1HSM 9543 23-03en DCB Application Guide Ed3 - 2013-09 - English

8/12/2019 1HSM 9543 23-03en DCB Application Guide Ed3 - 2013-09 - English

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2/602 Introduction | ABB Disconnecting Circuit Breakers


3/60 ABB Disconnecting Circuit Breakers| Introduction 3

Table of contents

Appl icat ion GuideWhat is a Disconnecting Circuit Breaker?

Background and design 8Standards and tests 10

Designing safe substations

Substations without visible gaps 12Earthing switches 13Interlocking in substations 14Interlocking of disconnecting circuit breakers 15

Avai labil ity and reliability

General information 16Disconnecting link 17Improving availability and reliability in a 145 kV substation 18Improving availability and reliability in a 420 kV substation 19

Saving space with DCB

General information 20Space comparison in a 145 kV substation 21Space comparison in a 420 kV substation 22

Environmental benefits

General information 23

LCA study 145 kV 24LCA study 245 kV 25

IntroductionIntroduction 4Reference map 5Product portfolio 6Symbols and abbreviations 7

Appl icat ion Guide (cont inued)LCC (Life Cycle Cost)

General information 26LCC study of a 145 kV single busbar substation 27LCC study of a 420 kV breaker-and-a-half substation 28

Substation design

Single-line diagrams 29Single-busbar configurations 30Double-busbar configurations 32Double-breaker configurations 33Refurbishment and extension 35

Layout examples

Single busbar 145 kV 38Single busbar 420 kV 39Sectionalized single busbar 145 kV 40Sectionalized single busbar 420 kV 41Breaker-and-a-half 145 kV 42Breaker-and-a-half 420 kV 43Double breaker 145 kV 44Double breaker 420 kV 45Ring bus 145 kV 46Ring bus 420 kV 47

Combination 145 kV 48Double breaker 145 kV, extra compact configuration 49Indoor substation ring bus 145 kV 50Indoor substation single bus 145 kV 51

Maintenance operation procedure

Double breaker example 52Sectionalized single busbar example 53

Functional specification

Creating a functional specification 54

www.dcbsubstations.comBuild your own DCB substation 56


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Reference map

DCB installations

Argentina AustraliaBelarusBelgiumBrazilCanadaChinaDenmark Estonia

FinlandGermanyHungaryIcelandIranIraqKazakhstanLithuania

MexicoNew ZealandNigeriaNicaraguaNorwayOmanPeruPolandRomania

RussiaSudanSouth AfricaSpainSwedenUgandaUSA Vietnam

Reference countries


6/606 Introduction | ABB Disconnecting Circuit Breakers

Type DCB LTB 72.5 DCB LTB 145 DCB HPL

170-245

DCB HPL

362 - 420

DCB HPL 550 DCB LTB 72.5

with CT

DCB LTB 145

with CT

Rated voltage, kV 72.5 145 170 - 245 362 - 420 550 72.5 145Rated current, A 3150 3150 4000 4000 4000 3150 3150Circuit breaking current, kA 40 40 50 63 63 40 40

Rated frequency, Hz 50/60 50/60 50/60 50/60 50/60 50/60 50/60

Compact air insulated HV switchgear withDisconnecting Circuit Breakers ABB has a century of experience in building substationsfor high voltage systems. Design and manufacturing of theswitchgear have been constantly refined over the years. Thispermits substations to be built with minimized needs for main-tenance and space, low failure rates, increased safety and lowlife cycle costs. The disconnecting c ircuit breaker is a part ofthis continuous development.

Bracket for current transformers A DCB uses a circuit breaker support structure on which

a earthing switch and current transformer can also bemounted. Furthermore, a complete prefabricated busbarstructure - with the necessary primary electrical connec-tions can be also included.

Line Entrance Module A separate structure called a Line Entrance Module (LEM)is available for supporting apparatus such as voltage trans-formers, surge arresters and earthing switches.

The breaker structure together with an LEM, are normallythe only structures needed to install the HV-apparatus in aswitchgear bay built with a DCB.

Primary switchgear apparatus ABB offers a complete range of primary apparatus for use in Air Insulated Switchgear. Additional information can be foundin the Application and Buyers Guide for each product ac-cording to the table below.

Product Buyers GuideLive Tank Circuit Breakers 1HSM 9543 22-00enOutdoor Instrument Transformers 1HSM 9543 42-00enSurge Arresters 1HSM 9543 12-00en

Appl icat ion Guide

Live Tank Circuit Breakers 1HSM 9543 23-02enOutdoor Instrument Transformers 1HSM 9543 40-00enControlled Switching 1HSM 9543 22-01en

Product portfolio



Symbols and abbreviations

Presentation of DCB in HMI A new graphic symbol for drawings and illustration has beenadopted and introduced in IEC 60617; see the gure below. Although here is no standard for representation of DCB inHMI, we recommend that the following dynamic illustration beused. The dynamic symbols must be able to demonstrate thedifferent operation modes or sequences for the DCB;

AbbreviationsIn this document abbreviations according to the list below are used.

CB Circuit BreakerDCB Disconnecting Circuit BreakerDS Disconnecting SwitchES Earthing Switch/Grounding SwitchSA Surge ArresterCT Current TransformerCVT Capacitor Voltage Transformer

VT Voltage TransformerPI Post InsulatorBB BusbarPT Power Transformer

AIS Air Insulated SwitchgearGIS Gas Insulated SwitchgearSF 6 Sulphur hexafluoride gasOHL Over-head LineCL Cable LineSLD Single Line DiagramLEM Line Entrance ModuleCCC Central Control CabinetMDF/DL Manual Disconnecting Facility/Disconnecting Link IED Intelligent Electronic DeviceMV Medium VoltageHV High Voltage

S/S SubstationLCA Life Cycle AssessmentLCC Life Cycle Cost

SymbolsIn this document the following symbols are used in singleline diagrams.

Circuit breaker

Disconnector

Disconnecting Circuit Breaker

Voltage t ransformer

Current transformer

Surge arrester

Earthing switch

SCADA symbols

Open Closed Open

and

Locked

DCB symbol

according to

IEC 60617

SUBSTATION1 SUBSTATION2

AAD01

AAD01

=AAD01

=AAD01

=-QB001

=-QA001

=-QC001

=-QC002

=-QC001

Unlocked

0 A 0.0 kV 0.0 MW0.0 Mvar

0 A

0.0 kV 0.0 MW0.0 Mvar

0%

0%


8/608 Applic ation Guide | ABB Disconnecting Circuit Breakers

BackgroundDevelopment in circuit breaker technology has led to signifi-cant decreases in maintenance and increases in reliability forcircuit breakers. Maintenance intervals, requiring de-energizingof the primary circuit, of modern SF6 circuit breakers are 15years or more. At the same time, development of open air dis-

connectors has focused on cost reductions by optimizing thematerial used, and has not produced any significant improve-ments in maintenance requirements and reliability. The mainte-nance interval for the main contacts on open-air disconnectorsis about two to six years, differing between different users anddepending on the amount of pollution due to industrial activi-ties and/or natural pollutants such as sand or salt.

Development of circuit breakers and corresponding

reduction of failure and maintenance rates

What is a Disconnecting Circuit Breaker?Background and design

Failure and maintenance rates

Bulk oil breakers

Air blast breakers Disconnectors withopen air contacts

Minimum oil breakers

SF 6 Circuit breakers

1950 2010

420 kV air blast circuit breaker 420 kV oil minimum circuit breaker 420 kV SF 6 circuit breaker

The reliability of c ircuit breakers has increased due to evolu-tion of primary breaking technology, from air blast, oil mini-mum and SF6 dual-pressure circuit breakers into todaysSF6 single-pressure circuit breakers. At the same time, thenumber of breaking units per pole has been reduced, andlive tank circuit breakers up to 300 kV are now available with

one breaking unit per pole. Removal of grading capacitors forlive tank circuit breakers with two breaking units per pole hasfurther simplified the primary circuit and thus decreased thefailure rate. Circuit breakers up to 550 kV are presently avail-able without grading capacitors, enabling the development ofdisconnecting circuit breakers up to this voltage.

Operating mechanisms for circuit breakers have also im-proved. Since going from pneumatic or hydraulic mecha-nisms to spring or motorized type mechanisms, maintenancerequirements and failure rates have decreased.

