tp_109

The National Grid Company plc

Transmission ProcedureTP109

Numbering & Nomenclature of HV Apparatus

Issue 1April 1999

Authorised by

.....................................................

General Manager(on behalf of NGC Transmission)

8888 The National Grid Company plc 1999

No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by anymeans electronic, mechanical, photocopying, recording orotherwise, without the written permission of the NGCobtained from the issuing location.

The contents of The National Grid Company plcengineering documents are based on the needs of NGCand the conditions under which it operates. It should nottherefore be assumed that the specifications andrequirements stated therein necessarily meet the particularcircumstances and requirements of other organisations. No responsibility can therefore be accepted for any loss ordamage sustained as a result of using or relying on thedocuments.

Registered OfficeNational Grid HouseKirby Corner RoadCoventry CV4 8JY

Registered inEngland and WalesNo. 2366977

Published by:

The National Grid Company plcKelvin AvenueLeatherheadSurrey KT22 7ST

Administrative enquiries regarding this document should be directed to:

ET Administration Team at Leatherhead, Telephone: 01372 383818

This Document has been prepared by the following people:

Steve Pape (Author) System ManagementAlan Gregory Project ManagementLyndon Kilvington Network Services

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CONTENTS

1 PURPOSE..................................................................................................................................1

2 DEFINITIONS.............................................................................................................................1

3 RESPONSIBILITIES ..................................................................................................................1

4 PROCEDURE ............................................................................................................................2

5 REFERENCES...........................................................................................................................3

6 RECORDS..................................................................................................................................3

APPENDIX A..........................................................................................................................................4

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NUMBERING AND NOMENCLATURE

1 PURPOSE

1.1 This procedure describes the allocation of Numbering and Nomenclature to High Voltage Equipment onThe National Grid Company plc=s (NGC) Transmission System.

1.2 It implements Grid Code requirement Operating Code(OC) No. 11 "Numbering and Nomenclature of HighVoltage Equipment at Certain Sites." In that :

(a) NGC HV Equipment on Users' Sites; and

(b) User HV Equipment on NGC Sites;

shall have numbering and nomenclature in accordance with the system used by NGC.

1.3 To ensure, so far as possible, the safe and effective operation of the total Transmission System and toreduce the risk of human error faults by requiring, in certain circumstances, that the numbering andnomenclature of Users' HV Equipment shall be in accordance with the numbering system used by NGC.

1.4 The NGC system for numbering and nomenclature is derived from the ex-CEGB Document - OperationMemorandum No. 5. This Transmission Procedure has been updated to reflect the introduction of newtypes of equipment.

2 DEFINITIONS

2.1 OC11 applies to NGC and to Users, which OC11 defines as: Generators, Suppliers, Non-EmbeddedCustomers and any other person with a User System directly connected to the NGC Transmission Systemto which Power Stations and/or Customers are connected.

2.2 User Site

A site owned (or occupied pursuant to a lease, licence or other agreement) by a User in which there is aConnection Point. For the avoidance of doubt, where a site is owned by NGC but occupied by a User, theSite is a User Site.

2.3 NGC Site

A site owned (or occupied pursuant to a lease, licence or other agreement) by NGC in which there is a Connection Point. For the avoidance of doubt, where a Site is owned by a User but occupied by NGC,the site is an NGC Site.

3 RESPONSIBILITIES

3.1 System Management are responsible for agreeing with other NGC Business Units the application of theprinciples of this procedure.

3.2 The NGC Business Unit which initiates the modification to the NGC HV system will be responsible forbeginning the process of agreeing the numbering and nomenclature. The timing of this process shouldbe sufficient to allow discussion and approval prior to excessive costs being incurred.

3.3 The NGC Business Unit which initiates modifications to overhead lines will be responsible for approachingEngineering and Technology who will allocate line route letters and circuit identification plates (CIP). Ifnecessary the allocated line route letters and CIP will be agreed with Network Services.

4 PROCEDURE

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4.1 The terms 'Disconnector' and 'Isolator' are synonymous but this document uses the preferred term'Disconnector' throughout. The choice of which term to use at any particular location shall be made asfollows:-

4.2 Existing and minor extensions to existing substations shall retain the predominant existing term. However,where any future extension forms a major part of the installation the term 'Disconnector' shall be used forall new equipment and the existing equipment nomenclature shall be changed to 'Disconnector'. All futuresubstations should use the term 'Disconnector' throughout.

4.3 An overhead line route and its towers shall not be numbered or colour coded such that they could bereadily confused with any other geographically close route or tower. The designation letters Q, I, J and Owould not be considered appropriate for use in these circumstances.

4.4 NGC HV Equipment on Users' Sites (OC11.4.2)

(a) NGC HV Equipment on Users' Sites will have numbering and nomenclature in accordance with the systemused by NGC.

(b) When NGC is to install its HV Equipment on a User's Site, NGC shall notify the relevant User of thenumbering and nomenclature to be adopted for that HV Equipment at least eight months prior to proposedinstallation.

(c) The notification will be made in writing to the relevant User and will consist of both a proposed OperationDiagram incorporating the proposed new NGC HV Equipment to be installed, its proposed numbering andnomenclature, and the date of its proposed installation.

(d) The relevant User will respond in writing to NGC within one month of the receipt of the notification,confirming receipt and confirming either that any other HV Equipment of the relevant User on such Sitedoes not have numbering and/or nomenclature which could be confused with that proposed by NGC, or,to the extent that it does, that relevant other numbering and/or nomenclature will be changed beforeinstallation of the NGC HV Equipment.

(e) The relevant User will not install, or permit the installation of, any HV Equipment on such Site which hasnumbering and/or nomenclature which could be confused with NGC HV Equipment which is either alreadyon that Site or which NGC has notified that User will be installed on that Site.

4.5 User HV Equipment on NGC Sites (OC11.4.3)

(a) User HV Equipment on NGC Sites shall have numbering and nomenclature on the basis of that used byNGC.

(b) When a User installs new HV equipment or replaces existing HV equipment on an NGC site and wishesto adopt new numbering and nomenclature the User shall notify NGC in writing of equipment details,numbering and nomenclature at least eight months prior to installation. This notification should be inOperation Diagram format and include the proposed date of utilisation.

(c) NGC will respond in writing within one month on the acceptability of the proposed numbering andnomenclature. If it is not acceptable NGC will indicate suitable alternatives which the user shall adopt.

