National Grid Design Handbook dh01

7/25/2019 National Grid Design Handbook dh01

1/26

Construction

Design Handbook

APPLICATION GUIDANCE NOTES FOR THE ASSET REPLACEMENT OFTRANSMISSION SYSTEM PROTECTION AND CONTROL EQUIPMENT

DH 01

Issue 2

Author ised by:

Technical Assurance Manager

Date:

29th

June 2007


2/26

DH 01 Issue 2June 2007

Page 2 of 26

This page is intentionally blank


3/26


Page 3 of 26

APPLICATION GUIDANCE NOTES FOR THE ASSET REPLACEMENT OF TRANSMISSIONSYSTEM PROTECTION AND CONTROL EQUIPMENT

Contents

1. Purpose 4

2. References 4

3. Responsibilities 4

4. Introduction 4

5. Relay Equipment Buildings and General Site Arrangements 7

6. Feeder Main Protection 8

7. Supergrid Transformer Protection 10

8. Shunt Reactor Tertiary and Earthing Transformer Protection 11

9. Mesh Corner Protection 11

10. Busbar Protection 12

11. Circuit Breaker Fail Protection 12

12. Bus Section & Bus Coupler Protection 13

13. Circuit Breaker Relay Panels 13

14. Fault Recorders 13

15. Delayed Auto Reclose 14

16. Ferroresonance Protection 15

17. Capacitor Voltage Transformers & Power Line Carrier Coupling Equipment 15

18. Substation Clock & Distribution of Timing 16

19. 110V DC & 48V DC Supplies 17

20. 415V LVAC Supplies 17

21. Synchronising & Voltage Selection 17

22. Information Management Unit (IMU) 18

23. Supervision 18

24. Testing Facilities 19

25. Control Systems 19

26. Circuit Breaker Replacement 22

27 Authorisation/Revision 23

Appendix 1 Emergency Close Requirements on Legacy SCSs 24

Appendix 2 Removal of Existing Power Line Carrier Equipment 25


4/26


5/26


Page 5 of 26

To facilitate the calculation and issue of Protection Settings, relay details (type, range, rating etc.)need to be included or issued, two months after the design freeze stage.

Relay calculations shall be submitted to National Grid at least 20 weeks ahead of the circuitcommissioning date to facilitate the issue of Thermal Rating data. All information should besubmitted in line with the timescales outlined in UKBP/TP106(E) & UKBP/TP107(E).

The supplier prior to the FAT shall apply all programmable software logic settings and powersystem settings to the equipment. The relay settings calculationsshall be submitted to and agreedwith National Grid prior to the commencement of the FAT. The process for managing numericalrelays is detailed in Commissioning Handbook 21, Management of Numerical Protection Schemes.

To facilitate the control system configuration, the Generic Equipment Model (GEM) informationshould be submitted and agreed prior to the design freeze stage.

4.2.2 Drawings

To clarify and confirm the protection design the following diagrams must either be included withinor appended to the Design Intent Document (DID):

Main Connections and Protection key diagram.

Drawing showing the distribution of functions within a set of IEDs.

4.2.3 Tripping Arrangements

Current practises in tripping arrangements are such that only one self resetting trip relay pertripping coil/system is used. All functions in a bay solution shall initiate a single trip relay per circuitbreaker trip system which shall then be used in the trip circuit, to minimise trip circuit supervisionwiring. For protection tripping functions there shall be no more than one trip relay between theprotection and the trip coil. This philosophy should be adopted as standard where the scope ofwork allows.

4.2.4 Reduced Equipment

Bay solutions using numerical relays shall be employed. Where protection systems include anintegral intertrip facility, this shall be used to supplement the standard requirements for the type ofconnection. Alarm, Indication and Control cabling to the Control function should utilise serial

connections where possible. This may be achieved with the use of appropriate protocol converters.The distribution of facilities across equipment in the system shall comply with TS 2.24 and the TS3.24 series of technical specifications.

4.2.5 Plant Protection

Preference will be given to the use of modern numerical protection with acceptable diagnosticfacilities to allow a 1 out of 1 protection to be applied.

For auto transformers the use of a restricted earth fault using external high impedance componentsis not required. However where REF is a discrete low impedance algorithm in the overall protectionrelay then it shall be enabled.

4.2.6 Setting Resistors

Where required circulating current protection Stabilising Resistors shall be replaced with ones of aspecific fixed value as determined by the particular application. It is not permissible to use variableresistors.

4.2.7 Commissioning

Commissioning shall be in line with UKBP/TP106(E). Maximum use of Factory testing should beconsidered to reduce on-site commissioning time. The proposed commissioning philosophy andmethodology shall be included within the DID.


6/26


Page 6 of 26

4.2.8 Temporary Protections

The supplier shall make provision for engineering that will enable temporary commissioningprotection to be installed and commissioned. The supplier must also provide, install and removewhen finished with any temporary protections required to meet any Emergency Return To Service(ERTS) requirements and for stage 2 commissioning works.

4.2.9 Trip Circuit Wiring

The supplier must supply calculations and carry out site testing that demonstrates that the circuitbreaker close and trip coils will reliably operate with a minimum of 87.5V across the coil. Thefollowing points must be taken into consideration:

The formal calculations which are to be submitted for client review must be listed within theDID. This list should include calculation reports for the CB trip and close circuitry of all existingand new Circuit Breakers which are being worked on.

Post Design Freeze the supplier shall submit the calculations for review by National Grid.These calculations should demonstrate that the CB trip and close coils receive sufficientvoltage for reliable operation i.e. a minimum of 87.5V. This is under minimum battery conditionsat the battery terminals as stated in TS 3.12.4 (93V for dispersed relay rooms and 102V forCentral Relay Rooms). The maximum trip and close wiring resistance in series with the trip andclose coils will form part of these calculations. This calculation must be from the contactfurthest away from the coil being considered.

During installation and Stage 1 commissioning, SCT 01 and SCT 26 (or the Suppliersapproved equivalents which must incorporate fully the requirements of SCT 01 & SCT 26)shall be completed in full. This will confirm that the trip and close circuits conform to theproposed design.

SCT 01 requires a check that the trip coil operates at 87.5Volts using a trip coil tester. Thesetesters are normally used by Asset Management staff during maintenance and the latest onesmanufactured by RES Ltd use the Substation battery as a source of supply and have aconstant voltage output variable from 5 - 95% of the input voltage. These can be used forsetting the source voltage to either 102V or 93V in a safe and controlled manner thusrepresenting the minimum battery state after 6 hours.