In the past, the design principle when building substationswas to surround circuit breakers with disconnectors toenable frequent maintenance of the c ircuit breakers. Due tothe large reduction in failure and maintenance rates for circuitbreakers, the disconnecting function is now more appropriatefor maintenance of overhead lines, power transformers, etc .Reduced maintenance of circuit breakers compared to that ofopen air disconnectors, led to the development of the


9/60 ABB Disconnecting Circuit Breakers| Application Guide 9

420 kV SF 6 disconnecting circuit breaker

disconnecting circuit breaker in close collaboration with someof our major customers. The disconnecting circuit breakercombines the switching and disconnecting functions into onedevice, thus reducing the substation footprint and increas-ing availability. The first installation of a disconnecting circuitbreaker was in the year 2000. Disconnecting c ircuit break-ers are now available from 72.5 kV to 550 kV and installed inmore than 30 countries around the world.

DesignIn a disconnecting circuit breaker, the normal interrupter con-tacts also provide the disconnecting function when in the open

position. The contact system is similar to that of a normal circuitbreaker, and there are no extra contacts or linkage systems. Thedisconnecting circuit breaker is equipped with silicone rubberinsulators with hydrophobic properties, i.e. any water on thesurface will form droplets. As a result, they provide excellentperformance in polluted environments and any leakage currentacross the poles in the open position is minimized.

The main advantage of the disconnecting circuit breakercompared to a conventional disconnector is that the electri-cal contacts are enclosed in SF6 gas, as in GIS substations,and thereby protected from the effects of ambient conditions,

including the effects of pollution. The protected environmentprovides improved reliability and prolonged intervals betweende-energization for maintenance of the disconnecting circuitbreaker.

An important aspect of the disconnecting circuit breaker is itsability to provide safe working conditions during maintenanceand repair work in substations. When the disconnecting cir-cuit breaker is used to isolate other equipment, it needs to belocked in the open position in a fail-safe way. This importantaspect has been considered in the design and specificationof the disconnecting circuit breaker. The locking consists of

electrical and mechanical locking of the operating mechanism,as well as mechanical locking of the main linkage system forthe breaker pole.

A disconnecting circuit breaker has to fulfill both applicablecircuit breaker standards and disconnector standards. A specific standard for disconnecting circuit breakers,IEC 62271-108, was issued in 2005.

145 kV disconnecting circuit breaker. An earthing switch is integrated on the

support structure. Contact system similar to that of a normal circuit breaker.


10/6010 Application Guide | ABB Disconnecting Circuit Breakers

What is a Disconnecting Circuit Breaker?Standards and tests

StandardsIEC (International Electrotechnical Commission) has issued afamily of standards, IEC 62271, for high-voltage switchgear. The specific requirements for disconnecting c ircuit breakersare given in IEC 62271-108. In addition, the disconnectingcircuit breaker must fulfill the requirements of both the circuitbreaker standard IEC 62271-100, and relevant parts of thedisconnector standard IEC 62271-102. In turn, IEC 62271-100 and IEC 62271-102 refer extensively to the commonrequirements stipulated in IEC 62271-1.

IEC 62271Part Title

-1 Common specifications-100 High-voltage alternating current circuit breakers

-102 Alternating current disconnectors and earthing switches-108 High-voltage alternating current disconnecting circuit breakers for

rated voltages of 72.5 kV and aboveIEC standards applicable for disconnecting circuit breakers

Important sections in IEC 62271-108 specify how to interlockand secure a disconnecting circuit breaker against unintendedoperation, and also how to verify the dielectric withstand per-formance after an extended period in service.

Indication of position The disconnector standard IEC62271-102 includes therequirements that it shall be possible to know the operatingposition, whether open or closed. Two alternative ways ofmeeting this requirement are given:

The isolating distance or gap is visible

The position of each movable contact ensuring the isolatingdistance or gap is indicated by a reliable visual positionindicating device

For disconnecting circuit breakers the second methods isapplied, with a reliable visual position indicating device. Therigidity of the kinematic chain between the main contacts andthe indicating device is verified by a designated type test.

Type testsBefore a new disconnecting circuit breaker type is released,numerous tests are performed to verify that it complies with

the requirements of the IEC standards. Once the design of thedisconnecting circuit breaker has been finalized, type testsare performed on some of the first manufactured units. Typetests may be performed at the testing facilities of the manu-facturer or at other (independent) laboratories.

A disconnecting circuit breaker must pass the relevant typetests required for both circuit breakers and disconnectors, asstiplulated in IEC 62271-108.

A disconnecting circuit breaker has two different funct ions switching current in its function as a circuit breaker, and

isolation in its function as a disconnector. The main contacts,the hollow insulator in which they are located and the SF6 gassurrounding the contacts may be affected by the mechanicaland electrical switching operations performed. It is thereforeessential to verify that the design fulfills the dielectric with-stand requirements for the isolating distance, applicable for



disconnectors, not only when new but also after an extendedperiod in service. This requirement is verified by the combinedfunction test, specified in IEC 62271-108. In this test, thedielectric withstand capability across the isolating distance isdemonstrated after a mechanical operation test, as well asafter a specified short-circuit test duty.

The combined function test consists of one part limited tothe mechanical function, and one part limited to the electricalfunction. These two parts may be performed either separatelyor together in one sequence. The mechanical combined func-tion test is performed with the appropriate number of opera-

tions for mechanical endurance class M1 or M2.

Mechanical combinedfunction tests

Mechanical operationtest according toIEC 62271-100

(M1 or M2)

Alternative testmethod limited to

mechanical wear only(M1 or M2)

Dielectric tests acrossthe isolating distance;test values according

to IEC 62271-102

Short-circuit combinedfunction tests

Short circuit testduty T100s according

to IEC 62271-100

Alternative test producingthe same electrical wear

Dielectric tests acrossthe isolating distance;test values according

to IEC 62271-102

The two parts of the combined function test

Routine testsRoutine tests are performed on each disconnecting circuit break-er manufactured to reveal any faults in materials or assembly.

Quality control ABB AB, High Voltage Products in Ludvika has an advancedquality management system for development, design, manu-facturing, testing, sales and after sa les service, as well as forenvironmental standards, and is certified by Bureau Veritas forISO 9001 and ISO 14001.



Designing safe substationsSubstations without visible gaps

Substations without visible gapsOver the years the visible gap provided by disconnectors hasbeen used as an indication of safety when working in AISsubstations. In GIS substations, and with all medium voltageswitchgear, there was no need for a visible gap from the be-ginning. A reliable indication device (assured by IEC tests) hasbeen used instead for disconnectors and earthing switches.

A visible gap itse lf does not provide sufficient safety to startwork on high voltage equipment. Not until an earth is con-nected, can work on high voltage equipment be carried out.

When the disconnecting circuit breaker is locked in its openposition, it has the same function and dielectric withstand asa traditional disconnector. The safety needed to start workon high voltage equipment is still achieved when thevisibleearthing switch is closed.

To further enhance safety, it is always recommended toconduct all operations remotely. Substations with disconnect-ing circuit breakers utilize remotely operated visible earthingswitches for safety measures, rather than the visible gap andportable earthing switches used in conventional solutions.

After a sequence of operations (open DCBs, lock DCBs, closeearthing switches), the substation personnel can enter thealready earthed switchyard to padlock all equipment beforethe next work permit is submitted.

Safety distancesIEC and other standards prescribe distances in switchgear. Those standard values can sometimes be raised by thecustomer due to local conditions.

Special attention must be paid to the distance to nearestlive part, also called section clearance. This distance mustbe established between all live parts and the location in theswitchgear where work will be performed.

The table shows example values that must always be coordi-

nated with the demands of the actual installation.

Example values for distances (mm)

72.5 kV 145 kV 245 kV 420 kV

Lowest insulator base to earth 2250 2250 2250 2250Earth and lowest live part 3000 3770 4780 5480Between phases 630 1300 2100 4200Phase to earth 630 1300 2100 3400 Transport way profile 700 1520 2350 3230 To nearest l ive part 3000 3270 4280 4980



Earthing switches

Where to place earthing switchesDepending on the conguration and voltage level in the substa-tion, the position of the earthing switches differs. Regardlessof substation conguration, it is recommended that an earthingswitch be placed on each busbar in the substation.

