
Winding and oil temperature protection shall include dedicated hand tripping relays with alarm and trip indication, which shall be located
Tripping Requirements
a) The trips with transformer shall achieved by using dedicated hand lock out relays, one of which shall trip primary the the secondary circuit breaker.
b) with a transformer primary shall operate primary circuit breaker, and similarly, protection trips
shall operate the for the secondary circuit breaker.
with a transformer
c) following trips should generally operate primary relay:
• IDMT & Instantaneous overcurrent,
... Primary earth fault
... Winding and oil temperature
.. Liquid
... Restricted earth fault (through secondary inter-trip relay)
• Differential protection
Trip)
DOC. NO. KOC-E-·IllIt'ii II Page 39 of 53 REV. 3
d) The following generally operate secondary lockout relay:
.. Restricted earth fault
.. Non-unit (Back-up) earth fault
.. Liquid surge Trip)
.. Winding and oil
.. Differential fid,'fllnn (including partial differential)
.. Directional (in case of parallel operation)
Transformer Protection winding & oil protections, Bucholtz and low oil (alarm only) shall be provided on source end or the secondary switchboard depending upon convenience of operation.
f) Where there is no T""QrlQr system, the primary combined.
In addition to the primary as follows:
tripping schemes, provision through inter-trip
i) The action of tripping the primary circuit breaker secondary circuit breaker a contact from the primary relay in the secondary lockout trip circuit.
trip
secondary
ii)
a provision
13.5
1 1 Load end Switchgear
Where
cables is installed at
are directly connected to plant as transformers
additional cable nrf"ltol"ihf"ln
or without at the remote or load end the protection
by the primary plant or motor protection source end switchgear and
be avoided
systems should cater for
elements shall be set to pick-up
downstream relay. This
40 of 53 3
1 Cables with Switchgear both
These cables should normally inherently selective, the unit which operate for cable, or may be of the overcurrent type which is made time delay co-ordination. earth faults.
13.5.3 Phase Overcurrent
a) Phase overcurrent are less expensive than unit type protection for However the following shall before selection:
i. grading with downstream protection should be possible without increasing the operating back-up protection relay anywhere on to greater than severe fault switchgear is rated for
seconds 3
Ii. fault clearance to overall system worst conceivable
iii. where stability or inherently rapid operating, unit considered.
b) Phase overcurrent relaying be fitted on all three instantaneous element. shall incorporate an
time element should standard inverse time but may to co-ordinate with protection. Instantaneous
with low transient over-reach characteristics are preferred.
c) Normal attracted armature elements may be , provided their setting is to 1.8 times the symmetrical current for remote to cater for DC offset currents.
d) Inverse maximum load condition and to give a 0.4 to
with when co-ordination is with a
currents may flow in either direction, may be required in order
conditions.
relaying of correct fault
system will either not times which are too long
41 of 53 3
f) In the case of parallel systems directional where necessary, shall be at receiving non-directionalised may provided at
relays be applied those ring systems, which Qr'.:ltQ/"I
instances 'closed' and which have intermediate circuit breakers. In
the source end relays not be directionalised ring originates from the same point on the
13.5.4 Fault Overcurrent Relays
Earth fault overcurrent be used all networks grading is without causing unacceptably long earth fault time. They do not operate for earth faults on the side of transformers and therefore only need to co-ordinate with on of transformer which the cable is In order to limit the possibility maloperation should not normally be set to a sensitivity of less than of cable rating.
b) Earth fault overcurrent be rn,,',n"'>r' with phase overcurrent and shall from a connection phase shall also include an inverse time and instantaneous on solidly earthed systems.
c) In cases the distribution system earthfault current is limited by neutral earthing devices, instantaneous elements will not be selective as substantially same fault flows downstream is located. Accordingly earth fault relaying use instantaneous elements on impedance
d) Directionalised fault may be required where currents could flow in either direction. The principal is similar to that covered in overcurrent directionalised relays.
1 Selective or Unit Type
relaying shall provided to protect cables which are controlled by both ends when use of a phase and earth fault overcurrent relaying
satisfactory grading, or leads to maximum tripping prevent disturbance of system.
1 Tripping Requirements
a) protection shall be via hand reset lockout located at circuit breaker on the feeder.
b) Intertripping scheme shall be provided to trip the incomers in of source T",cnor
c) feeders are transformers, reference should be made to 13.4.8 of this for tripping requirements.