4.6 Changes (OC11.4.4)

Where NGC in its reasonable opinion has decided that it needs to change the existing numbering ornomenclature of NGC HV Equipment on a User's Site or of User's HV Equipment on an NGC Site:

(a) the provisions of paragraph OC11.4.2 shall apply to such change of numbering or nomenclature of NGCHV Equipment with any necessary amendments to those provisions to reflect that only a change is beingmade and;

(b) in the case of a change in the numbering or nomenclature of User's HV Equipment on an NGC Site, NGCwill notify the User of the numbering and/or nomenclature for that HV Equipment. This notification is to

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be in a form similar to that envisaged under OC11.4.2 and at least eight months prior to the change beingneeded. The User will respond in writing to NGC within one month of the receipt of the notification,confirming receipt.

In either case the notification shall indicate the reason for the proposed change.

4.7 Availability of current system (OC11.4.5)

User's will be provided upon request with details of NGC's current numbering and nomenclature systemin order to assist them in planning the numbering and nomenclature for their HV Equipment on NGC Sites.

4.8 Labelling (OC11.4.6)

When either NGC or a User installs HV Equipment which is the subject of OC11 either NGC or the User,as the case may be, shall be responsible for the provision and erection of clear and unambiguous labellingshowing the numbering and nomenclature. Where either NGC or a User is required by OC11 to changethe numbering and/or nomenclature of HV equipment, NGC or the User, as the case may be will beresponsible for the erection of clear and unambiguous labelling showing the new numbering andnomenclature by the required date.

4.9 Changes to numbering system (OC11.4.7)

NGC will not change its system of numbering and nomenclature embodied in this document, other thanto reflect new or newly adopted HV Equipment technology.

4.10 It is not intended that any of the requirements of this document be applied retrospectively, except wherethe safety implications can justify the necessary expenditure.

5 REFERENCES

5.1 Operating Code (OC) 11 ANumbering and Nomenclature of High Voltage Equipment at CertainSites@

5.2 TP 119 Transmission Operation Diagrams & Technical Data

6 RECORDS

6.1 Not applicable


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APPENDIX A

Numbering and Nomenclature of HV Equipment

(Update of CEGB Document Operation Memorandum No. 5Numbering and Nomenclature of HV Apparatus on the CEGB Grid Systemissue 3, 6 June 1983)

PHILOSOPHY

To ensure, so far as possible, the safe and effective operation of the total Transmission System and to reduce therisk of human error faults by requiring, in certain circumstances, that the numbering and nomenclature of HVEquipment shall be in accordance with a standard numbering system.

A1 NAMING OF STATIONSA2 SEQUENCE NUMBERING OF EQUIPMENT IN SUBSTATIONSA3 IDENTIFICATION OF CIRCUITSA4 IDENTIFICATION OF BUSBARSA5 IDENTIFICATION OF TRANSFORMERSA6 IDENTIFICATION OF REACTORS, COMPENSATORS AND BOOSTERSA7 IDENTIFICATION OF FREE STANDING VOLTAGE AND CURRENT TRANSFORMERSA8 LABELLINGA9 400 kV SWITCHGEARA10 275 kV SWITCHGEARA11 132 kV SWITCHGEARA12 SWITCHGEAR BELOW 132 kV (EXCLUDING METAL ENCLOSED)A13 METAL ENCLOSED TYPE SWITCHGEAR BELOW 132 kVA14 HV DC SWITCHGEARA15 NOMENCLATURE FOR SHORTING/DISCHARGE SWITCHES ASSOCIATED WITH STATIC

CAPACITORS. COMPENSATORS AND FILTERSA16 EARTHING SWITCHGEARA17 NEUTRAL EARTHING EQUIPMENTA18 GAS ZONE NUMBERINGA19 SPECIAL LAYOUTSA20 ABBREVIATIONS

DIAGRAMS 1-11 - EXAMPLE NUMBERING AND NOMENCLATURE DIAGRAMS FOR DIFFERINGCONFIGURATIONS

A1 NAMING OF STATIONS

A1.1 Substations (Switching Stations or Transforming Stations)

A1.1.1 Substation names shall be nominated by Commercial and System Strategy, who will, where necessary,consult and agree the name to be adopted with the SM, Operational Services. ET NetworkReplacement will maintain a database of substation names and short codes for NGC and other Users.

A1.1.2 No substation shall be given the same name as that of any other NGC substation or User Site on thesystem unless it is located on the same site as an existing NGC substation or user site, or as allowedfor in paragraph A1.1.4.

A1.1.3 No substation shall be given a name that could be readily confused with the name of any othersubstation or user site on the system.


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A1.1.4 Where two or more substations are located geographically close together they may be namedindependently or alternatively given the same name followed by their respective voltages or by letters:-

eg Cardiff EastCardiff West

West Weybridge 275 kVWest Weybridge 132 kV

A1.2 User Sites

A1.2.1 User site names shall be nominated by such user, who will consult on and agree the name to be adoptedwith NGC Commercial and System Strategy.

A1.2.2 Except in special circumstances, no user site shall be given the same name, or one that could readilybe confused with, that of any other user site or substation on the system unless it is located on the samesite as an existing user site.

A1.2.3 Where circumstances dictate that a user site needs to assume the name of an existing substation oruser site or a name that could readily be confused with an existing substation or user site, NGCCommercial and System Strategy will consult and agree the necessary adjustment of names with therelevant Users.

A1.2.4 Where two or more user sites are located geographically close together they may be namedindependently or alternatively given the same name followed by a letter:-

eg Dungeness 'A'Dungeness 'B'

A2 SEQUENCE NUMBERING OF EQUIPMENT IN SUBSTATIONS

A2.1 Further to the requirements of section A5.6 for all transformers to be uniquely numbered and section6 for reactors, compensators and boosters to be uniquely numbered, the following will apply:

A2.1.1 Where the above installations are associated with an even numbered busbar section, then an evennumbered sequence shall be used and vise versa.

A2.1.2 Where the above installation is connected to the system via a static compensator transformer, then thecircuit numbering will follow the sequence that is used for other transformer circuits.

A2.1.3 Where the next number in sequence could lead to confusion or ambiguity with adjacent equipment, thefollowing number in sequence should be used.

A2.2 Sequence numbering which could lead to ambiguity at substations of different voltage on the same siteshould be avoided.