For single-busbar applications, the earthing switch is normallyinstalled on the same structure as the DCB, and the fixed con-tact of the earthing switch is installed on the lower connectionflange on the disconnecting circuit breaker (see Figure 1).

Figure 1

Single bus

Figure 2

Double breaker

Figure 3

Breaker-and-a-half

In systems where the object is fed from two directions, e.g.double-breaker or breaker-and-a-half systems, it is morepractical to use a freestanding earthing switch at the commonconnection point to the object (see Figures 2 and 3). This isbecause the purpose of the earthing switch is to earth theconnected object (line/transformer, etc.) and not the circuitbreaker or other high voltage equipment.Remote operation of the earthing switches is recommendedand a motorized earthing switch should thus be used.



The operation sequence allowed in the substation when ut iliz-ing disconnecting circuit breakers is according to the sameprinciples as for a conventional substation. See the examplebelow for assurance that an object is not unintentionally earthed.

Once mechanical locking of disconnecting circuit breakershas been carried out, the output signal disconnecting circuitbreaker locked in open position is sent to the interlocking

system. As soon as all other paths feeding the object to beearthed are also disconnected, and the primary voltage atthis point is zero (checked through voltage transformer toensure that the remote line end is open), the interlocking sys-tem will produce a release signal that enables the earthingswitch to be closed. Normal safety actions, such as padlock-ing and labeling of the closed earthing switch, are carried outin the usual way.

Equipment level

Relay and protection level

Locked inopen position

Locked inopen position

Zerovoltage

andfunctioning

Earthing switch can be closed

Designing safe substationsInterlocking in substation


15/60



Availability and reliabilityGeneral information

Availability and reliabili tyIn todays electrical transmission and distribution grids, thebiggest concern is in dealing with outages, thus maximizingthe capability to transmit power to end-customers. Outagesare normally due to maintenance but could also be caused byrepair work after failures.

The way to maximize the power flow is to use equipment inthe substation with low maintenance requirements, as well assuitable substation configurations.

Another major obstacle is in avoiding any blackouts for power

consumers, or loss of connection to generating power sta-tions. Such events are entirely related to unplanned activitiesdue to a failure of some kind. The quality of a certain sub-station in this respect is often expressed as reliability, or howfailure tolerant it may be. Reliability, such as for an outgoingbay in a substation, is the probability of failure-free powersupply at that point during a specified period of time. Unreli-ability may be expressed as the expected number of interrup-tions per year.

Improved availability with DCBThe availability of an outgoing bay in a substation, is the

fraction of time that electrical power is available at that point.

A typical power path through a substation can be divided intothree main parts: line, power transformer and switchgear.Lines and power transformers have relatively high maintenancerequirements. They constitute the chief cause for maintenanceoutages in substations supplied by single radial lines, or withonly a single transformer. In such cases, maintenance ofswitchgear is of secondary importance. On the contrary, ifpower can be supplied from more than one direction and thesubstation is equipped with parallel transformers, the overallunavailability of the substation, due to maintenance, may be

directly related to the switchgear and the substation configu-ration. Decisive factors are then the HV equipment used, aswell as the arrangement (single-line diagram) of the substation.

The chief reason for unavailability of a certain part of a sub-station is maintenance. Unavailability, i.e. the fraction of timethat electric power is not available, is normally expressed inhours per year.

In the past, circuit breakers were mechanically and electricallycomplex and therefore required considerable maintenance. The focus was on how to isolate the circuit breaker formaintenance and keeping the other parts of the substationin service. The substations were accordingly built with circuitbreakers surrounded by several disconnectors enable circuitbreaker to be isolated and maintained. Now when modern

circuit breakers require less maintenance than conventionaldisconnectors, substation availability is improved whenconventional disconnectors are removed and disconnectingcircuit breakers are used.

Improved reliability with DCBReliability is the probability of failure-free power supply at acertain point during a specified period of time.

From the above statement it is clear that only failure frequency,not maintenance in the substation, is taken into considerationwhen looking at reliability. Failure or unreliability of any equip-

ment in the substation is usually considered as the most cost-ly substation event, as it cannot be planned for in advance.

The concept of the disconnecting circuit breaker is to eliminateconventional disconnectors and simplify substation design. This minimizes the probability of a failure in a substation.Substations equipped with disconnecting circuit breakers canbe built in a more simplified arrangement than substa tionswith conventional equipment and still achieve higher reliability.

For important substations, it may not be acceptable from asystem security perspective to risk losing the whole substa-

tion in the event of a primary fault. To make a substation im-mune against busbar faults and to minimize the disturbancein the event of a primary fault, a breaker-and-a-half or doublebreaker arrangement is commonly used.



Disconnecting link

Disconnecting link Sometimes it can be practical to disconnect a unit from thebusbar or the line during maintenance or repair. This is nota special demand for solutions with disconnecting circuitbreakers, but it has been emphasized as a tool to furtherincrease availability.

A disconnecting link, is a point in the substation prepared forfast opening of the primary connection, between disconnectorfor example, or in this case, a disconnecting circuit breakerand the busbar.

When a disconnecting circuit breaker is isolated in this way,the other parts of the substation may be re-energized duringwork on the disconnecting circuit breaker itself. This increasesthe overall availability of the substation.

The disconnecting link consists of standard clamps and awire or tube. The connection points for the disconnecting linkare arranged so that when the disconnecting link is removed,there are necessary safety distances between the isolatedequipment and the busbar or line. The distance shall fulfillspecific requirements in the form of section clearance. Thefigures illustrate with dots, where section clearance is applied

in different substation arrangements.

Double breaker

Breaker-and-a-half

Removal and reconnection of a disconnecting link in a 420kV substation is estimated to take less than one hour foreach operation.

An important factor is that a disconnecting l ink is not to becompared with a disconnector since it is maintenance freeand is intended to be used only on rare occasions, typicallyonce or twice during the lifetime of the substation.

Disconnecting link Open

A disconnec ting link mounted

on the busbar

Disconnecting link Closed

Disconnecting link



Availability and reliabilityImproving availability and reliability in a 145 kV substation

As an example , a comparison is made between a conven-

tional double busbar substation versus a sect ionalized singlebusbar arrangement, equipped with disconnecting circuitbreakers and disconnecting links. As the conventional doublebus single breaker and DCB sectionalized single breaker areconnected in the same way during normal service condi-tions, and busbar switching is typically only carried out dueto scheduled disconnector maintenance, this is a very goodcomparison to make. Assumed maintenance intervals arefive years for open air disconnectors and 15 years for circuitbreakers and disconnecting circuit breakers.

The comparison involves:

4 Incoming OH lines2 Power transformers1 Bus coupler

Introduction of the disconnecting circuit breakers reduces the

average unavailability due to maintenance for a single bay inthe substation from 3.07 to 1.2 hours per year. The compari-son proves that the reliability of a single bay in the substationwill increase, thus decreasing the failure outage duration from0.17 to 0.15 hours per year.

Maintenance outage 145 kV Failure outage 145 kV

Convent ional double bus si ngle breaker substat ion wi th di sconnector s Se ctional ized singl e bus s ubstati on wit h

disconnecting circuit breaker


Disconnecting link, to be used during maintenance or in a rarecase of failure of disconnecting circuit breaker

0.0

2.5

1.2

5.0

Circuit breakersand

disconnectors

Disconnectingcircuit breakers

Outage duration (hours/year)

3.07

0.0

0.1

0.3

Circuit breakersand

disconnectors

Disconnectingcircuit breakers

Outage duration (hours/year)

0.17 0.150.2


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Saving space with DCBGeneral information

The development of the disconnecting circuit breaker has led to the integration of conventional circuit breakers anddisconnectors into a single unit. The benefit of combining the two functions is that it enables the required space for thesubstation to be significantly reduced.

Width difference of a substation usingdisconnecting circuit breakers The figures above provide an approximation of the spacerequirement for one bay in single-busbar arrangements usingconventional equipment (Figure 4a) and disconnecting circuit

breakers (Figures 4b and 4c).

Disconnecting circuit breakers can be used in most traditionalsubstation configurations, and directly replace conventional

CB/DS arrangements, thus minimizing the area needed for thesubstation.