SCT 26 requires a trip to the CB fromALLinitiating contacts and must be adhered to. It alsorequires instantaneous volt drop measurements across the trip wiring and trip coil with suitableUV trace recorders or storage scopes connected. This test is at normal battery voltage (125V)but should be repeated at the minimum 6 hour value (93V or 102V) and in both cases thevoltage across the trip coil must not be less than 87.5V.

SCT 26 also refers to Transmission Design Memorandum 3/35 Site Tests to ConfirmSatisfactory Operation of Circuit Breaker Trip Coils, and provides guidance on therequirements to be met or which can be accepted for existing installations.

4.2.10 Use of Opto Isolated Inputs on Modern Relays

The majority of modern IEDs make use of opto-isolated status inputs. Due to the very low burdenof this type of status input they are particularly vulnerable to inadvertent operation by inducedvoltages on the wires/cables they are connected to. The supplier must ensure that suitableprecautions are taken to ensure that all IED status inputs are not vulnerable to operation byinduced voltages and that the requirements of TS 3.24.4, clauses 4.42 & 43 are fully met.

Where possible status inputs should not be energised by contacts connected to long runs of cable,particularly ones running adjacent to power cables or between substations (i.e. HV & LV sites). Ifunavoidable suitable measures must be taken such as fitting loading resistors to the status inputsor using interposing relays to isolate them.

Where double pole switching is utilised, drain resistors must not be fitted across the contactsswitching the negative side of the supply.


7/26


Page 7 of 26

5. RELAY EQUIPMENT BUILDINGSAND GENERAL SITE ARRANGEMENTS

5.1 Present Status

All relay equipment buildings are in reasonable condition. Some substations employ a centralisedrelay room with others utilising dispersed type relay rooms. In both cases there are varyingamounts of spare capacity for new equipment.

5.2 Objectives

To maximise pre-outage work, reduce the risk on delivery during outages by installing equipmentand cabling and site function testing all prior to the outage.

This can be effected by use of existing relay room spare capacity where possible. If no sparecapacity exists consideration should be given to utilising other spare accommodation on site, relayroom extensions or a pre-fabricated / portable relay room.

Guidance will be given, if required, at the tender stage although equipment location will dependupon current and future proposed works.

Total replacement of light current equipment will require new accommodation with cabling direct tothe plant marshalling kiosks.

Piecemeal replacement may reuse existing accommodation and cables but the extent of reuse willdepend on outage and Emergency Return to Service (ERTS) time constraints.

5.2.1 Dispersed Relay Rooms

At sites with dispersed relay rooms, a total replacement of protection and control equipment usinga 19" mounting arrangement is preferred. New swing rack cubicles meeting IP50 atmosphericprotection rating should replace existing swing frames. Retain the terminal marshalling racks andrefurbish where old larger terminal blocks are used. Modern terminal blocks are smaller and willincrease the space for additional terminations.

Any distributed high impedance busbar protection relays should be retained unchanged along withback tripping relays where possible.

The re-use of any existing modern electronic relays will be highlighted in the enquiry document.

5.2.2 Central ised Relay Rooms

At sites with a centralised relay room, a total replacement of protection and control equipmentusing a 19" mounting arrangement is preferred. New swing frame cubicles meeting IP50atmospheric protection rating should replace existing TPS 6/12 swing frames. Where it is not costeffective or there are outage constraints then to avoid re-cabling, arrangement can be made to re-use the existing back boxes. In this case retain the terminal marshalling racks and refurbish whereold larger terminal blocks are used. Modern terminal blocks are smaller and will increase the spacefor additional terminations.

Where relay panels are removed their associated back boxes must be cleared of all terminals,wiring and cabling. Redundant back boxes must not be used as marshalling points.

The re-use of any existing modern electronic or numeric relays will be highlighted in the enquirydocument.

5.2.3 Cabling

Over filling the existing cable trenches should be avoided. New cables should not prevent theremoval of redundant cables in the future. Also, redundant cables should be removed from thecable trenches inside buildings and within 10 metres of building entries and marshalling kiosks andother plant termination points.


8/26


Page 8 of 26

The condition of any multicore cables must be assessed to ensure they are suitable for re use. Inparticular where cables are clamped or cleated the area around and under the clamp or cleat mustbe inspected to ensure there is no damage to the cable. Cables that have V.I.R. insulation or thosethat are unsuitable and/or unsound should be replaced.

For new installations consideration must also be given to segregation of signals between multicorecables. As a minimum the following signals should be allocated to separate cables:

240/415V AC supplies.

110V DC supplies.

48V DC supplies.

First and second supplies must also be run in separate cables.

CT connections.

VT connections.

DC trip, alarm, control, & interlocking signals can be allocated to the same cable but firstand second tripping systems must be run in separate cables.

Transducer mA output signals. These must also be allocated to screened twisted paircable.

Where signals are being sent between different sites, for example between the HV and LV sides oftransformers the first and second trip systems must be allocated to separate cables. Ideally thesecables should be physically separated by at least 5 meters to prevent accidental damage to both

and be run in separate ducts/trenches from any parallel power cables.

Fibre Optic interconnections, supplied by the Contractor, are preferred between dispersedequipment locations to provide electrical isolation and noise immunity.

Fibre optic cabling shall be installed and protected to the applicable TS.

6. FEEDER PROTECTION

6.1 Feeder Main Protection

6.1.1 Present Status

Feeder first and second main protections are generally a mix of original electro-mechanical relays,

hard wired; modern electronic relays, hard wired and modern electronic relays wired to 19"mounting arrangement.

6.1.2 Objectives

To completely replace the feeder main protection equipment within the relay room with TS 2.24designed equipment 125VDC versions now being the standard. Any existing modern electronicrelays that are considered serviceable should be recovered and returned to National Grid stores tosupport the availability of the system. Guidance will be given during the design stage of thecontract as to any EMIs (TDCs) that may be relevant to the latest equipment.

Remote (ENCC or SCP) protection IN/OUT switching is not required on new installations unlessrequired as a function of unlocking a protection as a result of communication failures. On SCS onlyinstallations where protection IN/OUT switching exists these facilities should be migrated to thenew SCS. It shall only be added to protections that require the comms unlocking functionality.However each main protection should be fitted with a test / normal switch to enable all its outputsto be isolated.