A3 IDENTIFICATION OF CIRCUITS

A3.1 The identification of circuits connecting substations at different named sites shall be as follows:-

A3.1.1 A circuit connecting two substations shall be designated by the names of the substations concerned inalphabetical order of sites.

eg Cottam - Grendon

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A3.1.2 A circuit connecting three or more substations shall be designated by the names of all the substationsconcerned in alphabetical order of sites, tee points excepted.

eg Aberthaw-Upper Boat-CilfynyddHalewood-BOC Woodend-Widnes-Rainhill

A3.1.3 Parallel circuits between the same substations shall be designated in accordance with paragraphsA3.1.1 or A3.1.2 above and shall be numbered uniquely.

eg Grendon-Sundon 1Grendon-Sundon 2

East Claydon-Amersham Main-Iver 1East Claydon-Amersham Main-Iver 2

A3.2 The identification of circuits connecting, at the same voltage, substations at the same named site shallbe as follows:-

A3.2.1 A circuit connecting two substations shall be designated by the names of the two substations concernedand called an Interconnector.

A3.2.2 Parallel circuits between the same substations shall be identified in accordance with paragraph A3.2.1above and shall be numbered uniquely.

A4 IDENTIFICATION OF BUSBARS

A4.1 The numbering and nomenclature of busbars other than those associated with power station auxiliariesshall be as follows:-

A4.1.1 Nominal busbar voltage (400 kV, 275 kV, 132 kV, etc).

A4.1.2 Busbar designation (Main Busbar, Reserve Busbar, Mesh Corner, etc).

A4.1.3 Busbar section number (1, 2, 3, etc).

eg 275 kV Main Busbar 1

A4.1.4 Sections of busbars of the same nominal voltage and busbar designation shall be numberedconsecutively from one end of the substation to the other. Main and reserve busbars shall havecorresponding numbering.

A4.1.5 In the case of substations where one section of one busbar is common to two sections of an associatedbusbar, the former shall bear the numbers of both corresponding sections of the latter.

eg 400 kV Main Busbar 1400 kV Main Busbar 2400 kV Reserve Busbar 2

A4.1.6 The busbar section number shall be omitted in those cases where the busbar is a single busbar havingno sectioning facilities.

eg 275 kV Main Busbar

A4.1.7 In the case of a mesh type substation the corners of the mesh shall be numbered consecutively in ananti-clockwise direction when viewed from above.


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A4.2 The numbering and nomenclature of the principal busbars associated with power station auxiliaries shallbe as follows:-

A4.2.1 Nominal busbar voltage (11 kV, 6.6 kV, 3.3 kV etc).

A4.2.2 Busbar designation (Station Board, Unit Board).

A4.2.3 Busbar number (1, 2, 3, etc). This number shall be the number of the associated transformer orgenerator.

eg 11 kV Unit Board 1

A4.2.4 In the case of busbars with sectioning facilities the word ASECTION@ followed by a consecutive numberor letter shall be added.

eg 11 kV Unit Board 1 Section 1

A5 IDENTIFICATION OF TRANSFORMERS

A5.1 The identification of all transformers (except earthing transformers) shall include a prefix indicating theratio of the nominal voltages eg 400/132 kV.

A5.2 The numbering and nomenclature of transformers connected to the NGC System, other than thosedirectly associated with converting, compensating equipment or generators and their auxiliaries and withdue regard to the development of the substation, shall be as follows:-

A5.2.1 A transformer with a nominal primary voltage of 400 kV or 275 kV which connects with a lower voltagesystem, shall be designated a SUPERGRID TRANSFORMER. All such Supergrid Transformers shallbe numbered uniquely in relation to each other and to any other transformers, excluding generatortransformers, with 400 kV or 275 kV windings at a particular named site and where appropriate, theprovisions of paragraphs A5.3, A5.4 and A5.5 shall apply.

A5.2.2 A transformer with a nominal primary voltage of 132 kV which connects with a lower voltage system shallbe designated a GRID TRANSFORMER. All such transformers shall be numbered uniquely in relationto each other and to any other transformers, excluding generator transformers, with 132 kV high voltagewindings at a particular named site and where appropriate, the provisions of paragraphs A5.3, A5.4 andA5.5 shall apply. This nomenclature shall apply at named sites where 66 kV is the primary voltage andthere is no transformation from 132 kV.

A5.2.3 A transformer with the next highest primary voltage below that of a Grid Transformer shall be designateda INTERBUS TRANSFORMER and all such transformers at a particular named site shall be numbereduniquely.

A5.2.4 Other transformers at a particular named site shall be designated by reference to the ratio of the nominalvoltages and shall be numbered uniquely.

eg 11/6.6 kV Transformer 1

A5.3 A transformer connected to ac/dc converting equipment and provided for the transmission of power shallbe designated CONVERTER TRANSFORMER. All such transformers shall be numbered uniquely ata particular named site and where appropriate, the provisions of paragraphs A5.2.1 or A5.2.2 shallapply.

A5.4 A transformer provided at a user site to supply the station board and having a nominal high voltage of400 kV, 275 kV or 132 kV shall be designated STATION TRANSFORMER. All such transformers shallbe numbered uniquely at a particular named site and where appropriate, the provisions of paragraphsA5.2.1 or A5.2.2 shall apply.

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A5.5 A transformer provided solely for the purpose of connecting an item of compensating equipment, andnot for the transmission of power, shall be designated COMPENSATOR TRANSFORMER. All suchtransformers shall be numbered uniquely at a particular named site.

A5.6 All transformers covered by the provisions of paragraphs A5.2, A5.3, A5.4 and A5.5 and being of thesame nominal high voltage shall be numbered uniquely at a particular named site.

eg At a 400 kV site:-400/275 kV Supergrid Transformer 1400/11 kV Station Transformer 2400/275 kV Supergrid Transformer 3400/132 kV Converter Transformer 4400/132 kV Supergrid Transformer 5400/11 kV Station Transformer 6400/132 kV Supergrid Transformer 7

A5.7 The numbering and nomenclature of transformers directly associated with users equipment shall be asfollows:-

A5.7.1 A transformer connected to a generator and provided for the transmission of the generator output to themain system shall be designated GENERATOR TRANSFORMER and shall be numbered the sameas the associated generator.

A5.8 A transformer provided to supply a power station unit board and connected to a generator shall bedesignated UNIT TRANSFORMER and shall be numbered the same as the associated generator. Where more than one UNIT TRANSFORMER is provided the individual transformers shall be numberedas the associated generator and be identified by the addition of a consecutive letter as a suffix.

A5.9 Where two or more transformers in a substation or power station are banked on to a circuit breaker oneither the high voltage or the low voltage side the individual transformers shall have the same numberand be identified by the addition of a consecutive letter as a suffix.

eg 275/132 kV Supergrid Transformer 1A275/132 kV Supergrid Transformer 1B

A5.10 The numbering and nomenclature of a transformer directly connected to another transformer shall beas follows:-

A5.10.1 A transformer providing a system neutral connection and not supplying auxiliaries shall bear thedesignation and number of the transformer to which it is connected followed by the voltage of thewinding to which the transformer is connected and the words EARTHING TRANSFORMER.

eg Supergrid Transformer 3 13 kV Earthing Transformer.