DOC. NO. KOC-E-006 Page 42 of 53 REV. 3II
d) Where feeders have switchgear at both ends and either protected by non-directional overcurrent relaying or by circulating current type relaying , the tripping of the source end circuit breaker shall cause the load end circuit breaker to trip. Similarly, the tripping of the load end circuit breaker shall trip the source end circuit breaker.
13.6 Motor Protection
13.6.1 General
Induction motor protection schemes fall into the following main categories:
a) Overload protection.
b) Phase fault protection .
c) Earth fault protection .
d) Unbalanced current protection .
e) Undervoltage protection.
f) Restricted start protection .
g) Miscellaneous protection.
For details on protection of induction motors, "KOC Standard for High Voltage Switchgear and Controlgear" (KOC-E-002) and "KOC Standard for Low Voltage Switchgear" (KOC-E-009) shall be referred.
13.6.2 Overload Protection
a) Single phase motors up to 0.5kW rating shall be provided with built-in thermal protection to IEC 60034-11 or an equivalent national / international standard .
b) Three phase motors between 0.5kW and 15kW rating shall be provided with external thermal overload protection. This type of protection shall be three pole, ambient compensated, incorporating single phase protection .
c) Thermal relays need not be fed from CTs until the motor rating exceeds 15kW.
d) Motors rated between 15kW and 120kW shall be protected by thermal overload relays supplied from CTs.
e) Motors rated above 120kW or those with rated voltages above 1kV shall have two temperature detectors per phase embedded in the stator, unless otherwise specified.
Page 43 of 53 REV. 3
f) motors are protected by circuit breakers, thermal overload may be replaced by motor protection systems or magnetic IDMTL type relays with a long time characteristic provided such motors also include overload protection. These relays shall include three pole for short circuit protection.
g) Wherever the thermal overload has an overrun which precludes providing stalling protection consistent with the motor run-up duration, additional stalling protection shall Stalling protection shall not generally be provided for motors of less than 30kW rating.
Fault ....rn.Tcrnnn13.6.3
a) Short circuit fault protection should normally be provided by the which part of the starter unit. Where circuit breakers are
moulded case or otherwise, phase fault protection provided by instantaneous integral magnetic or by high relay
b) The should be preferably to normal or delayed for some 50 ms to prevent maloperation to high DC
this is not or available, devices shall set to operate at 1.8 times the motor locked Wherever possible the instantaneous relay shall included within the thermal
or IDMTL relay case.
13.6.4 Earth Fault Protection
a) current with definite time-delay protections shall provided for motors 15kW and shall not exceed 5% of full load current or whichever is
b) Alternative a instantaneous overcurrent connected in residual circuit of the line overload / fault protection may be used with prior approval from KOC. However, can only set to operate at 20% of motor full load current. To ensure stability under motor start conditions inclusion of a stabilising resistor mounted in series with the relay may
c) Earth fault protection shall be arranged to trip motor or circuit breaker. In cases where earth fault currents could "",vI".aon the contactor rating, tripping time delay relays or system neutral earthing resistors may used.
1 Unbalanced Protection
a) For motors installed on systems rated at below kV no unbalanced current protection beyond that provided by thermal overload devices in all three is required.
KOC-E-006 3
Motors on systems rated above 3.3 kV shall include negative sequence thermal synthesis relays for protection unbalanced Such relays may part of an overall motor protection covering thermal overload, phasing and phase fault protection.
1 Under-voltage Protection
a) Motors controlled by circuit breakers, or mechanically latched contactors, shall by time delayed under-voltage block restarting of a group of motors in event loss of incoming supply and subsequent restoration. The relay should be to operate at some 70% of normal voltage after a 2 second time and shall of fixed time type with a setting range 0.3 to 3 seconds. Inverse time under-voltage to accomplish same objectives are acceptable and may be used if economically favourable.
controlled by AC operated unlatched contactors shall only include under-voltage relays if sequential load is required at particular under-voltage levels. normal AG contactor provides its own
tripping as contactor drops out in less than 50ms under loss voltage. Under-voltage relaying which forms part shedding schemes should of the instantaneous type with time auxiliary Settings shall recommended in the load shedding study and shall subject to approval by KOG.