6.1.3 Non Unit blocked overreach distance protection

National Grids preferred arrangement is that where non-unit distance protection with integralcommunications is being installed it should be configured as a blocked overreach scheme if thesignalling between ends allows and the scheme is available within the equipment.


9/26


Page 9 of 26

In the event of blocking channel failure the protection should automatically revert to plain distance.No blocking In/Out controls would be required in this instance.

An additional alarm should be raised from each end IED (1837 1ST

BLOCK CHNL or 1859 2nd

BLOCK CHNL Flty/Hlthy).

6.1.4 Zone 2 override

Where blocked overreach distance protection cannot be fitted a switchable facility allowing forinstantaneous zone 2 reach shall be provided on all plain distance protections on all bay solutions.

This shall be named "Zone 2 Override" and shall allow DAR in all cases. The requirement can bemet by either overriding the zone 2 timer and causing an instantaneous zone 2 trip output withoutDAR lockout, or by extending the zone 1 reach to a setting group which shall be set to the normalzone 2 reach setting.

Remote In/Out switching of the above (to ENCC) shall be provided at the source end of any circuitconfiguration where an SGT could remain on load fed from that substation. This does not include 4switch mesh configurations. Transformer feeders where the remote zone 1 reach normally extendsinto the transformer impedance do not require this remote facility.

6.1.5 GPS Timed Differential Protection

Separate GPS clocks and aerials should be provided for each GPS timed differential protectionsupplied. It is not permissible for relays located on different circuits to share the timing signal fromone clock. Where a double unit protection arrangement is provided on a circuit each unit protectionmust have its own clock.

The siting of GPS aerials shall be verified by a GPS survey. Installed equipment shall be monitoredfor a period of not less than one month to confirm GPS integrity.

All aerials and associated receivers shall be clearly labelled with the circuit and function beingsupported. In addition the aerial installation must be suitably guarded to prevent interference bypersonnel.

6.2 Feeder Intertripping & Protection Signalling


A mix of old and modern intertripping equipment and there associated protection interfaces.

6.2.2 Objectives

To replace any old intertrip equipment, protection-signalling equipment and associated interfaces.Where possible use should be made of integrated intertripping and protection signalling facilities.See 4.2.4 above. Where possible equipment utilising digital rather than analogue circuits shouldbe fitted. Fibre Optic cabling should be used for cross-site transmission where possible. The fibreoptic interface unit will need to be located as close to the Cable & Wireless (C & W) Service aspossible.

Test facilities shall be provided in line with the TS requirements.

Note:

Transformer disconnectors operating in the fault interfering mode require current andvoltage interlocks to be fitted following the addition of a second intertrip channel.

Power Line Carrier (PLC) intertripping equipment should be located adjacent to the circuitrelay panels. Standalone intertripping equipment that connects to the C & W service shouldbe located in the telecommunications room.

If the carrier equipment is not to be used consideration on the method and cost of removalshould be highlighted during the design stage.


10/26


Page 10 of 26

Operating frequencies and codes for dedicated intertripping equipment need to beconfirmed with National Grid.

6.3 Feeder Common Protection


Feeder common protections (e.g.: system back-up, trip relay reset, overload and phases

unbalanced alarms etc.) are generally a mix of original electro mechanical relays, modernelectronic relays and modern electronic relays wired to 19" mounting arrangement.

There is an array of secondary bypass systems currently installed tailored to specific sitearrangements or requirements. I.e. circuit breaker bypass schemes.

6.3.2 Objectives

Replace with TS 2.24 designed equipment 125VDC versions now being the standard. Overloadalarm relays do not require replacing. Other considerations are outlined in 4.2.4 above.

Depending on the usage/usefulness remove secondary bypass arrangements where installed andreplace with new systems as detailed.

7. SUPERGRID TRANSFORMER PROTECTION

7.1 Present Status

A typical relay room houses the following relay panels

SGT Overall Protection.

SGT HV Protection.

SGT LV Protection (Located with LV relay equipment).

Transformer End Protection (where there is an operational need to back energise).

HV Connections Protection.

LV Connections Protection.

The equipment is generally a mix of original electro mechanical relays, modern electronic relays

and modern electronic relays using a 19" mounting arrangement. Traditionally, SGT LV equipmenthas been housed within Distribution Network Operator (DNO) buildings.

7.2 Objectives

To completely replace with TS 2.24 designed equipment 125VDC versions now being the standard.The location of the SGT LV protection panel (i.e. on National Grid or DNO premises) should bediscussed & agreed with National Grid prior to the agreement of the DID.

With any circulating current protection, a calculated performance report will must be prepared bythe Contractor before equipment is ordered, to allow the correct value and thermal rating of anyresistor, Metrosil and relay range and setting values to be determined (See PS(T)010). Informationto produce calculated performance reports should be collected during the site visits and included inthe contract stage DID.

Other considerations are outlined in 4.2.4 above.

7.3 Back up Protection Settings at Operational Interfaces

Following a number of National Grid internal reviews various issues surrounding the application ofback up protection settings have been highlighted.

The main concern is grading with downstream DNO back up protection with the followingfunctions:-


11/26


Page 11 of 26

SGT HV 2 stage Overcurrent

SGT LV Overcurrent (where applied)

SGT LV Earth Fault

SGT Standby Earth Fault on double wound transformers (sometimes known asunrestricted earth fault)

The approach that should be followed is: -

1. Review the existing setting and calculate the existing operate time. This review should takedue cognisance of the type and characteristic of the old relay.2. Using the new current setting (amps) as per policy calculate a new setting based on the

operate time from 1.3. Using the highest Overcurrent and Earth Fault setting from interface user (DNO or Genco)

ensure positive discrimination (at least 400ms) between proposed setting and interfacesetting and a clearance time of less than 2.4 seconds.

4. Refer any inconsistencies back to National Grid for further investigation.

National Grid will make available both the existing settings and the highest interface user setting atsites where transformer protection replacements are planned. Please request this information if it isnot forthcoming.