A5.10.2 A transformer supplying local auxiliaries and not providing a system neutral connection shall bear thedesignation and number of the transformer to which it is connected, and the voltage ratio of the auxiliarytransformer, followed by the words AUXILIARY TRANSFORMER.

eg Supergrid Transformer 4 13 kV/415V Auxiliary Transformer.

A5.10.3 A transformer providing a system neutral connection and supplying auxiliaries shall bear the designationand number of the transformer to which it is connected, followed by the voltage of the winding to whichthe transformer is connected and the words EARTHING AND AUXILIARY TRANSFORMER, with thevoltage of the equipment supplied preceding the word AUXILIARY.

eg Supergrid Transformer 1 13 kV Earthing and 415V Auxiliary transformer.

A5.10.4 The overriding concern is that equipment should be identified within isolatable zones. (See diagram 10.)


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A6 IDENTIFICATION OF REACTORS, COMPENSATORS AND BOOSTERS

A6.1 At nuclear power station sites the term 'INDUCTOR' shall be used instead of 'REACTOR' to describean electrical reactor, in order to avoid any possible confusion with nuclear reactors.

A6.1.1 The preferred name for capacitive Compensation Circuits will be Mechanically Switched Capacitors.These may be made up of one or more individually switched static capacitors.

A6.2 The numbering and nomenclature of reactors/inductors, capacitors, compensators and boosters shallbe as follows:-

A6.2.1 Nominal Voltage eg 400 kV, 66 kV

A6.2.2 Description eg series reactor, static capacitor. In all cases the word reactor, capacitor or booster shallbe qualified by an appropriate adjective.

A6.2.3 Number

(a) In the case of equipment connected to a mesh type substation this number shall be the number of theassociated mesh corner.

(b) In the case of equipment connected to a transformer tertiary winding this number shall be the numberof the associated transformer except for equipment identified under section A6.1.3.3. If the associatedtransformer is a banked transformer the appropriate letter shall also be included.

(c) In the case of a relocatable SVC (RSVC) this will be a unique name letter (A,B...Z, AA, AB, ... asappropriate). A central register of RSVC identifications will be maintained to which reference should bemade when determining nomenclature for any new RSVC.

(d) Relocatable SVC elements situated within a supergrid transformer isolation zone shall have dual naming

eg Supergrid Transformer 1 / RSVC A 13 kV Earthing and 415V Auxiliary transformer.

(e) In other cases this number shall be a sequence number.

A6.2.4 Where two items qualify for the same number and nomenclature, the word WINDING shall be addedto reactor nomenclature followed by an identification letter. Similarly the work BANK shall be added tocapacitor nomenclature followed by an identification letter.

eg 13 kV Shunt Reactor 4B Winding A13 kV Static Capacitor 1 Bank A

A6.3 The information given above for shunt reactors is illustrated in Diagram 8.

A7 IDENTIFICATION OF FREE STANDING VOLTAGE AND CURRENT TRANSFORMERS

A7.1 The nomenclature of free standing voltage and current transformers shall be as follows.

A7.2 The designation and number of the associated equipment or circuit to which the voltage or currenttransformer is directly connected.

A7.3 The nominal voltage.

A7.4 The words VOLTAGE TRANSFORMER or CURRENT TRANSFORMER as appropriate.

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A7.5 Where two items qualify for the same nomenclature, reference to adjacent plant/equipment may beused.

eg Supergrid Transformer 2 400 kV Voltage Transformer.X120 400 kV Current Transformer (X124 side).

A8 LABELLING

A8.1 Switchgear Labelling

A8.1.1 All switchgear should carry the labelling identified in this procedure along with the circuit designation

eg for 400/132 kV SGT3 HV circuit breaker:

SGT3 X310

A8.1.2 Where the operation of equipment requires action at phase level, each phase shall be clearly identified.

A8.2 Panel Labelling

A8.2.1 Circuits

(a) Switchgear control, protection equipment and metering panels associated with a circuit shall be labelledin accordance with Section 3, except that the name of the substation at which the panel is located shallbe omitted. For multi-ended circuits the order of naming should be in order of proximity.

eg At Walpole on the Walpole-Norwich 1 and 2 circuits labels would read:Norwich 1,Norwich 2.

At Kingsnorth on the Kingsnorth-Tilbury-Rayleigh circuit, labels would read:Tilbury-Rayleigh

(b) Each control handle or other control facility shall have a label adjacent to it designating the equipmentcontrolled.

eg L45 (see sections 9-17).

(c) Where a circuit is terminated with a transformer circuit breaker, labelling shall be in accordance with theprovisions of paragraph A8.2.2.4.

A8.2.2 Transformer Circuits

(a) Switchgear control, protection equipment and metering panels associated with a transformer circuit shallbe labelled in accordance with Section 5. Where the use of the full identification is impractical thevoltage ratio prefix may be omitted.

eg Supergrid Transformer 6.

(b) Each control handle or other control facility shall have a label adjacent to it designating the equipmentcontrolled.

eg 180 (see sections 9-17).

(c) HV and LV relay panel labelling for a typical 400/132 kV Supergrid Transformer shall be:-

Supergrid Transformer 1 400 kV Relay PanelSupergrid Transformer 1 132 kV Relay Panel

(d) At substations where a transformer circuit breaker acts as the termination of a line circuit the HV and


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LV relay panels shall include the circuit designation in accordance with paragraph 14.1.1.

eg At Alverdiscott on the Indian Queens -Alverdiscott - Taunton 1 circuit, labels would read:

Supergrid Transformer 1 (Indian Queens - Taunton 1) 132 kV relay panel

A8.2.3 Other Equipment

(a) Switchgear control, protection equipment and metering panels associated with other equipment shallbe labelled in accordance with the nomenclature of the equipment.

eg 13 kV Shunt Reactor 4A13 kV Static Capacitor 3

(b) Separate labelling of protection relays, etc. shall be provided where appropriate.

eg Winding ABank B

(c) Each control handle or other control facility shall have a label adjacent to it designating the equipmentcontrolled.

eg 4KO (see sections 9-17)

A9 400 kV SWITCHGEAR

A9.1 The nomenclature of 400 kV switchgear shall be the designation and number of the associatedequipment, followed by a description of the function of the particular item of switchgear.

A9.2 The numbering of 400 kV switchgear shall be three or four numbers preceded by the letter 'X'.