Conventional substations normally require more space be-tween the phases in the bays compared to disconnecting

circuit breaker substation. This is due to movement of thedisconnector arms.In the case of a 420 kV breaker-and-a-half substation, thereduction in width is approximately 17%.

Figure 4a A conventional bay with circuit breakers and disconnectors

Figure 4b The disconnecting circuit breaker solution reduces the bay footprint by approximately 30%

Figure 4c The disconnecting circuit breaker with the current transformer on

brackets and busbar on top reduces bay footprint by approximately 75%

100%

70%

25%



Comparing the space requirements for a 145 kV substat ionusing the same example from the chapter Availability andreliability, the following space reduction is achieved. See thefigures below for single-line diagrams with layout drawings.

It can be concluded that by building a 145 kV substationwith disconnecting circuit breakers instead of conventionalequipment, the space requirements for the outdoor switch-

Space comparison in a 145 kV substation

Space requirements for a conventional double busbar substation with circuit breakers and disconnectors

Space requirements for a substation with disconnecting circuit breakers

50 m

49 m

77 m

54 m

yard is reduced from 4,200 m2

to 2,500 m2

, which isa reduction of more than 40%. A disconnecting circuitbreaker solution can also facilitate extension of thesubstation with one or two bays on either side of thetransformer without using more space than a conven-tional solution with four overhead lines and two powertransformers.


Disconnecting link, to be used during maintenance or in a rarecase of failure of disconnecting circuit breaker



Saving space with DCBSpace comparison in a 420 kV substation

Comparing the space requirements for a 420 kV substationusing the same example from the chapter Availability andreliability, the following space reduction is achieved. See thefigures below for single-line diagrams with layout drawings.

Space requirements for a conventional substation with circuit breakers and disconnectors

Space requirements for a substation with disconnecting circuit breakers (Space saving 46%)

DS DSCT

VT

CB

VT

DS DSCT CB DSDS CT CB

DS DSCT CB DS DSCT CB DSDS CT CB

DS DSCT CB DS DSCT CB DSDS CT CB

160 m

72 m

DCB CT

VT VT

DCB CT DCBCT

DCB CT DCB CT DCBCT

DCB CT DCB CT DCBCT

103 m

60 m

The conclusion when implementing a disconnecting circuitbreaker in a 420 kV breaker-and-a-half arrangement is that aspace reduction is achieved from 11,500 m2 to 6,200 m2, whichis approximately 50% when compared to a conventional solution.

Disconnecting Circuit Breaker Disconnecting link, to be used during maintenance or in a rarecase of failure of disconnecting circuit breaker



Environmental benefitsGeneral information

ABB has a clear commitment to decreasing the environmentalimpact caused by designed and manufactured systems andapparatus. We thus hold certification in compliance with envi-ronmental management systems ISO 14001 and ISO 14025.Minimized environmental impact during the development ofthe disconnecting circuit breaker has consequently been animportant consideration. Life cycle assessment (LCA) pro-cedures were applied to optimize the design, and checklistsused to identify potential sustainability risks.

Use of disconnecting circuit breakers reduces the land arearequired for an air insulated substation and reduces material

usage. The secondary system in the substation is simplifiedwhen interlocking functions between conventional disconnec-tors and circuit breakers are no longer required. In addition,power losses related to conventional disconnectors are avoided.

Use of raw materials As the number of primary apparatus is decreased comparedto conventional solutions, the total use of raw materials issignificantly reduced. This refers to all kinds of material thatare normally used in switchgear apparatus, such as steel,aluminum, copper, plastic, oil, etc.

Number of foundations use of concrete The number of foundations required for substations withdisconnecting circuit breakers is significantly lower thanfor conventional switchgear as the number of primary ap-paratus is less. In addition, apparatus can be mounted onshared structures, which further decreases the number offoundations. Typically, a substation with disconnecting circuitbreakers needs only half or less of the number of foundationscompared to a conventional substation.

SF 6 gasDisconnecting circuit breakers utilize SF6 (sulfur hexauoride)

gas for insulation and arc quenching purposes in the same wayas normal circuit breakers. However, SF6 contributes to thegreenhouse effect and must therefore be handled with caution.

The live tank design of the disconnecting circuit breaker mini-mizes the amount of gas used compared to alternative tech-nologies. Any gas leakage during operation is also minimizedby means of sealing systems using double O-rings for sta tic

seals and double X-rings for dynamic seals. High and lowtemperature tests have shown that the relative SF6 leakagerate stays well below the strict IEC requirement of 0.5% peryear for closed pressure systems, even under severe environ-mental conditions. The low gas volume together with the lowleakage rate subsequently leads to minimized SF6 emissionsinto the atmosphere. Furthermore, ABB has well-documentedroutines for handling SF6, from production of the apparatus toremoving it from service.

As illustra ted by the examples on the following pages of lifecycle assessment (LCA) calculations, the equivalent global

warming potential (amount of CO2 released into the atmos-phere) is dominated by electric power losses during servicelife and not by SF6 leakage.

Replacing SF 6 gas with CO 2 gas Another groundbreaking technology is arc quenching by usingCO2 instead of SF6, which completely removes the use of SF6in disconnecting circuit breakers up to 84 kV.

The graph below shows a comparison of life cycle environmen-tal impact of ABBs new LTA CO2 circuit breaker with ABBsLTB SF6 circuit breaker considering service life of 30 years. The

points below elaborate how the LTA technology has evolved forreducing environment impact in each of the three life cyclephases (design and manufacturing, service and scrapping).

SF 6 losses: Service phase

Auxiliary circuit: Service phase

Primary circuit losses: Service phase

Design & manufacturing andscrapping phase

0 %

20 %

40 %

80 %

60 %

100 %

120 %

SF 6 circuit breaker(LTB 72D1/B with BLK 222 spring drive)

CO 2 circuit breaker(LTA 72D1/B with MSD1 spring drive)

Comparative CO 2 equivalent GWP impact in 30 year service life



Environmental benefitsLCA study, 145 kV

LCA study for 145 kV disconnectingcircuit breaker with earthing switch An LCA study was made for a 145 kV disconnecting circuitbreaker, including the operating mechanism, earthing switchand support structure. The study took into consideration theenvironmental impact of the entire life cycle, and fulfilled therequirements of ISO 14040.It was based on the following assumptions:

40 year life span Electrical losses for 50% of rated normal current, i.e.

1575 A per phase

Three-pole operated disconnecting c ircuit breaker, resis-tance 32 /pole, heater 70 W continuous, plus 70 Wthermostat controlled 50% of time

Several different environmental impact categories may beconsidered in LCA studies, such as acidification, ozone deple-tion and global warming. In the present case , evaluation wasmade with regard to the global warming potential (GWP). Thisis generally the dominating impact category for products con-suming energy during their service life. The result is expressedin kg CO2 equivalents.

The impact from electric energy consumption is based on a mixof power generation systems relevant for the OECD countries,and considers the LCA perspective: 0.6265 kg CO2 per kWh.

As shown in the figure, electric energy consumption dur-ing the usage phase contributes most to the global warmingpotential. Resistive losses in the main circuit are responsible

for 70% of this energy consumption. The rest is shared by thethermostat-controlled heater (10%) and the anti-condensationheater (20%) in the operating mechanism. It was assumedthat the thermostat controlled heater was connected duringhalf of the usage phase.

The contribution during the usage phase related to SF6 leak-age into the atmosphere is less than 10% of the total. Thisis a result of the small gas volume and low relative leakagerate of the live tank design. The contribution was calculatedassuming a relative SF6 leakage rate of 0.1% per year, whichis typical for this type of disconnecting circuit breaker. At

end-of-life, it was assumed that 1% of the gas is lost, whilethe rest is recycled.