8. SHUNT REACTOR - TERTIARY AND EARTHING TRANSFORMER PROTECTION

8.1 Present Status

At some sites shunt reactors have been connected to the 13kV tertiary winding of some SupergridTransformers or in some cases direct to the HV busbars. In these instances, the brick buildinghousing the associated Shunt Reactor Protection Relay Panel and the Tertiary and EarthingTransformer Protection Relay Panel are at best damp and at worst have rainwater leaking in.

8.2 Objectives

To locate new relay panels with TS 2.24 designed equipment in the vicinity of the existingSupergrid Transformer Relay Panels (i.e. Centralised Relay Room or Dispersed Relay Room).Repair or protect the fabric of existing cubicles so they may be retained as marshalling cubicles,

i.e. retain existing cabling and provide new multicore cables to the new location of the new relaypanels.

With any circulating current protection, a calculated performance report will need to be prepared bythe Contractor before equipment is ordered, to allow the correct value and thermal rating of anyresistor, Metrosil and relay range and setting values to be determined (See PS(T)010). Informationto produce calculated performance reports should be collected during the site visits and included inthe contract stage DID.


9. MESH CORNER PROTECTION

9.1 Present Status

A typical relay room houses relay panels containing Mesh Corner Protection - Original electromechanical relays hard-wired.

9.2 Objectives

To replace with TS 2.24 designed equipment 125VDC versions now being the standard. MeshCorner Protection should be installed as part of the integrated suite of panels pre-outage. FeederEnd Protection will be included as a matter of course and may be contained within Mesh cornerand/or feeder protection.


12/26


Page 12 of 26

Where numerical mesh corner protection is being installed the use of disconnector auxiliaryswitches in the current transformer ac circuitry must be avoided. Busbar replicas should be formedinternally within the equipment using digital inputs to indicate the plant position to the mesh cornerprotection.

10. BUSBAR PROTECTION

10.1 Present Status

a) Centralised Relay Room Arrangement.Busbar Protection A - Installed when substation commissioned.Busbar Protection B - Added later in 1970's.

Both A & B Protections are electro mechanical relays hard wired.

b) Dispersed Relay Room Arrangement.Original electro mechanical relays hard-wired. Relays for each circuit located in therespective dispersed relay room. Bus Section dispersed relay room houses additionalCommon Busbar Protection.

10.2 Objectives

Busbar protection will only be replaced where a full Site light current equipment replacement isundertaken or the extent of the work justifies a full system replacement. Where it has beendetermined necessary to replace the busbar protection the methodology will be as follows:

a) Centralised Relay Room Arrangement.To install, pre-outage, complete Busbar Protection with TS 2.24 designed equipment.

b) Dispersed Relay Room Arrangement.To replace with TS 2.24 designed equipment with distributed bay units located in eachblockhouse

c) Commissioning Handbook No. 24, Commissioning of Numerical Busbar Protection givesdetails of some of the issues which must be considered when installing and extendingnumerical busbar protection systems.

The complete methodology to engineer the replacement of the busbar protection and theinstallation stages should be clearly outlined in the DID.

At double busbar substations when the work is restricted to refurbishment of a circuit only thecurrent check & timer relays should be replaced. The back tripping relays should be left in situ. Allnecessary links etc should also be provided.

Where numerical busbar protection is being installed the use of disconnector auxiliary switches inthe current transformer ac circuitry must be avoided. Busbar replicas should be formed internallywithin the equipment using digital inputs to indicate the plant position to the busbar protection.

Where the substation busbar protection is being replaced in its entirety the Circuit Beaker Failfunctionality should be migrated into the new numerical busbar protection.

11. CIRCUIT BREAKER FAIL PROTECTION

11.1 Present Status

Most Circuit Breaker Fail protection equipment was added in the late 1970's and is in reasonablecondition. These relays are electronic & electro mechanical type hard wired.


13/26


Page 13 of 26

11.2 Objectives

Circuit Breaker Fail Protection will only be replaced where a full Site light current equipmentreplacement is undertaken or the extent of the work justifies a full system replacement. Where ithas been determined necessary to replace the circuit breaker fail protection the methodology willbe as follows:

Centralised Relay Room Arrangement and Dispersed Relay Room Arrangement:

To replace CBF relays with TS 2.24 designed equipment where the work is restricted to feederreplacement for that circuit at the time of the feeder outage. When the protection fitted to a circuitwithin a double busbar substation is being replaced the current check and timer relay functionsshould be migrated into the new IEDs and connected into the existing back tripping system.

Note: Some modern busbar protections have CBF included in their systems. Other considerationsare outlined in 4.2.4 above.

12. BUS SECTION & BUS COUPLER PROTECTION

12.1 Present Status

Bus Section Protection equipment is generally a mix of original electro mechanical relays hard

wired, modern electronic relays hard wired and modern electronic relays wired to 19" mountingarrangement. The existence of Commissioning Overcurrent protection on Bus Section circuitsneeds to be determined at the site visit, as the installation programme has been inconsistent. Meshcircuit breakers are considered to be Bus Section breakers in this context.

12.2 Objectives

To completely replace the protection equipment within the relay room with equipped with TS 2.24designed equipment. Also, add Commissioning Overcurrent protection to 19" mountingarrangement.

Commissioning overcurrent shall be installed with local (panel mounted) IN/OUT switching.Software or internal logic selection of Commissioning Overcurrent relays is not acceptable.

13. CIRCUIT BREAKER RELAY PANELS

13.1 Present Status

Circuit breaker relay equipment is generally original electro-mechanical relays hard wired.

13.2 Objectives

To replace with NGTS 2.24 designed equipment.

The contractor must be aware of the rating and suitability of the output contacts of circuit breakercontrol relays in view of the wide range of CB control schemes and CB close coil ratings. Otherconsiderations are outlined in 4.2.4 above.

14. FAULT RECORDERS

14.1 Present Status

Dedicated fault recorders are installed on the majority of 400 & 275kV feeder circuits.

14.2 Objectives

Replace with NGTS 2.24 designed equipment. Generally the integral fault recording and eventlogging facilities within equipment forming part of Standard Bay Solutions should be utilised.Dedicated standalone fault recorders are not required unless specifically specified by National Grid.