A9.2.1 The first number (or two numbers in a sequence of four) shall be used to denote the sequence ofswitchgear groups in any one class in a substation.

(a) In the case of a generator circuit the first number shall be the generator number.

(b) In the case of a transformer circuit connecting busbars at the same named site, the first number shallbe the number of the transformer or transformer bank.

(c) The switchgear groups of line circuits shall be numbered from an end of the substation that is notdesigned to be extended. If a substation is designed to be extended in both directions the switchgeargroups on one side of the substation shall be given odd numbers and those on the other shall be giveneven numbers, commencing from a sectioning or other suitable point.

(d) A transformer circuit connecting busbars at different named sites shall be considered as a transformercircuit only at the substation where that transformer is located, with the exception that line numberingbe applied in the case of an earthing switch on the line side of the circuit disconnector. Otherterminations of the circuit shall be considered as line circuits.

(e) In the case of a bus-coupler; the number 1 bus-coupler circuit breaker shall connect main and reservebusbars in section 1, number 2 bus-coupler circuit breaker shall connect main and reserve busbars insection 2, etc.

(f) In the case of a bus-section; number 1 bus-section circuit breaker shall connect busbar sections 1 and2, number 2 bus-section circuit breaker shall connect busbar sections 2 and 3, etc.

(g) In the case of a mesh type substation, equipment numbering shall be determined by the corner numberto which it is connected (Bus Section 1 shall be between mesh corners 1 and 2, etc.).

(h) Where the same switchgear is used to control a line and a local transformer, then line numbering shall

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be applied to the switchgear.

A9.2.2 The second number shall be used to denote the class of switchgear group as given in table 1 below:-

TABLE 1

*0* - Line*1* - Transformer high voltage side*2* - Main Bus Section

Mesh BusbarInterconnector (within a substation)

*3* - Bus Coupler*4* - Quad Booster or Series Reactor*5* - Static Shunt Compensator*6* - Reserve Bus Section*7* - (Spare)*8* - Transformer low voltage side*9* - Generator

Synchronous Compensator

(a) Switchgear inserted in lines associated with teed circuits at a named site, other than the high voltageterminations of the circuits, shall be considered as main busbar section switchgear.

(b) Switchgear provided specifically for the purpose of switching a transformer from one circuit to anothershall be considered as main busbar section switchgear.

(c) The third number shall be used to denote the function of the particular item of switchgear in the groupas given in table 2 below:-

TABLE 2

**0 - Circuit breaker (excluding lines)Circuit breaker (2nd choice lines)Circuit breaker associated with main busbar on double switched equipmentSwitch disconnecter (lines)

**1 - Earthing switch**2 - By-pass disconnecter**3 - Circuit disconnecter**4 - Main busbar disconnecter**5 - Circuit breaker (lines)

Circuit breaker (2nd choice excluding lines)Circuit breaker associated with reserve busbar on double switched equipmentSwitch disconnecter (excluding lines)

**6 - Reserve busbar disconnecterMesh opening corner disconnecter

**7 - Circuit breaker disconnecter, busbar side**8 - Main busbar disconnecter (2nd choice)**9 - Reactor tie busbar disconnecter

Reserve busbar disconnecter (2nd choice)

A9.2.4 Where more than one item in a group qualifies for a particular number the number shall be suffixed byconsecutive letters, commencing from the circuit termination inwards to the busbar selectordisconnectors.

A9.2.5 In the case of banked circuits the numbers shall be suffixed by the identification letter of the appropriatecircuit for those items of equipment which are not common to all the circuits of the bank. In general,


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a suffix shall not be used for items common to all circuits of the bank except in those instances wherethe number is repeated, when an appropriate letter suffix shall be added.

A9.3 The implementation of both the 400 kV nomenclature and numbering is illustrated in table 5 at the endof this document and in diagrams 1-4.


A10.1 The nomenclature of 275 kV switchgear shall be the designation and number of the associatedequipment followed by a description of the particular item of switchgear.

A10.2 The numbering of 275 kV switchgear shall be made up as follows:-

A10.2.1 A letter shall precede two or three numbers and shall be used to denote the class of switchgear groupas given in the Table 3 below:-

TABLE 3

L** - LineH** - Transformer high voltage sideS** - Main Bus Section

Mesh BusbarInterconnector (within a substation)

W** - Bus CouplerR** - Quad Booster or Series ReactorK** - Static Shunt CompensatorP** - Reserve Bus SectionZ** - (Spare)T** - Transformer low voltage sideM** - Generator

Synchronous Compensator

A10.2.2 The first number (or two numbers in a sequence of three) shall be used to denote the sequence ofswitchgear groups in any one class on a named site. The number shall be derived in accordance withsection A9.2.1

A10.2.3 The second number shall be used to denote the function of the particular item of switchgear in the groupas given in Table 2. (Section A9.2.3).

A10.2.4 The provisions of paragraphs A9.2.2.1, A9.2.2.2, A9.2.4 and A9.2.5 shall apply.


A11.1 The nomenclature of 132 kV switchgear shall be the designation and number of the associatedequipment followed by the function of the particular item of switchgear.

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A11.2 The numbering of 132 kV switchgear shall be in accordance with section A9.2 (numbering of 400 kVswitchgear) excluding the prefix 'X', except for 11.3 below.

A11.3 In the case of banked circuits the numbers shall be suffixed by the identification letter of the appropriatecircuit for those items of equipment which are not common to all the circuits of the bank. If a numberof items qualify for the same number and letter sequence, a further number suffix shall be used as insection A16.1.2

A12 SWITCHGEAR BELOW 132 kV (EXCLUDING METAL ENCLOSED)

A12.1 The nomenclature of switchgear at nominal voltages lower than 132 kV shall be the designation andnumber of the associated equipment followed by a description of the function of the particular item ofswitchgear.

A12.2 The numbering of switchgear at nominal voltages lower than 132 kV, other than those associated withequipment connected to Supergrid or Grid Transformer tertiary windings, shall be made up as follows:-

A12.2.1 A letter prefixed and suffixed by a number.

A12.2.2 The number prefixing the letter shall be used to denote the sequence of switchgear groups in any oneclass in a substation.

(a) In the case of a generator circuit, the number shall be the generator number.

(b) In the case of a transformer circuit connecting busbars at the same named site, the number shall bethe number of the transformer or transformer bank.