13.6,7 Restricted Protection
For some installations it may necessary to restrict the number of starts a machine is subjected to within a period. This is to prevent overheating and subsequent damage or deterioration of the motor insulation or damage to the motor In this case monitoring equipment is fitted within the starter to impose this restriction.
13.6.8 Miscellaneous I-Irr,l'Ot't.
a) temperature detectors embedded in hydrodynamic radial bearings provide protection against bearing should be provided in motors above 1200kW, unless otherwise and shall be a type approved by KOG.
b) Provision vibration monitoring shall be provided for and above 750kW or where vibration may cause significant damage to driven or equipment. The type shall subject to approval by KOC.
C-E-006 Page 45 of 53 3
1 Protection for Downhole Pump Motors
a) The protection for pump motors following as a minimum:
i) Overload.
ii) Earth fault.
iii) Over-tem perature via RTD monitoring.
iv) Undervoltage.
v) Frequent start protection.
b) In addition, it is that machines are running or insufficient In the case of water low shall be installed downhole operation under low conditions. Where rates are specified instrumentation shall be fitted to monitor flow rates trip the machine on low flow rates. provision of motor stall is dependent on duty and the manufacturers
13.7 Shunt Capacitor Bank Protection 131
1 1 capacitor banks shall be provided with protection relays for various functions, including but not limited following:
.. Current
.. Fault
III Voltage
III
.. Undercurrent protection for detection of car>aCIITOr
III Protection to prevent unintentional reconnection of capacitor an no,'''''"]'.o,.. network
.. Lightning I protection
recommended by the of the capacitor the proper and the power factor
Page 46 of REV. 3
14.0
14.1
The minimum requirements for the safe control of power systems / electrical eqUipment are described in this section.
14.2
14.2.1 All electrical power and distribution eqUipment for control plant or at controlling actual eqUipment. Where required, additional control facilities shall provided to enable central or remote control of equipment When alternate control locations exist, padlockable selector shall to ensure control is limited from one location only. Instrumentation, emergency control switches and alarms shall be provided at each location to enable safe control and monitoring.
14.2.2 cabinets for interfacing between the DeS and ESD control systems and the electrical switchgear and the motor shall in substations.
1 Switchgear Controls
switchgear (non-motor cirCUits) shall be operated from the front of switchgear, unless otherwise specified or required special applications.
1 1
1 High-voltage switchgear (non-motor shall operated "from a control in the substation. Switchgear control panels shall comply with KOC
Standard KOC-E-002.
1 position (Iocal/off/remote) selector switch, stayput in each position key lockable, shall be provided on each panel allowing control of
circuit breakers or starters, as required.
14.3.4 Circuit breakers shall be controlled by pistol grip, spring return to neutral type three position switch (open/neutral/close) in the switchgear. Closing the breaker by this switch shall be possible only in the position with selector switch
in local position. However, opening breaker by this switch shall be possible in the service and test positions of the selector switch position (rocal/off/remote).
1 Pushbuttons with exception of motor "stop" push buttons shall be the The "stop" pushbuttons shall red mushroom put,
lockable A minimum one (1) N/O and one (1) N/C contacts shall be provided for each pushbutton.
14.3,6 Facilities for remote indication shall in form of two (2) volt free for each service, all wired out to terminals, These operative in the position.
3O. KOC-E-006 Page 47 of 53
14.3.7 more details on HV & LV Switchgear control, "KOG Standard for High Voltage and Gontrolgear" (KOG-E-002) and "KOG Standard for Low Voltage Switchgear" be
14.4
1 1 Automatic Transfer Schemes shall given attention where is a to obtain a reliability level consistent with two or more sources power supply. Their use shall economically justified compared against other ways of providing duplication of power sources, and shall be limited to installations where there is a need to reduce switchgear short circuit levels either for reasons of or non-availability. All schemes shall only include load transfers that never parallel and sources. Load may use circuit breakers or on-load transfer switches/contactors.
14.4.2 Load be applied to either static loads or induction motor loads or a combination of the two. They not used where synchronous motor loads are supplied. The load transfer shall be arranged so that residual voltage induction motors has to than 25% the source voltage before the transfer is initiated. The rate of calculated and the complete transfer scheme shall be subject to KOG.
voltage decay shall
14.4.3 Induction motors which are controlled by or latched contactors shall include time delayed undervotage relaying. This relaying shall to the controller in typically two (2) seconds or more on voltage dips to below of the with the switchgear supplying these type of induction motor controllers shall be either to re-accelerating the motors if the transfer place within the motor undervolatge tripping or delaying the transfer to be in excess of the motor undervoltage tripping time.