14/26


Page 14 of 26

Where removal of feeder monitoring from a fault recorder leaves only bus coupler, section andSGT inputs on the recorder these should be transferred to spare inputs on other existing faultrecorders on site and the recorder removed. The recorder should not be left in situ with a limitednumber of inputs. Where no existing fault recorders are available, the circuit fault recorder shall berelocated in a suitable relay room (such as the Bus Section) and the coupler, section and SGTinputs reconnected. This can also be used for future refurbishments on other feeder bays. Analternative is to use spare fault recorder trigger inputs on the new IEDs as long as the IED has timesynchronisation via a GPS signal in this case it is acceptable to dispense with monitoringtransformer neutral current.

Note: A C & W circuit may be required for a connection to an on-site IMU (if required). Sites withintegrated system monitor requirements (ISM) are specified separately and are to be installed withfacilities independent from the fault recorder.

Integrated functionality of protection relays shall be used as fault recorders where they meet theNGTS requirements and the information can be presented at the IMU (if installed). Therequirements are detailed in TS 3.24.71.

Remote fault recorder event extraction is normally provided via the IMU. For sites where there is noIMU then no remote fault record extraction shall be provided.

15. DELAYED AUTO RECLOSE

15.1 Present Status

Original electro mechanical relays, hard wired.

15.2 Objectives

a) Double Busbar Substation.

To replace Delayed Auto Reclose (DAR) with TS 2.24 designed equipment on a per circuitbasis at the time of a feeder outage. The DAR relay will have integral synchronising facilitiesthat will replace the existing site facilities. This relay will carry out both the manual andautomatic synchronising.

b) Mesh Substation.

To install, pre-outage, complete mesh substation Delayed Auto Reclose with TS 2.24designed equipment.

The transfer of DAR to the new equipment can be done by either taking a complete site DARoutage or transferring each mesh corner from existing to new Delayed Auto Reclose on aper mesh corner basis during short consecutive mesh corner outages.

This is site dependent and the site status is identified in the Substation Design Specification.

The supplier must be aware of the rating and suitability of the output contacts of circuitbreaker control relays in view of the wide range of CB control schemes and CB close coilratings.

The DAR interlocking facility (Trip Relay Reset) should be considered and novel solutionsoffered to emulate this functionality.

The DAR facility should include DAR synchronising, auto isolation, LV DAR andferroresonance where possible to simplify and reduce the interfacing requirements.Consideration should also be given to the use of solutions that utilise information availablefrom other equipment such as the SCS to achieve the DAR functionality.

The existing manual synchronising arrangements should be left in place.


15/26


Page 15 of 26

16. FERRORESONANCE PROTECTION

16.1 Present Status

A mix of CEGB SW Region designed equipment and early GEC designed equipment hard wired.

16.2 Objectives

To replace this equipment with TS 2.24 designed equipment.

All mesh corners with a transformer connected and a feeder having the ability to ferroresonate withthat transformer (or other arrangements with plant connected to the line and the feeder is on adouble circuit tower line), require as a minimum a Ferroresonance alarm facility.

Where the feeder is > 10 km in length further measures are required to either lock out the DAR orquench the ferroresonance:-

The preferred method is an F4 scheme. Suitable earth switches will probably not beavailable on protection refurbishment schemes. This method should therefore only beimplemented on switchgear contracts unless otherwise advised by National Grid.

For protection or DAR refurbishment on 275kV sites, an F2B scheme should be providedas the default option with the provision for an upgrade to an F3 scheme via a settingchange (assuming auto operation of SGT HV disconnectors is controlled by the DAR unit).

For protection or DAR refurbishment on 400kV sites, an F3 scheme should be provided asthe default with the provision for downgrade to an F2B scheme via a setting change.

The above mentioned setting changes are dependent on the design quenching capabilities of thedisconnector. For information on scheme description see TS 3.24.17, TS 3.24.80 & TGN(E)086.

17. CAPACITOR VOLTAGE TRANSFORMERS & POWER LINE CARRIER COUPLINGEQUIPMENT

17.1 Present Status

400kV line traps are generally in good condition.

275kV line traps may require refurbishing viz.: -

Condition of varnish on end sheets

Is casting single or double door type

Condition of tuning capacitors within line traps

Many coupling equipments were installed at the time of the original installation and may bedeteriorating in a hostile environment.

Determine type and condition of co-axial cable. CVT fuse boxes and CVT marshalling kiosks maybe deteriorating in a hostile environment. Original Anaconda connection between the couplingequipment and CVT may be deteriorating in a hostile environment. High frequency earthing maynot exist or if installed not always be to the required specification. EMIs (TDCs) may need carryingout to increase the burden on the CVTs.

In general, for all line traps, the requirements of drawing 95/52182 shall be carried out.

17.2 Objectives

If specified in the contract replace all secondary equipment on a like for like basis with modernintegrated and type registered units.

400kV line traps - Refurbish as necessary, or replace with a new line trap.


16/26


Page 16 of 26

275kV line traps - Refurbish as necessary, or replace with a new line trap.Note: A Casting base with double doors is essential if a wide band unit is a requirement.

Replace old AEI, EEC or GEC original coupling units with equivalent equipment.To replace co-axial cable if not to the latest specification and replace CVT fuse boxes and CVTmarshalling kiosks if deteriorating due to hostile environment.

Replace Anaconda connection with modern equivalent if coupling equipment is changed. Add highfrequency earthing if none fitted or modify if not to the required specification.

CVT burden resistors must be added in line with the relevant TDCs to prevent Ferroresonance andpre-load it to at least 50% of rating on old style CVTs in order to improve accuracy.

17.3 High Frequency Earth ing/Corona Rings

Where Line Traps are being removed as a consequence of protection refurbishment, theirassociated line coupling equipment and tuning inductor must also be removed. Earth bars shouldreplace the tuning inductor and make the final connection to earth, providing earth continuity to thesecondary side of the CVT. The requirements are detailed in TGN(T)18 & TDC 255.

The photographs in Appendix 2 illustrate the requirements, although reference must be made toTGN(T)18 for further details. These show a link being added to short out the tuning inductorconnections, and a final earth connection being made where the coupling equipment is normally

connected. Failure to fit these earth bars could result in catastrophic failure of the CVT.

Where line traps are being removed the busbars shall be made good and ancillary itemssuch corona rings shall be fitted. All three VTs shall be left with the same primaryconnections.

Further to this on circuits where this work is being carried out, all CVTs should be fitted with HighFrequency earthing where it is not installed already.

These issues must be raised as a point for discussion at the commissioning panel and noted withinthe minutes.