-10000 10000 30000 50000 70000 90000kg CO equivalents2

Energy and material SF 6

End-of-life

Manufacture

Use



LCA study, 245 kV

LCA study of three 245 kV substation alternativesLCA assessment was carried out for three different types of 245kV substations. All three variants were dimensioned to fulll theconditions of an actuall substation at a specic site:

Five overhead lines, with fixed positions One power transformer with fixed position and connecting to

an adjacent 420 kV substation

Conventional AIS substation (Type 1)Double busbar conventional AIS substation, according to thefollowing single-line diagram:

Indoor GIS substation (Type 2)

Indoor GIS substation, with the same-single line diagram as aconventional AIS substation. In the LCA, the required externalconnections from the GIS to the actual positions of the powertransformer and OH lines were included. These external AISconnections added up to a total of 240 m. The following figureshows, as an example, the situation for the transformer bay:

Gasinsulated

switchgear

Gas insulated switchgear with external AIS connections

AIS substation with disconnecting circuit breakers (Type 3) This substation had a double-breaker conguration, which pro-vides even higher exibility and reliability than a double-busbarconguration.

The number of disconnecting circuit breakers in this congurationis 12, as compared to 7 circuit breakers in the double-busbarsingle-breaker congurations.

The main input parameters for the LCA analysis were:

30 year lifetime SF6 leakage rate 0.1% per year, for both AIS and GIS Two load current scenarios were used:

Scenario A: 80% of time at 25% of 3150 A, and 20% oftime at 40% of 3150 A.

Scenario B: 80% of time at 40% of 3150 A, and 20% oftime at 50% of 3150 A.

The impact from electric energy consumption is based on amix of power generation systems relevant for 25 EuropeanUnion (EU) countries, and considers the LCA perspective:0.5773 kg CO2 per kWh.

The losses in the power transformer were not included The main results of the study the equivalent CO2 emissions are shown in the following figure:

The major conclusions of the study are:

The lowest environmental impact is caused by the AISsubstation with disconnecting circuit breakers (Type 3)

The largest part of the environmental impact is caused bythe electrical losses during service life

It should be kept clearly in mind that the results depend to a highdegree on the actual conditions, line lengths, etc in the

substation. A different situation may well lead to different results.

100000 20000 30000 40000 50000

AIS,DCB

AIS

GIS

Material Uti lization SF6

AIS,DCB

AIS

GIS

SCENARIO B

SCENARIO A



Life Cycle Cost (LCC)General information

The high voltage equipment in a substation will have acertain up-front cost, followed by a number of addi-tional costs, which gradually build up during the lifetimeof the equipment. In life cycle cost (LCC) calculations allthese cost elements are considered, in order to give arelevant picture of the total lifetime cost.Such LCC calculations can be used as a powerful toolwhen comparing different substation solutions as early asthe planning stage.

The following cost elements should be included in an LCCcalculation for the high voltage equipment in a substation:

Initial costWhen the LCC analysis is directly focused on the HV equip-ment, the initial cost consists of the purchase cost for thisequipment and associated costs for the foundations neededfor erection of the equipment. Installation and commissioningcosts should also be included.

It may also be feasible to use a wider perspective and includefurther cost elements, such as design and planning, projectmanagement, civil works for the substation, busbars andprimary connections between the HV equipment, and also

auxiliary cabling. Such costs will generally be lower for sub-station solutions with disconnecting circuit breakers than forconventional solutions due to less space and less equipmentbeing required, as well as due to the use of partly predesignedsolutions.

Maintenance costs The maintenance cost during the life time of the equipment willdepend on the maintenance intervals and on the maintenancetime. Both visual inspections and scheduled maintenanceshould be included. The cost of complete overhaul of theequipment, after many years in service may also be included,

as well as distance costs related to travel to the site .

The maintenance cost will depend on the hourly rates of theservice staff. For simplified calculations, it may be assumedthat current transformers, voltage transformers and surgearresters are maintenance free.

Repair costs The repair costs will depend on the failure rates of the equip-ment, and on the repair times and cost of spare parts. Typicalfailure rates may be taken from statistics published by CIGR,for example. Distance costs, related to travel to the site,should be included. The repair costs will depend on the hourlyrates of the service staff, rental costs of cranes etc.

Costs of electrical losses The main current leads to electrical losses both in the highvoltage equipment and in the connections between them. The losses depend on the magnitude of the current, and asuitable, average current value should be used for the calcula-tion. When different substation configurations are compared,the interconnections included in the comparison should bechosen in the same way, such as based on the length of adiameter in a breaker-and-a-half configuration. In addition tothe main current losses, the energy consumption of heaters inthe operating mechanisms of the circuit breakers, disconnect-

ing circuit breakers and disconnectors should be included.

The maintenance costs, repair costs and costs of electricallosses will all build up gradually during the service life of theequipment. These costs should therefore be recalculated topresent values using a suitable interest rate.

Two examples of LCC calculations are shown here, makingcomparisons between substation solutions with conventionalcircuit breakers and disconnectors, and with disconnectingcircuit breakers.



The figure shows the costs as present values, based on a 5%annual interest rate. The initial cost (purchase plus installationcosts) of the two alternatives is more or less equal, while thetotal cost is higher for the conventional a lternative. This is dueto considerably higher costs for both maintenance and electri-cal losses.

LCC comparison; Disconnecting circuit breaker

versus conventional solution, single-bay 145 kV

0

10000

20000

30000

4000050000

60000

70000

80000

90000

100000

Disconnecting circuitbreaker solution

Conventional circuitbreaker solution

Initial cost Maintenance and repair Electrical losses Total

EUR

The life cycle cost (LCC) is calculated for a single 145 kV dis-connecting circuit breaker, compared to an arrangement witha conventional circuit breaker surrounded by two disconnec-tors. For the conventional arrangement, the connections be-tween the disconnectors and the circuit breaker are included(blue section in the figure).

Disconnecting circuit breaker Circuit breaker with

two disconnectors

Realistic costs are assumed for purchase of equipment, instal-lation, maintenance and repair. A 30-year time span is used.Complete revision of the equipment is included, at the end ofthe time span. The electric losses are calculated with currentof 1575 A, which is 50% of the rated current. Electrical lossesin the heaters of the operating mechanisms are included. Thecost of the electrical losses is based on 0.03 EUR per kWh.

LCC study of 145 kV single busbar substation



The figure shows the costs as present values, based on a5% annual interest rate. The initial cost (purchase plus instal-lation costs) for the alternative with disconnecting circuitbreakers is slightly lower than for the conventional alternativewith circuit breakers and disconnectors. The total cost isalso lower, due to lower maintenance and repair costs, andalso lower cost of electrical losses for the alternative withdisconnecting circuit breakers.

LCC comparison: Disconnecting Circuit Breaker

versus conventional solution, 420 kV

The life cycle cost is calculated for the high voltage equipmentof a 420 kV substation with a breaker-and-a-half configura-tion, and four diameters. Two alternat ives are compared, onewith disconnecting circuit breakers, and one with conventionalcircuit breakers and disconnectors. The costs associated withall high voltage equipment regarding the feeders and diam-eters are included, i.e. circuit breakers or disconnect ing circuitbreakers, disconnectors, earthing switches, current and volt-age transformers, and surge arresters. As can be seen in thefigures, it has been assumed that there are no disconnectorson the feeders. High voltage equipment directly connectedto the busbars is not included. Connecting conductors in the

diameters and between HV equipment connected to the feed-ers are included (blue and red sect ions in the figures).

Realistic costs are assumed for purchase of equipment,installation, maintenance and repair. A 30-year time span isused. Complete overhaul of the equipment is included, atthe end of the time span. The electric losses are calculatedwith current of 2000 A, which is 50% of the rated current(flowing in the blue section of the feeders and diameters).Electric losses in the heaters of the operating mechanismsare included. The cost of the electrical losses are based on0.05 EUR per kWh.

0

500000

1000000

1500000

2000000

2500000

3000000

DisconnectingCircuit Breaker

ConventionalCircuit Breaker

Initial cost Maintenance and repair Electrical losses Total

EUR

Life Cycle Cost (LCC)LCC study of 420 kV breaker-and-a-half substation

Arrangement with conven tional circu it breakers and disconnectors Arrangement with disconnecti ng ci rcuit breakers

Note: Additional savings in buying and preparing the land and civil works arenot included in the LCC comparison.



Substation designSingle-line diagrams

Different substation configurationsWhen designing a new substation, a number of consider-ations need to be taken into account. One of those is theconfiguration illustrated by the single-line diagram (SLD).When preparing single line diagrams, the main goal is tocreate a solution suitable for the specific requirements of thesubstation. Many factors such as the expected load, safetyrequirements, substation budget, surrounding power network,effects of power loss, availability and reliability requirements,etc. influence the final decision.