(c) The numbering of the circuit breaker on the low voltage side of a Supergrid Transformer shall beSUPERGRID followed by the number and letter, if any, of the transformer.

eg Supergrid 1A

(d) The numbering of the circuit breaker on the low voltage side of a Grid Transformer shall be GRIDfollowed by the number and letter, if any, of the transformer.

eg GRID 1A

(e) In the case of the transformer having two or more low voltage circuit breakers, these shall be identifieduniquely in line with paragraph A13.1.4

(f) In all other cases the number given shall be derived in accordance with paragraphs A9.2.1.3, A9.2.1.4,A9.2.1.5, A9.2.1.6, A9.2.1.7 and A9.2.1.8.

A12.2.3 The letter shall be used to denote the class of switchgear group as given in Table 3 (Section A10.2.1.1)with the addition given below.

(a) A - Certain Auxiliary Equipment

eg - Grid Transformer 1 LV Voltage Transformer Disconnecter - 1A3

(b) In the case of earthing switchgear solely associated with a transformer tertiary winding, the letter usedshall indicate this connection, ie. the letter 'T' shall be used. (See diagram 8).

A12.2.4 The number suffixing the letter shall be used to denote the function of the switchgear in the groups asgiven in Table 2 (Section 9.2.3).


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A12.2.5 Where more than one item qualifies for a particular number the provision of paragraphs A9.2.4 andA9.2.5 shall apply.

A12.3 The numbering of switchgear associated with equipment connected to Supergrid tertiary windings shallbe made up as follows:-

A12.3.1 The number, and letter where appropriate, of the associated Supergrid Transformer. Except in the caseof a relocatable SVC, see section A6.1.3.3

A12.3.2 A letter to denote the class of switchgear group (Sections A10.2 and A12.2.3).

eg K for a static shunt compensatorM for a synchronous compensator

A12.3.3 A number to denote the function of the switchgear in the group as given in Table 2 (Section A9.2.3).

A12.3.4 Where more than one item in a group qualifies for a particular number, the number shall be suffixed byunique letters.

eg Shunt Reactor associated with 400/132 kVWinding A circuit breaker - 1KOAWinding B circuit breaker - 1KOB

Synchronous compensator associated with400/275 kV Supergrid Transformer 2B:-Main Circuit breaker- 2BMO1Starting Circuit breaker- 2BMO2Running Circuit breaker- 2BMO3

A12.3.5 The information given above for shunt reactors is illustrated in Diagram 8.

A12.4 A comprehensive summary of the nomenclature and numbering of "Switchgear below 132 kV" other thanLV Metal Enclosed is shown in tabular form in table 5 at the end of this document, whilst theimplementation is illustrated in Diagram 1.

A13 METAL ENCLOSED TYPE SWITCHGEAR BELOW 132 kV

A13.1 The numbering and nomenclature of metal enclosed type switchgear associated with transformers shallbe as follows:-

A13.1.1 Switchgear on the low voltage side of a Supergrid Transformer shall be named SUPERGRID followedby the number and letter, if any, of the transformer.

eg SUPERGRID 1A.

A13.1.2 Switchgear on the high voltage side of a grid Transformer shall be named GRID T followed by thenumber and letter, if any, of the transformer and the nominal voltage of the switchgear.

eg GRID T1A 66 kV

A13.1.3 Switchgear on the low voltage side of a Grid Transformer shall be named GRID followed by the numberand letter, if any, of the transformer.

eg GRID 1B

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A13.1.4 In the case of a transformer having two or more low voltage circuit breakers, these shall be identifiedas follows:-

(a) In the case of a transformer having a number only, by the addition of consecutive letters.

eg Switchgear associated with Grid transformer 1:-

GRID 1AGRID 1B

(b) In the case of a transformer having a number and letter, by the addition of consecutive numbers or othersuitable qualification.

eg Switchgear associated with Grid Transformer 1B:-

GRID 1B1 or GRID 1B NORTHGRID 1B1 or GRID 1B SOUTH

A13.1.5 Switchgear associated with an Interbus Transformer shall be named INTERBUS followed by the numberand letter, if any, of the transformer and the nominal voltage of the switchgear.

eg INTERBUS 1 33 kVINTERBUS 1 11 kV

A13.1.6 Switchgear associated with other Transformers excluding power station auxiliaries, shall be designated'T' followed by the number and letter, if any, of the transformer and the nominal voltage of theswitchgear.

eg T1 11 kVT1 6.6 kV

A13.1.7 Switchgear associated with a Station Transformer shall be named STATION TRANSFORMER followedby the number and letter, if any, of the transformer and prefixed by the voltage.

eg 11 kV Station Transformer 2A

A13.1.8 Switchgear associated with a Unit Transformer shall be named UNIT TRANSFORMER followed by thenumber and letter, if any, of the transformer and prefixed by the voltage.

eg 11 kV Unit Transformer 4

A13.2 Switchgear associated with feeder circuits, excluding power station auxiliaries, shall be named byreference to all the terminations of the circuit excepting the location of the switchgear, including in thecase of parallel circuits, the appropriate number.

eg At West Ham: Barking - East Ham 3

A13.3 The numbering and nomenclature of Busbar Section, Busbar Coupler, Busbar Interconnector andBusbar Reactor Switchgear, excluding power station auxiliaries, shall be as follows:-

A13.3.1 Switchgear provided for coupling Front and Rear busbars shall be named BUS COUPLER precededby the nominal busbar voltage followed by the section number(s).

eg 11 kV Bus Coupler 3


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A13.3.2 Switchgear provided for sectioning Front or Rear busbars shall be named BUS SECTION preceded bythe nominal busbar voltage and identification and followed by the adjacent section numbers.

eg 33 kV Front Bus Section 2

A13.3.3 Switchgear provided for connecting remote sections of a busbar shall be named INTERCONNECTORpreceded by the nominal voltage and followed first by the busbar number(s) adjacent to the switchgearand then by the busbar number(s) at the remote end of the circuit.

eg 66 kV Interconnector 4/1

A13.3.4 Switchgear associated with a reactor circuit connecting sections of busbars shall be named REACTORINTERCONNECTOR, SECTION REACTOR, or TIE BAR REACTOR, preceded by the nominal busbarvoltage and followed by the busbar number(s) adjacent to the switchgear and then by the busbarnumber(s) at the remote end of the circuit.

eg 33 kV Reactor Interconnector 4/1

A13.4 Switchgear associated with generator circuits shall be named GENERATOR followed by the numberof the generator.

eg Generator 1

A13.5 Metal Enclosed Type Switchgear (Shuttered)

The shutters covering the contacts when the switchgear is withdrawn shall comply with the following:-

A13.5.1 Shutters covering contacts directly connected to busbars shall be coloured red and bear the identificationof the busbar in white lettering.

eg 33 kV FRONT BUSBAR 1

All other shutters shall be coloured yellow.