18. SUBSTATION CLOCK & DISTRIBUTION OF TIMING

18.1 Present Status

Equipment currently installed supports transmission timing from the MSF signal (ex Rugby source).It is distributed using serial transmission to the onsite SCS or METRO, the OMS (PE) whereinstalled and provides clean contact half-hour timing pulses to other equipment such as faultrecorders. The aerial for the radio clock is fitted internally or externally near the telecomms room.

18.2 Objectives

Where identified the equipment is to be replaced with TS 2.24 designed equipment. This willprovide a timing source synchronised to GPS. GPS aerials require line of site to the sky and needto be fitted externally. The supplier must carry out a survey to ensure that the aerial can locatesignals from sufficient satellites.Other considerations are outlined in 4.2.4 above.

For total site refurbishment of light current equipment the preference is for all relay equipment thatrequires a timing source to utilise the station clock, which itself may need to be installed.

For feeder replacement specific GPS aerial and receivers can be used with individual feederequipment. Separate GPS clocks are required when both main protections fitted on a feeder areunit protections.


17/26


Page 17 of 26

19. 110V DC & 48V DC SUPPLIES

19.1 Present Status

There is an agreed programme to replace most 110V dc batteries, chargers and distribution boardsby Maintenance Delivery - Electricity. There is a mix, some battery cells have recently beenreplaced whilst others are still quite old. Where new battery cells have been replaced thedistribution boards are still of an old design.

19.2 Objectives

During all activities involved in this contract the existing and final battery loads are to be assessed.Distribution boards can be extended where required but only after assessments of load andcapacity have been carried out and point to design acceptance.

Where necessary batteries should be replaced with new TS compliant units. The guidance withinOperational Engineering & Safety Bulletin (OESB) 14/2000, Issue 2, 01/02/2001 must be followed.This states that:

When the installation is a substation central/common battery where dedicated battery roomaccommodation exists to facilitate open rack mounting, Plant cells are to be used. Thisalso applies when existing systems deploying VRLA batteries are being replaced.

All new sites designed with common substation batteries must be specifically configured tosafely accommodate and ventilate Plant technology as stated.

Smaller capacity installations which are to be accommodated where space and ventilationis at a premium, for example in blockhouses, telecommunications rooms, LVAC rooms etcmay employ VRLA cells as an alternative to Plant cells.

Whenever batteries are replaced, the charger/distribution boards must be assessed toensure that they remain suitable for the specific characteristics and performance of thenew battery.

Where 48V batteries and chargers have been rendered partially or completely un-used by work onthis contract the contractor shall rationalise on the remaining units. The redundant units shall bedisposed of in an approved manner.

20. 415V LVAC SUPPLIES.

20.1 Objectives

LVAC board extensions or spare way equipping may be required as part of this contract,assessment of load and capacity must again be carried out beforehand.

21. SYNCHRONISING & VOLTAGE SELECTION

21.1 Present Status

In most installations a Brush Syscheck Relay is used for synchronising. A Syscheck relay isprovided for each synchronised breaker. A voltage selection scheme is used to switch the incomingand running volts to the selected Syscheck. A synchronising interface unit (a Microsol unit forMETRO installation or an SCS function for SCS equipment) is used to pass remote control signalsto the Syscheck to close the circuit breaker under the different synchronising closure modes.

21.2 Objectives

Where identified the equipment is to be replaced with TS 2.24 designed equipment. The newlyinstalled schemes should meet the requirements of TS 3.24.60.

When refurbishing protection on double busbar circuits the synchronising should be transferred intothe new bay solution for both manual synchronising and DAR.


18/26


Page 18 of 26

When a new control system only is being installed on a double busbar bay or on a mesh substationthe manual synchronising should reside within the bay controller and the existing system retainedfor use by the DAR relays.

21.3 Synchronizing Voltage Monitor ing

Incoming volts MCB auxiliary contacts should be used circuit by circuit to both inhibit all closecommands (both manual and automatic) on the specific circuit IED (but not the emergency close)and also raise a site alarm. No fuses or links should be left in any bay specific synchronisingscheme wiring and all MCB auxiliary contacts should operate the above-mentioned functions.

The alarm to be raised should be

1828 Site CTRL SYS ABNORMOn/Off 42208 SYNCH VT SUPLY Flty/Hlthy

Monitoring of running volts is achieved by applying the above to all VT supply sources.

For mesh sites the above shall apply but operation of the MCB on the line VT shall inhibit all closecommands (both manual and automatic) on the IEDs on all adjacent local circuit breakers. Theclose inhibition shall only apply when the line disconnector is closed.

Note that all close commands includes both synchronising and non-synchronising closecommands.


22. INFORMATION MANAGEMENT UNIT (IMU)

22.1 Present Status

Limited number of IMUs installed at present. Current method of collecting information is with theuse of standalone system that has dial-up access to specific devices such as SCS, fault recorders,metering, etc.

22.2 Objectives

If scope of work includes the SCS replacement then an IMU with TS 2.24 designed equipment

should be installed.

23. SUPERVISION

23.1 Present Status

Specific relays used to supervise individual relays and equipment. Separate schemes to provideVT, CT, DC Supply and Trip supervision facilities.

23.2 Objectives

Where identified, the equipment is to be replaced with TS 2.24 designed equipment. Thepreference for VT and CT supervision is that the supervision facility is integrated with theequipment that utilises the VT or CT input. The watchdog of the powered IED can undertake DC

supply supervision function.


23.3 CT Supervision

With respect to CT supervision the following requirements apply:-

For all relays with single three phase direct CT inputs (i.e. no resistors and auxiliary switchesand one three phase CT) then the CT supervision shall be disabled,


19/26


Page 19 of 26

For all relays with > one direct three phase CT input then the CT supervision shall be adifferential measurement and shall be enabled.

For all relays with > one direct CT input where the CT supervision is not a differentialmeasurement, but the protection setting is sensitive then the CT supervision shall bedisabled.

For all other cases the CT supervision facility shall be enabled.

23.4 Trip Circuit Supervision

With respect to trip circuit supervision the following requirements shall apply:-

Where a single IED is being used to monitor two trip circuits, NG require a further alarm tobe brought out from the watchdog. This should indicate that the trip circuit supervisionfunction is no longer available.

The following alarm shall be provided and shall be included in the GEM:-

Raw alarm :- "TRIP CCT SUPVN FLTY/HLTHY" Grouped as:- "SITE PROT ABNORMALON/OFF".