Single-breaker configurations

Substations designed with only a single circuit breaker perobject and several surrounding disconnectors are consideredas maintenance-focused substations. Common for these arethat the circuit breakers and sometimes disconnectors caneasily be isolated without affecting the power ow in the busbarand when bypass disconnectors or a transfer bus is used, notthe actual load on connected objects. Double-busbar singlecircuit breaker congurations are commonly used. Nonethe-less, the load is divided in the substation as with a sectional-ized single busbar and switching in the substation is mainlyperformed when busbar-adjacent disconnector maintenance iscarried out. In such configurations, a line fault in combination

with protection failure or a no-trip event on a circuit breakerwould result in a loss of at least half the substation.

Examples of conventional and disconnecting circuit breakersingle line diagrams for single circuit breaker configurationsare shown on the following pages.

As stated for the above solutions with single-busbar congura-tion, maintenance of the busbar adjacent disconnectors takesthe section or the entire substation out of service. To eliminatethis problem double busbars were introduced, i.e. the main rea-son for double busbar systems is to allow disconnector mainte-

nance without affecting the other objects in the substation.

Double-breaker configurationsSubstations with the object of interest connected to twocircuit breakers are considered to be failure- and maintenancefocused substations. For example, a line failure in combinationwith a protection failure or no-trip event on a c ircuit breakerwould only affect the object of interest and maximum oneother object. That is the reason why these types of configura-tions are most commonly used in transmission grids and in-dustries with very high availability and reliability requirements. Another advantage of these configurations with two simulta-neous feeder paths is that the object can be easily restored toservice after a failure or maintenance of relevant equipment.

New possibilities with disconnecting circuit breakers As shown earlier in the chapter Availability and reliability,modern SF6 circuit breakers offer better maintenance andfailure performance than disconnectors. That means thatthe traditional way of building substations with many busbarsystems and disconnectors decreases availability instead ofincreasing it. Taking only the above into consideration, thebest way to increase availability is to eliminate all disconnec-tors and only use circuit breakers. However, due to safetyaspects, a disconnector function is necessary, which makesthe disconnecting circuit breaker necessary for designing

disconnector-free substations.

The disconnecting circuit breaker is suitable for use insubstation configurations such as:

Single busbar Sectionalized single busbar

Double breaker Ring bus 1 circuit breaker Combination configurations

If a double-busbar or transfer bus system is under consid-eration, it can preferably be replaced by a double-busbar,double-breaker system. In the following section some exam-ples of the above will be illustrated.



Substation designSingle-busbar configurations

Single busbarSingle busbar is the simplest configuration and is

preferably used in smaller substations with singleline feed and lower voltages. In the single busbarconfiguration, all objects connect to the same busbar,making the substation small but vulnerable to failures andmaintenance. If maintenance is required on any of thebusbar-adjacent equipment, the entire substation must betaken out of service.

ConventionalWith the conventional single busbar configuration, busbardisconnectors enable circuit breaker maintenance without de-energizing the busbar. Nonetheless maintenance of busbar-adjacent disconnectors takes the busbar out of service. Asthe busbar-adjacent disconnector presently requires moremaintenance than conventional circuit breakers, the busbaravailability is decreased compared to a disconnecting circuitbreaker solution.

Disconnecting Circuit Breaker In the disconnecting circuit breaker solution, all disconnectorsare removed; hence the maintenance frequency for the sub-station is decreased from approximately every five years to

every fifteen years. Simplified interlocking schemes togetherwith a smaller substation footprint and lower maintenancerequirements will provide cost benefits in comparison to theconventional solution.

Single busbar with bypass disconnectorIn a conguration with a single busbar and bypass

disconnector, objects stay connected as in the single busbarconguration. The bypass disconnector was introduced toenable circuit breaker maintenance without losing the line.When the circuit breaker is in need of maintenance the linecan be connected through the bypass disconnector to thebusbar, hence the line will be connected without a breaker.If a line failure should occur in this situation, the entiresubstation would be taken out of service.

Conventional Todays bypass disconnectors require more maintenancethan the circuit breakers they were supposed to eliminatemaintenance outage from, hence line availability will decreasecompared to a single busbar configuration. The addedbypass disconnector will also deenergize the busbar, andhence the entire substation, during required maintenance.

Disconnecting Circuit Breaker The solution with disconnecting circuit breakers and bypassdisconnectors is not applicable since no disconnectors areused. It is instead recommended to use a single busbar or

sectionalized single busbar with disconnecting circuit breakersto improve substation availability.



Single busbar with transfer busbarIn the configuration with a single busbar and transfer

busbar, the objects stay connected as in the single-busbar configuration. The single busbar with transferbusbar was introduced to enable circuit breakermaintenance without losing the object. During circuitbreaker maintenance, the bus-coupler breaker is usedas the line breaker for the bay where circuit breakermaintenance is performed. This solution has lost itspurpose today because transfer disconnectors requiremore maintenance than circuit breakers, hence theobjects availability will decrease compared to a single-busbar configuration.

Conventional The advantage of a single busbar with transfer bus comparedto a single busbar with a bypass disconnector is that main-tenance of the transfer disconnector will not affect the mainbusbar as the by-pass disconnector does. Nonetheless, asmentioned in the section above, a pure single-busbar solutionwill perform better than a single busbar with a transfer busbar.

Disconnecting Circuit Breaker The solution with disconnecting circuit breakers and a trans-fer busbar is not applicable. It is instead recommended to usea single busbar or sectionalized single busbar with discon-necting circuit breakers to improve substation availability.

Sectionalized single busbarSectionalized single busbar (also known as

H-configuration) is normally used in distributionsubstations. Parallel objects connected to the substationshould be split between the two bus sections; thisensures that the availability on for example, the mediumvoltage side of parallel transformers is very high.

ConventionalWith the conventional sectionalized single-busbar configura-tion, busbar disconnectors enable circuit breaker mainte-nance without deenergizing the busbar. Today the busbaradjacent disconnector requires more maintenance than thecircuit breaker, hence busbar section availability is decreasedcompared to a disconnecting circuit breaker solution.

Disconnecting Circuit Breaker With the disconnecting circuit breaker solution, all disconnec-tors are removed; hence the maintenance interval for thesubstation is increased from approximately every five years toevery fifteen years. Simplified interlocking confugurations

together with a smaller substation footprint and reducedmaintenance requirements will provide cost benefits comparedto the conventional solution. A sectionalized single bus withdisconnecting circuit breakers provides better performancethan a conventional double-busbar substation ( in normal ser-vice they are connected in the same way), which has alsobeen illustrated in the Availability and reliability section ofthe Application Guide.



Substation designDouble-busbar configurations

Double-busbar single breakerIn the double-busbar single-breaker conguration, theobjects are typically split between the busbars, so that thesubstation is connected as a sectionalized single busbarunder normal service conditions. When maintenance isrequired on one of the busbars or adjacent disconnectors,the other connected objects can be transferred to onebusbar. In this case, only the object where maintenanceis required is affected. A double busbar conguration alsoprovides a certain exibility in dedicating certain objects toa specic busbar in the substation.

Conventional The double-busbar, single-breaker configuration was intro-duced to enable maintenance of busbar adjacent discon-nectors without affecting the other connected objects in thesubstation. Maintenance of any of the equipment in the baywill take the connected object out of service.

Disconnecting Circuit Breaker The disconnecting circuit breaker is not applicable in adouble-busbar single-breaker solution because that configu-ration is based on disconnectors for switching between thebusbars. If the double-busbar single-breaker solution is under

consideration, it is recommended to use either a sectional-ized single busbar with disconnecting circuit breaker (as theyare connected in the same way, except when conventionaldisconnector maintenance is performed). If the substationreliability and availability is critical, a breaker-and-a-half ordouble-breaker configuration with disconnecting circuit break-ers should be considered.

Double-busbar single breaker withtransfer busbarThe double busbar with a transfer busbar works like adouble-busbar solution and has the same advantages.In addition to the double-busbar configuration,the added transfer busbar (green) will also enablemaintenance of the circuit breaker and its busbardisconnectors without affecting the connected object.Nonetheless, maintenance to the object adjacent andtransfer disconnector will take the object out of service.In service, the double busbar with a transfer busbar willbe connected as a sectionalized single busbar.