A13.5.2 For incoming feeder contacts the yellow shutters shall bear in red lettering the identification of the circuit.

A13.5.3 When more than one set of shutters associated with a particular circuit breaker are coloured yellow theyshall bear the designation of the equipment associated with the contacts which they cover.

A13.6 The implementation of the nomenclature given above under the heading "Metal Enclosed TypeSwitchgear", is illustrated in Diagram 6.

A14 HV DC SWITCHGEAR

A14.1 The nomenclature of DC switchgear shall be the designation and number of the associated equipmentfollowed by the function of the particular item of switchgear.

A14.2 The numbering of DC switchgear shall be in accordance with section A9.2 (numbering of 400 kVswitchgear) replacing the prefix 'X' by the letter 'D'.

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A15 NOMENCLATURE FOR SHORTING/DISCHARGE SWITCHES ASSOCIATED WITH STATICCAPACITORS, COMPENSATORS AND FILTERS.

A15.1 In general, switchgear numbering on static capacitor, compensator and filter circuits follows therequirements detailed in respect of nomenclature and also in the numbering of circuit breakers,disconnectors and earth switches. The numbering rules for shorting/discharge switches are as follows:

A15.2 Where switchgear used for shorting/discharge functions as a fully rated earth switch or maintenanceearth on all phases at all points of application then it should be numbered as an earth switch ormaintenance earth as appropriate. In all other cases the following numbering shall be applied:

A15.2.1 The first part shall be a number or letter(in the case of RSVC) to denote the circuit nomenclature.

A15.2.2 The second part shall be a letter to denote the type of circuit, i.e "C".

A15.2.3 The third part shall be the circuit sub-division reference as used on a banked circuit where appropriate.

A15.2.4 The fourth part shall be used, where necessary, for the numbering sequence for switchgear which wouldotherwise bear the same number.

eg For Static Capacitor 33C1, 3C23CA1, 3CA2 for Bank A

A15.3 The implementation of the information given above is illustrated in Diagrams 9 and 10.

A16 EARTHING SWITCHGEAR

A16.1 The numbering of permanent earthing switches should, as far as possible, be in accordance with thepreceding directives in sections A9-A15.

A16.1.1 Where more than one earthing switch qualifies for a particular number, then the number shall be suffixedby unique letters, and the provision of paragraphs A9.2.4 and A9.2.5 shall apply. In the case of busbarearthing switches such numbering should run from the end of the substation that is not designed to beextended or if a substation is to be extended in both directions, starting from some central or bus-sectioning point.

A16.1.2 Where two or more earthing switches are associated with a banked circuit which is already identifiedby use of a letter suffix, the earthing switches shall be furthered identified by use of an additional numbersuffix.

eg For circuit associated with 400 kV capacitor bank 1A earthing switches shall be X151A1, X151A2

A16.1.3 Where earthing switches are installed, which cannot be numbered in accordance with the directives insection A16.1.1 or A16.1.2 they shall be designated 'E' followed by a number. At a particular namedsite no number shall be duplicated.

A16.2 Where equipment is used which can perform the duties of both a disconnecter and earth switch thenthe earth part should be identified as the disconnecter followed by >ED=.

eg earthing device associated with IT4IT4ED.

A16.3 Where fixed maintenance earthing equipment (i.e. earthing equipment applied phase by phase) isinstalled, it shall be designated 'F' followed by a number. At a particular named site no number shallbe duplicated.

A16.4 Where a FAULT THROWER is fitted for the protection of a transformer, the nomenclature shall be asfollows:-


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A16.4.1 The designation and number of the associated transformer.

A16.4.2 The words FAULT THROWER.

eg Grid Transformer 1 Fault Thrower

A16.4.3 The identifying number shall consist of the prefix FT followed by the identification number of thetransformer.

eg FT2A for Grid Transformer 2A

A17 NEUTRAL EARTHING

A17.1 The nomenclature of neutral earthing switchgear shall be the designation and number of the associatedequipment followed by the words NEUTRAL EARTHING SWITCH.

A17.2 The numbering of neutral earthing switchgear, except in the case of common neutral earthingswitchgear, shall be the letter 'N' followed by a sequence number.

A17.3 The numbering of common neutral earthing switchgear shall be as follows:-

A17.3.1 The first part shall be a letter to denote the type of circuit with which the switchgear is associated asgiven below:-

M -GeneratorT -TransformerP -Petersen CoilS -SectionR -Neutral Resistor, Neutral Reactor or Neutral Earthing Point

A17.3.2 The second part shall be the number of the circuit.

A17.3.3 The third part shall be the letter N to denote the neutral earthing function.

A17.3.4 The fourth part shall be a sequence number, zero being reserved for neutral circuit breakers.

A17.4 The nomenclature of neutral earthing resistors shall be the designation and number of its associatedequipment followed by the words NEUTRAL EARTHING RESISTOR.

eg Sync Comp 5 Neutral Earthing Resistor

A17.4.1 Where the neutral earthing resistor is common to more than one item of equipment it shall bedesignated COMMON NEUTRAL EARTHING RESISTOR followed where appropriate by a uniquesequence number.

A17.5 The implementation of the information given above under the heading "Neutral Earthing Switchgear"is illustrated in Diagram 7 for certain arrangements.

A18 GAS ZONE NUMBERING

A18.1 Gas zone numbering associated with sulphur hexafluoride insulated Metal Enclosed switchgear will benumbered to associate with the relevant circuit following the switchgear numbering principles describedabove.

A18.2 Due to the diverse manufacturing types, specific numbering will be agreed on an individual substationbasis after consultation with Operational Services, System Management.

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A19 SPECIAL LAYOUTS

A19.1 Where, due to special layouts, direct application of this Procedure is impracticable, the numbering andnomenclature in line with the general principles embodied in the text shall be approved as follows:-

(a) by SM Operational Services, (for equipment owned and/or controlled by NGC).

(b) by SM Operational Services and the User Company Representative, (in the case of equipment not underthe direct operational control of the NGC).

A19.2 When extensions to substations, not envisaged at the design stage, are undertaken, special care shouldbe taken. Switchgear numbering on particular items of apparatus should not be swapped to tie in withnew sequences if it is thought that greater confusion could result.


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A20 ABBREVIATIONS

A20.1 To achieve a level of consistency in differing areas from alarm database management to acceptablelabelling sizes the following can be used as abbreviations for the various plant items. Where the use ofabbreviations could cause confusion eg safety related documents, their use should be limited.