1 it is to restore power to motors controlled by unlatched type of contactors, schemes shall be supplemented by control schemes which restart the motors individually or in groups after a requisite delay.
1 Load transfer a standby generator on a bus bar normally fed from a preferred AG source shall be initiated by time delayed voltage relaying set at volts which shall trip ac source and auto-start the standby generator simultaneously. No transfer delay is required in this case as standby many to run up loaded.
14.4.6 Power system re-acceleration and restart studies shall be carried out to determine most and effective solution for load transfer scheme. And all such studies and conclusions be to approval by KOG.
and Controlgear" (KOG-E-002)
REV. 3 NO. KOC-E-OOS
1
vuu'''u type.
Generator Control requirements to "KOC Standard for Generator (KOG-E-007).
14.S
1 1 Motors or automatically. with manual control facilities "local" the and
installed shall be as follows:
However all motors shall
pushbutton,
b) Stop- pushbutton, red mushroom head, stayput lockable type.
Local/Off/Remote and/or Auto/Manual specified in P&I D.
d) 1 and over.
1 Where only one control position is selected this shall be "local" to the motor. Other manual control positions shall
At a central control room I station.
b) motor as of switchgear.
14.6.3 The "stop" control installed motor be such that will not re-energise
14.6.4 control station with a control shall a "stop" control. In addition, a "stop" control shall provided at switchgear starter panel. controls shall be operable all times and shall be of the hand reset type. Operation of any control shall starting the motor at all control stations.
14.6.5 A "Reset" pushbutton shall included on small motor panels to for overload
14.6.6 Ammeters installed locally on drives shall of the one (1) amp movement, scale, type to IEC 60051, otherwise specified.
14.6.7 Motor starter I switchgear panels in substation switchboards be with ammeters and hours run meters in accordance with the requirements given in "KOC High Voltage
"KOG Standard for Low Voltage S\Allltl"nnQ~
OC. NO. KOC-E
14.7
14.7.1 Relays shall
14.7.2
1
14.7.4
1
1
1
Tripping
Protection
1 normally
14.8
14.8.1
RP.
14.8.2 required.
1 3
1
1
applicable.
cases.
Power
REV. 3 Page
accessible only to particular authorised for setting adjustments. If specified, the relays shall fitted with wired
Resetting shall only be done by an authorised n",r<.:nr
future recurrence.
manual resetting.
circuit conditions, and relays shall be
Motor overloads
The requirement of automatic control or established
Auto/Off/Manual selector switch shall
In the Manual mode, there shall be provision to control the switchgear or remotely from the central control room or plant control room as
setting shall be determined from calculations, shall only be changed by an engineer adequately experienced in this
Each protection relay be individually checked and calibrated, followed by overall protection testing.
All protection relay operations shall be noted in writing before flags are
incidents and connected shall be recorded in detail in an approved manner, together with action to remedy the situation and to avoid
lock out under all overcurrent, and
may to trip on undervoltage or overload reset unless I"\tr'QI"IAIl
shall normally be manually Automatic for small motor driven appliances flexible cables.
131
shunt be as by on study conducted in accordance with clause
provided, automatic control is
Switching on from a position local to capacitor bank is not Remote trip from control room provided in all
Emergency Trip switch should local to the V'""""''"''V' bank.
shall be provided to measure and display various which includes but not limited to the following:
II Current
II Voltage
REV. 3 Page 50 ofDOC. NO. KOC-E
II Power Factor
II I power
II Harmonic
II Data regarding number of ca[)acltor units on etc..
14.8.6 Remote alarm and metering at (central control room I plant room) should as
14.8.7 power quality meters shall providing output signals for remote monitoring and be able to communicate with I DCS.
15.0 ALARMS AND INDICATORS
15.1 substation generation unit shall have an annunciator system provide and warnings of and actual problems. The system shall
differentiate faults and under a and subsequent alarm recognition to provide discrimination A common alarm shall be derived from the annunciator panel for to an centre.