24. TESTING FACILITIES

24.1 Routine Trip Test Facilities

All Main Protection IEDs shall be fitted with a lockable trip test facility to simulate all requiredoutputs for a Main Protection trip test (including auto switching). Note that a Main Protection IED isone which carries out a Main Protection function such as transformer protection, mesh cornerprotection, and reactor protection.

The trip test shall be possible with the relay in TEST mode but not overriding any functionalityblocked by this mode(see below).

24.2 Test /Normal Facili ties

Each IED is required to be fitted with a Test/Normal switch to enable it to be isolated prior to workbeing carried out.

For feeder protections with integral intertripping, the test/normal switch shall disable all tripoutputsin that IED and there is no requirement for a separate DTT Out/In switch.

A channel test facility is not required on relays which monitor the integrity of the communicationschannel continuously and which provide signalling statistics automatically.

For all protections with remote relays the following basic Test/Normal functionality is required:-

1. With one relay in test, all trip outputs are physically blocked by the switch and all remotecommunication blocked with the exception of the relay in test signal to remote peers.

2. With all relays in test, 1. above applies but all remote communication should continue as normal.

3. With one relay in test, Feeder unit protection relays should prevent the remote relays(s) fromoutputting a differential trip.

4. With one relay in test, Feeder non-unit protection relays should allow the remote relays(s) tooperate normally including remaining in blocked mode.


20/26


Page 20 of 26

24.3 Test Points for On Load or Stage 2 Commissioning Checks

As the modern protection test blocks cause the CT circuits to be shorted out when a test plug isinserted it is difficult to use them for on load or stage 2 commissioning tests as the Voltage cannotbe monitored unless the CTs are shorted out. The test block & plug design should thereforeenable the CT circuits to be maintained when a plug is inserted to monitor the circuit volts.Alternatively provision should be made within the suppliers designs for suitable test points orterminal blocks where connections can easily be attached to monitor circuit volts for the purposesof on load and phasing out checks.

25. CONTROL SYSTEMS

25.1 Plant Interface Engineering for New or Modified Control Systems

The Contractor will determine the drawings required to carry out the works from the drawings /records held at each site.

Where the existing plant interface is found to be incomplete for control & data acquisition purposes,the required interface is to be designed & provided by the supplier. This may include the supply ofancillary equipment.

Where synchronising is required on Circuit Breakers, this shall be provided within the SubstationControl System functionality or by utilisation of an external scheme using Type Registeredequipment.

The suppliers proposed methodology for the transfer of the plant connections from the existing tothe new control system shall be agreed in advance with National Grid.

The design should recognise that there may be considerable delays between transferring circuitsand it will be necessary to operate the site with the control of circuits split between the existing andthe new control systems. The transition strategy shall be agreed in advance with National Grid andmust be managed to ensure there is no disruption to operational facilities.

In addition to the transfer of facilities to the new Substation Control System the contractorsengineering package will need to take account of the following:

That a certain number of defined facilities will need to be maintained on the old SubstationControl System for ENCC purposes until after the final data switch date. This will normallybe scheduled after the completion of the last circuit outage.

The recovery of any temporary wiring or redundant equipment after the final data switchdate

Where it is necessary to derive analogue signals from transducers, the Supplier shall provide orreplace the transducers (as necessary) to ensure the overall design life of fifteen years.

The supplier needs to be aware that an Emergency Return To Service (ERTS) Request may bemade by National Grid at any time whilst access to the Grid System is being permitted. TheContractors design at each site should take account of the ERTS times quoted for particularcircuits within any specific contract.

The supplier must design the works at each site to take account of any site-specific restrictions(particularly those related to safety matters, such as exclusion zones).

In order to cater for future expansion at each substation all works should result in the removal of asmuch equipment (i.e. wall boxes / cubicles / panels etc.) as possible. Suppliers are requested toengineer the works to achieve this objective, however it is recognised that this may result in theprovision of additional, new cabling direct to plant items.


21/26


Page 21 of 26

25.2 Synchronising Interface to TS 3.24.60

TS 3.24.60 specifies the synchronising requirements to be provided for new and Control Systemreplacement sites. It does not specify the complete Circuit Breaker Close control requirements nordoes it give guidance on the configuration requirements necessary to meet the needs of NationalGrids Control Centre computer, the IEMS. The following sections detail these issues.

25.2.1 Circuit Breaker Close Requirements.

Circuit Breaker close requirements fall into two categories:

1. Closure is never conditioned by a synchronising relay and simple OPEN/CLOSE controlsonly are required. These controls simply cause the energisation of IPO/IPC relays asappropriate and feedback signals are provided by the circuit breaker double point plantstates.

2. Circuit Breaker closure is normally conditioned by on-site synchronising functionalityClosure via the synch function is covered by TS 3.24.60. IEMS OPEN/CLOSE controlsappear the same as for the non-synch breaker above and feedback signals are providedby the circuit breaker double point plant states. In this case however the CLOSE control isconditioned by on-site equipment. No other feedback is required. Circuit breakers of thistype however require an additional Emergency Close control. This feature is not coveredby TS 3.24.60.

The Emergency Close control issued by the IEMS results in the energisation of the IPC relaycompletely by-passing the on site synch function. In this case however it is not possible to use thecircuit breaker double point plant state for IEMS feedback purposes. A pseudo bit generated bythe SCS should provide feedback for this Emergency Close control. This bit should normallyreturn a state of Emergency Close OUT (1) to the IEMS. When it is becomes necessary to sendan Emergency Close control the IEMS will drive the standing bit 1 to 0, and the SCS will output acontrol pulse to the appropriate circuit breaker IPC. The SCS should respond by setting thepseudo bit, temporarily to Emergency Close IN (0) (providing the confirmatory feedback to theIEMS). After a period of say 2 seconds the SCS should reset the pseudo bit to Emergency CloseOUT (1), in readiness for the sending of the next Emergency Close control from the IEMS. Whenthe circuit beaker closes the normal (CLOSED) double point plant state will sent to the IEMS.