TABLE 4

Plant Item Abbreviation

Auxiliary and Earthing Transformer AUX / E Tx

Auxiliary Transformer AUX Tx

Bus Coupler BC

Bus Section BS

Cable Sealing End CSE

Circuit Breaker CB

Combined VT / CT Unit VT/CT

Compensator Transformer COMP T

Current Transformer CT

Disconnector DISC

Earth Switch ESW

Earthing Transformer E Tx

Generator GEN

Generator Transformer GEN T

Inductor IND

Isolator ISOL

(Liquid) Neutral Earthing Resistor (L)NER

Main Busbar MBB

Mechanically Switched Capacitor MSC

Overhead Line OHL

Quadrature Booster QB

Reactor RCT

Relocatable Static Var Compensator RSVC

Reserve busbar RBB

Static Capacitor CAP

Static Var Compensator SVC

Station Transformer STN T

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Super Gird Transformer SGT

Switch Disconnector SW DISC

Synchronous Compensator SYNC COMP

Thyristor Switched Capacitor TSC

Thyristor Switched Reactor TSR

Voltage Transformer / Capacitor VT / Wound VT VT / CVT / WVT

TABLE 5SWITCHGEAR NUMBERING AND NOMENCLATURE

(Excluding LV Metal Enclosed)

CLASS TITLE SYMBOLS

400 kV 275 kV 132 kV L.VLines Switch Disconnector X*00 L*0 *00 *L0

Line Earth Switching X*01 L*1 *01 *L1By-Pass Disconnector X*02 L*2 *02 *L2Line Disconnector X*03 L*3 *03 *L3Main Busbar Selector Disconnector X*04 L*4 *04 *L4Circuit Breaker X*05 L*5 *05 *L5Reserve Busbar Selector Disconnector X*06 L*6 *06 *L6Circuit Breaker Disconnector (Busbar Side) X*07 L*7 *07 *L7

Transformer High Transformer Circuit Breaker X*10 H*0 *10 *H0Voltage Side Transformer Earthing Switch X*11 H*1 *11 *H1

Transformer By-Pass Disconnector X*12 H*2 *12 *H2

Transformer Disconnector X*13 H*3 *13 *H3Main Busbar Selector Disconnector X*14 H*4 *14 *H4Switch Disconnector X*15 H*5 *15 *H5Reserve Busbar Selector Disconnector X*16 H*6 *16 *H6

Main Bus Section Main Bus Section Circuit Breaker X*20 S*0 *20 *S0

Main Bus Section Earthing Switch X*21 S*1 *21 *S1Main Bus Section Disconnector (No. 1Side)

X*24 S*4 *24 *S4

Switch Disconnector X*25 S*5 *25 *S5Mesh Opening Corner Disconnector X*26 S*6 *26 *S6Main Bus Section Disconnector (No. 2Side)

X*28 S*8 *28 *S8

Reserve Bus Reserve Bus Section Circuit Breaker X*60 P*0 *60 *P0

Section Reserve Bus Section Earthing Switch X*61 P*1 *61 *P1Reserve Bus Section Disconnection (No.1Side)

X*66 P*6 *66 *P6

Reserve Bus Section Disconnector (No.Side)

X*69 P*9 *69 *P9


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Bus Coupler Bus Coupler Circuit Breaker X*30 W*0 *30 *W0Bus Coupler Earthing Switch X*31 W*1 *31 *W1Bus Coupler Main Busbar Disconnector X*34 W*4 *34 *W4

Bus Coupler Reserve BusbarDisconnector

X*36 W *6 *36 *W6

Quad Booster Reactor Circuit Breaker X*40 R*0 *40 *R0Reactor Earthing Switch X*41 R*1 *41 *R1

Line Disconnector X*43 R*3 *43 *R3

Main Busbar Selector Disconnector (1stchoice)

X*44 R*4 *44 *R4

2nd Reactor Circuit Breaker where 2 perReactor

X*45 R*5 *45 *R5

Reserve Busbar Selector Disconnector (1stChoice)

X*46 R*6 *46 *R6

Circuit Breaker Disconnector (BusbarSide)

X*47 R*7 *47 *R7

Main Busbar Selector Disconnector (2ndChoice)

X*48 R*8 *48 *R8

Reactor Tie Busbar Disconnector orReserve Busbar Selector Disconnector(2nd Choice)

X*49 R*9 *49 *R9

Static Shunt Reactor/Capacitor Circuit Breaker X*50 *0 *50 *K0Compensator Reactor/Capacitor Earthing Switch X*51 *1 *51 *K1

Reactor/Capacitor Disconnector X*53 *3 *53 *K3

Reactor/Capacitor Switch Disconnector X*55 *5 *55 *K5Transformer Low Transformer Circuit Breaker T*0 *80 *T0Voltage Side Transformer Earthing Switch T*1 *81 *T1

Transformer Disconnector T*3 *83 *T3

Main Busbar Selector Disconnector T*4 *84 *T4Switch Disconnector T*5 *85 *T5Reserve Busbar Selector Disconnector T*6 *86 *T6

Generators Generator Circuit Breaker. (Where 2 pergenerator, Main Busbar)

X*90 M*0 *90 *M0

Generator Transformer Earthing Switch X*91 M*1 *91 *M1By-Pass Disconnector X*92 M*2 *92 *M2Generator Transformer Disconnector X*93 M*3 *93 *M3Main Busbar Selector Disconnector X*94 M*4 *94 *M4

Generator Circuit Breaker where 2 pergenerator (Reserve Busbar) or SwitchDisconnector

X*95 M*5 *95 *M5

Reserve Busbar Selector Disconnector X*96 M*6 *96 *M6Circuit Breaker Disconnector (Busbar Side) X*97 M*7 *97 *M7

SynchronousCompensators

Synchronous Compensator - 'Main CircuitBreaker'

*M01

Synchronous Compensator - 'Starting'Circuit Breaker

*M02

Synchronous Compensator - 'Running'Circuit Breaker

*M03

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Synchronous Compensator Disconnector *M3Synchronous Compensator EarthingSwitch

*M1

MiscellaneousEquipment

Disconnector Associated with certainmiscellaneous auxiliary equipment e.g VT's

*A3

Fault Thrower FT*

*Denotes sequence of switch groups

Excluding Supergrid and Grid Transformer Circuit feeding a Bulk Supply Point. These circuit breakers do not havea number but should be respectively identified as Supergrid* and Grid*

SEE DIAGRAMS 1 - 11 FOR ILLUSTRATIONS OF BOTH NUMBERING AND NOMENCLATURE


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