Conventional This solution is commonly used in transmission substationsand substations where high availability is a requirement.Operational procedures and maintenance requirements due tothe increased amount of disconnectors are both complicatedand time consuming.

Disconnecting Circuit Breaker The disconnecting circuit breaker is not applicable in adouble-busbar solution with a transfer busbar as that configu-ration is based on disconnectors for switching between thebusbars. If the double-busbar solution with a t ransfer busbar

is under consideration, ABB recommends the following pos-sible solutions.

Sectionalized single busbar with DCB (as they are connect-ed in the same way, except when disconnector or circuitbreaker maintenance is performed)

If the substation has especially high availability and reli-ability requirements, a double-breaker or breaker-and-a-half sollution with disconnecting circuit breakers is recom-mended.


33/60



Substation designDouble-breaker configurations

Double-breakerIn the double-breaker configuration, each object isconnected through a separate breaker to each of the twobusbars. Under normal service conditions, both breakersare closed. A single failure in a configuration like thiscan only affect one object. Extending a double-breakerconfiguration is considered easier than for a ring-busbaror breaker-and-a-half configuration, as the objects can beconnected from either side of the busbars.

ConventionalMaintenance of circuit breakers in this configuration does notaffect the incoming object. However, maintenance on the object adjacent disconnectors, which takes place approximatelyevery three to six years, will require that the object be takenout of service.

Disconnecting Circuit Breaker When disconnectors are removed, the disconnecting circuitbreaker switchyard requires only about 60% of the space ofthe conventional switchyard. Outages for connecting objectsare decreased as the maintenance interval of the disconnect-

ing circuit breakers is 15 years, instead of every three to sixyears as for conventional disconnectors.



Utility personnel can concentrate on a few larger projectsbecause the refurbished substations will not require servicefor many years after refurbishment.

Equipment-by-equipment-approach (not recommended)What is considered an advantage in a full substation refurbish-ment approach is the opposite in an equipment-by-equipmentapproach. In this approach, new technology can often notbe implemented in the substat ion and the engine (substationconfiguration setup) will stay the same. The main advantagewith an equipment-by-equipment refurbishment approach isa lower initial cost as equipment often is bought under frame

agreements, etc. With regard to the long term, this approachto refurbishing substations can be questioned.

In the case of equipment by equipment replacement, the dis-connecting circuit breaker can be a very suitable alternative toconventional disconnectors and circuit breakers.

Examples of substation refurbishmentIn the following example, a double busbar with a transferbusbar was upgraded to a sectionalized single busbar withdisconnecting circuit breakers. The old transfer busbar wasused to construct the new sectionalized single busbar with

disconnecting circuit breakers. This conversion resulted in a70% space reduction and increased reliability and availabilityfor the substation.

Refurbishment and extension

Substation refurbishment and extensionWhen refurbishing substations there are mainly two alternatives:

Full refurbishment (bay by bay/full substation refurbishment) Refurbishment equipment-by-equipment

The disconnecting circuit breaker can provide several ben-efits in substation extension and refurbishment, both full andequipment-by-equipment.

Full substation refurbishment approach (recommended) Although a full substation refurbishment costs more initially

compared to equipment-by-equipment refurbishment, it alsoprovides certain technological advantages. When the entire sub-station is refurbished at the same time, new upgraded technol-ogy with better reliability can be implemented in the substation.By performing a complete refurbishment, a number of technicaland commercial advantages can be obtained, such as:

Future work will be minimized since all equipment hassimilar vintage.

Single-line configuration can be adapted to developmentsin high-voltage apparatus and to any changes to theimportance of the substation in the network since it was

originally built. Outage times can be kept to a minimum by using theexisting equipment to keep the substation in service duringrefurbishment.



132 kV A

132 kV B

132 kV C

VT x 3

VT

ES x 3

CT

DS x 3

DS

ES

CT

VT

CB

DS x 3

DS

ES

CT

CT

SA

CB

TR

DS x 3

DS

DS

DS x 2

DS x 3

DS

ES

ES

CT

SA

CB

CB

VT

CT

DS

DS x 3

ES

CB

VT

CT

DS

DS x 3

ES

CB

CB

TR

132 kV

VT

VT VT VT

ES

ES ES ES

ES

VT

CT CT CT

SA

TR

DCB DCB DCB

VT VT VT

ES ES ES

CT CT CT

SA

TR

DCBDCB

DCB DCB

Before refurbishment of substation

After refurbishment of substa tion

Substation designRefurbishment and extension



Refurbishment and extension

The following section presents single-line diagramsthat show how a substation extension or equipmentreplacement can be configured.

Double busbar extension exampleIn the case extension of an existing double busbar eithera sectionalized single busbar or double breaker solution withdisconnecting circuit breakers would be suitable options, seethe single-line diagram information earlier in this chapter formore information.

Extension of traditional double busbar system

Example of extension of transfer busbar As discussed earlier in this chapter, even a transfer busbarsystem can be easily extended or replaced by a single or sec-tionalized single busbar with a disconnecting circuit breakers. The simplified solution with disconnecting circuit breakers willenhance the reliability and availability of the substa tion, whichcan be verified with availability calculations.

Extension of transfer bus system


38/60



Single busbar 420 kV

48 m

23 25

Single-busbar configurations for the higher voltages areprimarily recommended for use in tap-on substations. An example could be an added generation source to thetransmission grid.

Technical dataSystem voltage 420 kV Substation system Single busbarEquipment 2 lines and 2 transformers



An H-configuration or sectionalized single bus is mainly usedfor smaller distribution substations. With two or more incominglines and transformers, the availability of the medium voltagebusbar is very high.For distribution substations, a sectionalized single bus with dis-connecting circuit breakers provides better performance than aconventional double busbar substation, which has also beenillustrated in the availability section of the application guide.

Technical dataSystem voltage 145 kV Substation system Sectionalized single busbar

Equipment 2 lines and 2 transformers

Layout examplesSectionalized single busbar 145 kV

16 m

6 6 4



Sectionalized single busbar 420 kV

The DCB sectionalized single-busbar solution is often wellsuited for higher voltages, but this is dependent on the redun-dancy requirements of the substation. The DCB sectionalizedsingle-busbar configuration is very good for transmission gridswhen there are space and financial constraints.

Technical dataSystem voltage 420 kV Substation system Sectionalized single busbarEquipment 2 lines and 2 transformers

48 m

23 25



Layout examplesBreaker-and-a-half 145 kV

35 m

17.5 17.5

A breaker-and-a-half configuration is often used for largertransmission and primary distribution substations. In sub-stations with less than three diameters, it is recommended toalternate the transformer connections between the differentends of the diameters to increase substation reliability. Availability and reliability are high as each object is normallyfed from two directions.

Technical dataSystem voltage 145 kV Substation system Breaker-and-a-half Equipment 4 lines and 2 transformers



Breaker-and-a-half 420 kV

A breaker-and-a-half configuration is often used for largertransmission and primary distribution substations. In sub-stations with less than three diameters, it is recommended toalternate the transformer connections between the differentends of the diameters to increase substation reliability. Availability and reliability are high as each object is normallyfed from two directions.

Technical dataSystem voltage 420 kV Substation system Breaker-and-a-half Equipment 4 lines and 2 transformers

78 m

39 39



Layout examplesDouble breaker 145 kV

24 m

12 12

Double-breaker configurations provide the best performanceregarding availability, reliability and service conditions. As allobjects stay connected to both busbars at the same timethrough circuit breakers, there is no need for a bus coupler.If a failure occurs on a line or busbar, a maximum of oneobject will be affected.

Technical dataSystem voltage 145 kV Substation system Double breakerEquipment 4 lines and 2 transformers



Double breaker 420 kV

Double-breaker congurations provide the best performanceregarding availability, reliability and service conditions. The dou-ble-breaker solution is thus very popular in transmission gridswith high requirements on the above mentioned para-meters. The double breaker conguration is also very easy to extend.


58 m

29 29



Layout examplesRing bus 145 kV

22 m

11 11

Ring bus is suitable for smaller substations with up to six objects. Availability performance is very good as each object canbe fed from two directions. The disadvantage contra sectional-ized single bus is that the substation setup is more complicatedto extend, which also affects the overview of the substation.