1 Substation alarm annunciator shall display individually from each transformer, I alarm for each incoming or bus section circuit breaker for switchboard status of remote circuit
1 Where remote outputs shall be proVided for DCS systems or Condition Monitoring Systems. All transducers shall give mA outputs with power from the (e.g., DCS)
1 on alarm and indication requirements for electrical equipment, Standards I specifications shall be referred.
16.0 QUALITY ASSURANCE
16.1 Manufacturers and Contractors shall operate a quality system which shall ensure that the requirements of this are achieved.
1 The shall on the ISO 9000 of standards and evidence of the implementation of a system be demonstrated either by accreditation or by the provision of a quality manual for review and approval by KOC.
1 of a vendor's quality system is normally part of pre-qualification and is therefore not detailed in core text of this RP.
D 51 of 53 REV. 3
17.0 DOCUMENTATION
17.1 General
17.1.1 All instructions, drawings, data calculations or any other written information shall be in language. In case of dual one language shall English.
17.1.2 All dimensions, units etc. shall in
The shall be required to submit the proven experience in the of power system design.
17.2
The power study to be submitted to KOC review I approval shall include, but not limited to the following:
a) Load flow
b) Short circuit studies.
c) Stability
d) Motor starting studies.
e) Harmonic analysis studies.
f) 131 Power factor
g) Protective coordination studies including and coordination curves.
I
Units unless otherwise specified
17.1.3 All calculations clearly mention applicable referenced.
17.1 In addition the hard in the approved software.
all documents shall calculations shall
approved software.
17.1.5 All calculations related to power studies and relay settings must have performed by
codes and standards
provided with electronic submitted in the KOC
including the in the field.
DOC. NO. KOC-E-006 Page 52 of 53 REV. 3
ACKNOWLEDGEMENT
This KOC Recommended Practice (Rev.3) has been approved by the Standards Technical Committee (STC) consisting of the following:- 131
Mr. Hamzah Ahmad Standards Team Chairman Mr. Mohd . Emam Insp. & Corr. Team (S&EK) Deputy Chairman Mr. S. Kumar Standards Team Secretary/Member Mr. A. Unnikrishnan Standards Team Member Mr. Mohd. Aslam Imadi Design Team Member Mr. G. Unnikrishnan Design Team Member Mr. N. Ramanathan Major Projects-I, Team IV Member Mr. Daniel Pino Utilities Team Member Mr. Abdul R. AI-Shammari Insp. & Corr. Team (N&WK) Member Mr. Gopal Murthi Opns. Tech. Svcs. (WK) Team Member Mr. Fahad AI-Qattan HSE Systems Team Member Mr. Haithem Abougaith Gen. Projects Team Member Mr. Abdulla AI-Yousef Project Mgmt. Team (NK) Member Mr. Arthur Richard Information Sys. Planning Team Member
The revision (Rev.2) of this Recommended Practice has been circulated to the KOC User Teams for review and the responses were received from the following :
OPNS. GROUP (WEST) AHMADI SERVICES GROUP
Team Leader Opns. Tech . Svcs. Team Leader Utilities
OPNS. GROUP (SOUTH) OPNS. GROUP (EAST)
Team Leader Prod . Opns. Team Leader Opns. Tech. Svcs. Team Leader Opns. Tech. Svcs. Team Leader Maintenance Team Leader Gas Operations
OPNS. GROUP (NORTH) DRILLING SERVICES GROUP
Team Leader Opns. Tech. Svcs. Team Leader Drilling
HSE GROUP MAJOR PROJ. GROUP
Team Leader HSE Systems Team Leader Export Facilities Team Leader Safety
DOC. NO. KOC-E-006 Page 53 of 53 REV. 3 II
Task Force responsible for this Recommended Practice 131
The revision (Rev.3) of this Recommended Practice was entrusted by Standards Technical Committee to the Task Force (TF-EE/07) comprising of the following members:-
Mr. A.Unnikrishnan Standards Team Task Force Leader Tel No. 61633 Mr. Andrew Nayak Gen. Projects Team Member Tel No. 61658 Mr. Hani AI-Awadi OTS (S&EK) Team Member Tel No. 22325 Mr. D. Pattnaik Design Team Member Tel No. 61294 Mr. Rajesh Ramalingam OTS (WK) Team Member Tel No. 20350 Mr. Atholl Robertson PMC - Fluor Member Tel No. 61792 Mr. Sajid Sheikh PMC - AMEC Member Tel No. 61680