The required grouping strategy for the TS 3.24.60 indications/alarms is as follows:

PER(At SCP)

INFORMATION VALUE (event list)On (1) / Off (0)

PER(At ENCC)

VALUE (GI74)On (1) / off (0)

CB SYNCH INPROGRESS

IN / OUT N/A Not Required

CB SYSTEM SYNCH INPROGRESS

IN / OUT CB IN/OUT

CB SYNCH FUNCTION FLTY/HLTHY SITE CNTRL SYS ABNORMALON/OFF

CB SYNCH VT FAIL ALARM/OFF SITE CNTRL SYS ABNORMALON/OFF

NB: ENCC SITE = One grouped alarm per voltage level

25.2.2 Emergency Close Requirements on Legacy SCSs.

In line within the new TS 3.24.60 for simplified synchronising there is now a requirement for anemergency close control command. As stated above a pseudo bit generated by the SCS shouldprovide feedback for this control.

However a number of National Grids current population of SCSs (i.e. pre NICAP) cannot providea software generated feedback indication for the above mentioned control.

To overcome this problem at these sites it is necessary for the bay solution provider to engineer amechanism for providing this feedback for the emergency control command.


22/26


Page 22 of 26

This solution should be engineered in regardless of the manufacturer of the existing SCS typepresent on site.

National Grid considers the following sketch in Appendix 1 to be a possible design solution.

25.3 Automatic Tap Change Control (ATCC)

In designing ATCC solutions, the following shall be considered: -

Provision of an ATCC system at a site requires that all necessary (SGT) circuits areconnected to the point of control of the ATCC functionality (plus information from LVbusbars).

National Grid requires suppliers to outline within the DID a detailed explanation of how thetransfer from any existing ATCC system at a site to the ATCC functionality with the newcontrol system will be accomplished without any degradation in the tapchanger facilities atthe site, with testing intentions for any temporary wiring installed and how removal of suchtemporary wiring will be achieved.

The Contractor will be required to design and implement graphical interfaces for use with theSubstation Control Point, based on the site Operation Diagrams. Sample graphical interfacedesigns must be submitted as part of the DID.

25.4 Interlocking

When carrying out SCS replacement work when the existing equipment contains softwareinterlocking a suitable strategy must be developed to transfer the interlocking from the old to thenew system. The methodology for transferring the interlocks must be fully outlined in the DID andagreed with National Grid prior to the commencement of any transfer.

Full site interlocking must be available throughout the period of transfer from the old to the newsystem.

26 CIRCUIT BREAKER REPLACEMENT

This section applies to both circuit breaker replacement and CB control schemereplacement.

26.1 400kV Circuit Breakers

Generally all existing 400kV circuit breakers are fitted with duplicate tripping systems. Thesefacilities must be maintained when the circuit breakers and/or the protection equipment arereplaced. Any new equipment must be fitted with these facilities.

Circuit breakers with 3 phase tripping facilities must be fitted where possible. This is to reducecomplexity within the tripping circuitry, as single-phase mechanisms require two independent tripcircuits per pole. This complexity is particularly bad at Mesh substations.

26.2 275kV Circuit Breakers

All new 275kV circuit breakers are specified with duplicate tripping facilities. However a largepercentage of older 275kV air blast & bulk oil circuit breakers are fitted with a single trip coil. Thisparticularly applies to those installed in the 1950s & 60s.

When replacing such a circuit breaker the new one shall have duplicate trip coils in compliance withTS 3.2.1. Where the existing system is fitted with a single tripping system the trip circuits must bere-engineered to form duplicate trip circuits in line with the TS 3.24 series of specifications. Thisapplies to all circuit types: i.e. feeders, transformers, bus sections, bus couplers, mesh circuitbreakers etc.


23/26


Page 23 of 26

When replacing the protection on a circuit fitted with a single trip coil circuit breaker the protectiontrip circuits must be fully duplicated. This includes providing functions such as trip circuitsupervision, simulated trip test facilities and isolation links for both trip circuits. However the tripcontacts should be arranged to operate the single coil with the circuit being readily convertible toduplicate tripping if the circuit breaker is replaced.

It is possible to convert some of the single trip coil circuit breakers to duplicate coils if so desired,but this work must be carefully considered. In particular type JW420 bulk oil circuit breakers arefitted with a second trip coil to allow the circuit breaker to be used for high speed auto reclose. Thisfacility is not used on National Grids system and is not suitable for use as a second trip coil withoutmechanical modification as the coil does not cause the circuit breaker to fully latch. If it isnecessary to use this coil as a second trip coil agreement must be obtained from the relevantNational Grid project engineer to carry out this work. The design and method of modifying the triplatch must also be agreed with National Grid prior to the work being commenced. Generally if aprotection refurbishment is carried out on a circuit fitted with a JW420 with a single trip circuit itshould be returned to service with the same trip circuit in service.

26.3 Simulated Trip Test Socket Facilities

A Simulated Trip Test Socket as described in TPS(standard) 12/57 is required for each trip circuit,i.e. for trip circuit 1 and trip circuit 2. This will normally take the form of a yellow STTS socket, butan alternative arrangement may be installed by agreement from National Grid. The facility should

provide the functionality to operate the trip circuit and provide an operation indication withouttripping the main circuit breaker.

27. AUTHORISATION/REVISION

Rev N Date Author Revision Details Authorised by

1 20/01/06 A J Chamberlain First Issue, previous documents& CDCs combined into DH.

Keith Harker

2 29/06/07 A J Chamberlain General Update to take accountof project experiences.Additions shown in red.

Keith Harker


24/26


Page 24 of 26

APPENDIX 1: EMERGENCY CLOSE REQUIREMENTS FOR LEGACY SCSS

EC

Aux

CB

Emergency

Close +

CB

Emergency

Close -

CB

Emergency

Close indication

Common

SCS I/O

UnitSCS I/O

Unit

IP C

SynchronisingIE D

Synchronising

IED

Sketch to be used for guidanceonly and does not represent a fully

engineered solution

CB Close + CB Close -

SCS + SCS -

SynchronisingIED


25/26


Page 25 of 26

APPENDIX 2: REMOVAL OF EXISTING POWER LINE CARRIER EQUIPMENT.

Series Tuningunit to beremoved

Coax removed from thisterminal may also have aspark gap to earth. (Also to beremoved).

Blankingplate tobe fitted

New tinned copper link to be fitted.Original size fitted was 1x 12.5 mm


26/26


Earth link to be fitted1x12.5 mm Tinnedcopper, after removalof coax/spark gap.

Existingearth bar.

Documents

National Grid Design Handbook dh01