Technical dataSystem voltage 145 kV Substation system Ring busEquipment 4 lines and 2 transformers



Ring bus 420 kV

Ring bus is suitable for smaller substations with up to six objects. Availability performance is very good as each object canbe fed from two directions. The disadvantage contra sectional-ized single bus is that the substation setup is more complicatedto extend, which also affects the overview of the substation.


48 m

24 24



Layout examplesCombination 145 kV

The combination se tup provides the best of two worlds, withan economical setup combined with a high performancesetup. Depending on the system requirements, the trans-formers can be connected with a double-breaker setup whilethe lines connect alternating to the two busbars.

Technical dataSystem voltage 145 kV Substation system CombinationEquipment 4 lines and 2 transformers

Transformer bay with double breakers

Line bay with a single breaker

24 m

12 12

24 m

12 12



Double breaker 145 kV, extra compact configuration

12 m

6 6

Double-breaker congurations provide the best performanceregarding availability, reliability and service conditions. As allobjects stay connected to both busbars at the same timethrough circuit breakers, there is no need for a bus coupler. If afailure occurs on a line or busbar, a maximum of one object willbe affected. The disconnecting circuit breaker can be placeddirectly under the busbar to create an extra compact solution.




18 m

DCB DCB

VT

VT VT

CT CT

PI + ES

Layout examplesIndoor substation ring bus 145 kV

The disconnecting circuit breaker enables high voltage, indoor AIS substations to be built. With an indoor ring bus congura-tion, availability and reliability are maximized while the cost of thesubstation is signicantly lower compared to a GIS substation.




Single-busbar indoor substations have very high reliabilityas they are in a protected environment. The required spaceis optimized so that the substat ion footprint can be directlycompared to a GIS substation, but at a lower cost.

Technical dataSystem voltage 145 kV Substation system Single busEquipment 2 lines and 2 transformers

19.2 m

6.6 m

DCB DCB DCB DCB VT VT

CT CT

SA PI

SA

Indoor substation single bus 145 kV



Maintenance operation procedureDouble breaker example

NOTE: The following examples should be seen as a simplied explanation describing the process of remov-ing a disconnecting circuit breaker from service while minimizing the outage consequence. The example maynot be seen as an instruction for how this work is to be performed. National and local safety directives mustbe followed by trained personnel in all work in substations. ABB accepts no responsibility whatsoever for anydamage to property or injury to personnel.

Scope of worksIsolate disconnecting circuit breaker for maintenance in order to be able to re-energize the line and busbar to minimize the outage time.

Part 1: Isolate disconnecting circuit breaker for maintenance by removal of conductors1. SC opens relevant disconnecting circuit breakers2. SC locks relevant disconnecting circuit breakers3. SC closes relevant earthing switches4. Maintenance personnel (SS - A) and (SS - B) enter the substation to apply padlocks on relevant disconnecting circuit breakers and

earthing switches.5. Maintenance personnel (SS - A) and (SS - B) performs zero voltage check and can set up maintenance earthing (portable earthing)6. Maintenance personnel (SS - A) can open clamps to remove/loosen conductors

The disconnecting circuit breaker is now isola ted with sec tion clearance for maintenance, while the line and busbar can be re turned toservice to minimize the outage time.

Part 2: Re-energize line and busbar to minimize outage time

7. Maintenance personnel (SS - A) and (SS - B) enter the substation to remove padlocks on relevant disconnecting circuit breakers andearthing switches.

8. SC opens relevant earthing switches9. SC unlocks relevant disconnecting circuit breakers

10. SC closes relevant disconnecting circuit breakers The line and second busbar is now back in service to minimize outage t ime.

Substationcontrol room A

(SS - A)

Switching center(SC)

Substationcontrol room B

(SS - B)

3 4

1 2 47 9 10

1 2 47 9 10

1 2 47 9 10

7 8

3 4

7 8

3 4

7 8

16 2 4

55

6

DCB in needof maintenance

1 2 47 9 10

5

Operation sequence in Single Line Diagram (SLD)



Scope of worksIsolate disconnecting circuit breaker for maintenance to be able to re-energize the busbar to minimize busbar outage.

Part 1: Isolate disconnecting circuit breaker for maintenance by removal of conductors1. SC opens relevant disconnecting circuit breakers2. SC locks relevant disconnecting circuit breakers3. SC closes relevant earthing switches4. Maintenance personnel (SS - A) and (SS - B) enter the substation to apply padlocks on relevant disconnecting circuit breakers and

earthing switches.5. Maintenance personnel (SS - A) and (SS - B) performs zero voltage check and can set up maintenance earthing (portable earthing)6. Maintenance personnel (SS - A) can open clamps to remove/loosen conductors

The disconnecting circuit breaker is now isolated with section clea rance for maintenance, while the busbar c an be returned to service tominimize outage time.

Part 2: Re-energize busbar to minimize outage time

7. Maintenance personnel (SS - A) enter the substation to remove padlocks on relevant disconnecting circuit breakers and earthing switches.8. SC opens relevant earthing switches9. SC unlocks relevant disconnecting circuit breakers10. SC closes relevant disconnecting circuit breakers

The busbar i s now back in service to minimize outage t ime.

Operation sequence in Single Line Diagram (SLD)

Substationcontrol room A

(SS - A)

Switching center(SC)

Substationcontrol room B

(SS - B)

3 4

1 2 47 9 10

1 2 47 9 10

1 2 4

5

7 8

3 4

3 4

6

DCB in needof maintenance

1 2 4

5

Sectionalized single busbar example



Functional specificationCreating a functional specification

A complete switchgear specification includes amongother things, specification of the primary electricapparatus and systems.Optimization of overall costs is a necessary measurein the deregulated energy market. The optimizationof substations and their development is an objectivecontinuously pursued by ABB. The focus is on functionalrequirements, reliability and cost over the total life cycle.

Specification The single line diagram (SLD) is the basis for the specification,which can be a complete apparatus specification or a func-

tional specification. An apparatus specification has the advantage that theengineer specifies exactly what he/she wants, and will receiveequivalent quotes from all bidders.

A functional spec ification enables the bidder to proposealternative ideas regarding apparatus and systems, and thebidder can sometimes quote more cost-effective solutionswith better performance.

In any event, it is important that the inquiry allows the bidderto quote alternatives to that specified in the specification,

without being disqualified.

Apparatus specification The conventional way is to specify in detail all the equipmentand the substation configuration/layout. All apparatus arespecified with quantity and data. The layout, which often isbased on a traditional approach, is also established. In thiscase, the asset owner receives equipment that is exactly whatis wanted and what the asset owner is accustomed to buying. This way of specifying the equipment normally permits noalternatives to propose other solutions with better performanceto lower the Life Cycle Cost.

To open the way for other solutions, a clause is sometimesincluded in the inquiry, stating that bidders are free to proposeother equipment, for example in accordance to IEC 62271-108.

Functional specification The main task for a substation is to transfer power in a con-trolled manner and to make it possible to make necessaryswitching/connections in the grid. Another way of specifyingthe equipment when planning a new plant or refurbishing anold substation can thus be to prepare a functional specication.

In this case, the bidder is free to propose the best solution,

taking in account all the benefits that can be gained by usingthe best technology and the latest developed apparatus andsystems, in combination with the requirements set for thesubstation and the network.

For example, basic requirements in a functionalspecification can be:

Number and type of system connections System electrical data Energy and transfer path through the system Unavailability related costs

Based on a functional specification, ABB can often proposean alternative solution, which provides better performance atconsiderably lower cost.

To back up decision-making, ABB can provide availabilitycalculations, life cycle cost ca lculations, environmental impactreports, etc.

As the supplier takes a greater part of design responsibility, itis important that all related questions such as scope of supply,demands from authorities, special design conditions etc. are

known at the beginning of the project.



Example of apparatus specification

Inquiry:Please submit a quote for apparatus for 132 kV switchgear infive bays according to the specification and enclosed single-line diagram:

5 High voltage circuit breaker 145 kV, 3150 A, 31.5 kA 12 Motor operated disconnector 145 kV, 2000 A, 31.5 kA with

integrated moto

Documents

1HSM 9543 23-03en DCB Application Guide Ed3 - 2013-09 - English