EDS 08-2108 Supplies to HOT Sites and National Grid Siteslibrary.ukpowernetworks.co.uk/library/asset/ca706f47-660b-47c5-a1... · EDS 08-2108 SUPPLIES TO HOT SITES AND NATIONAL GRID

Document Number: EDS 08-2108

Version: 4.0

Date: 01/02/2018

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ENGINEERING DESIGN STANDARD

EDS 08-2108

SUPPLIES TO HOT SITES AND NATIONAL GRID SITES

Network(s): EPN, LPN, SPN

Summary: This standard details the requirements for the provision of LV supplies to higher voltage sites (e.g. 132kV, 33kV etc.) that are HOT or owned by National Grid.

Author: Stephen Tucker Date: 01/02/2018

Approver: Paul Williams Date: 05/03/2018

This document forms part of the Company’s Integrated Business System and its requirements are mandatory throughout UK Power Networks. Departure from these requirements may only be taken with the written approval of the Director of Asset Management. If you have any queries about this document please contact the author or owner of the current issue.

Applicable To

UK Power Networks External

☒ Asset Management ☒ G81 Website

☒ Capital Programme ☐ Contractors

☒ Connections ☐ ICPs/IDNOs

☒ Health & Safety ☐ Meter Operators

☒ Network Operations

☐ Procurement

☒ Technical Training

☐ UK Power Networks Services

Supplies to HOT Sites and National Grid Sites Document Number: EDS 08-2108

Version: 4.0

Date: 01/02/2018

© UK Power Networks 2018 All rights reserved 2 of 32

Revision Record

Version 4.0 Review Date 05/10/2022

Date 01/02/2018 Author Stephen Tucker

Reason for update: Introduction of HV cables with aluminium wire screens

What has changed:

Ring connection cable screen bonding for aluminium wire screens added (Section 7.3.2).

Label 3 revised and material codes added to Table 7-1 (Section 7.5)



Reason for update: Periodic review

What has changed:

Consideration of National Grid COLD sites included (Section 1).

Tee connection arrangement added (Figure 6-1 and Section 6.2.5.2).

HV cable screen bonding/insulation requirements clarified (Section 7.3).

References updated (Section 9).

National Grid COLD site registration form included EDS 08-2108C).

Document renumbered from EDS 08-0121 to EDS 08-2108



Reason for update: Document revised following business feedback.

What has changed:

Process added (Section 5).

Design options (Section 6.2) and installation requirements (Section 7) refined.

HV cable screen bonding photos added (Figure 7-2).

Warning label availability updated (Section 7.5).

Operational requirements including Power On updated (Section 8.2/8.3).

Recent examples added (Appendix A).

Example operational document added (Appendix B).

Document title amended.



Original


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Contents

1 Introduction ............................................................................................................. 5

2 Scope ....................................................................................................................... 5

3 Abbreviations and Definitions ................................................................................ 5

4 Background ............................................................................................................. 6

4.1 Hot Site ..................................................................................................................... 6

4.2 Earth Potential Rise (EPR) ........................................................................................ 6

4.3 Substation Earthing Database ................................................................................... 6

5 Process .................................................................................................................... 7

6 Design Requirements .............................................................................................. 8

6.1 Information Requirements ......................................................................................... 8

6.2 Supply Options .......................................................................................................... 8

7 Installation Requirements ..................................................................................... 18

7.1 Secondary Substation ............................................................................................. 18

7.2 Jointing .................................................................................................................... 18

7.3 HV Cables ............................................................................................................... 18

7.4 Miscellaneous Materials .......................................................................................... 20

7.5 Warning Labels ....................................................................................................... 21

8 Operational Requirements .................................................................................... 23

8.1 General ................................................................................................................... 23

8.2 Documentation ........................................................................................................ 23

8.3 Power On ................................................................................................................ 23

8.4 NetMap .................................................................................................................... 24

8.5 National Grid Site .................................................................................................... 25

9 References ............................................................................................................. 26

9.1 UK Power Networks Standards ............................................................................... 26

9.2 National Standards .................................................................................................. 26

10 Dependent Documents.......................................................................................... 26

Appendix A – Examples ................................................................................................... 27

Appendix B – Operational Document .............................................................................. 32

Appendix C – National Grid COLD Site Form .................................................................. 32


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Figures

Figure 5-1 – Process Flowchart ............................................................................................ 7

Figure 6-1 – Supply Options Overview .................................................................................. 9

Figure 7-1 – RMU Cable Screen Bonding ........................................................................... 19

Figure 7-2 – RMU Cable Copper Wire Screen Bonding ...................................................... 19

Figure 7-3 – Ring Connection Cable Screen Bonding – Aluminium Wire Screen ................ 20

Figure 7-4 – Ring Connection Screen Cable Bonding – Copper Wire Screen ..................... 20

Figure 8-1 – Power On HOT Site Annotation ...................................................................... 24

Figure A-1 – LV Supply to National Grid 22kV Substation at Acton Lane ............................ 27

Figure A-2 – LV Supply to National Grid 22kV Substation at Acton Lane ............................ 27

Figure A-3 – Rayleigh 400kV and 132kV Substations ......................................................... 28

Figure A-4 – Rayleigh 400kV and 132kV Substations – Power On Extract .......................... 28

Figure A-5 – Norwich Main 400kV and 132kV Substations ................................................. 30

Figure A-6 – LV Supply to Norwich Main 400kV and 132kV Substations ............................ 30

Figure A-7 – LV Supply to Bramford 400kV and 132kV Substations ................................... 31

Tables

Table 4-1 – EPR Threshold for a HOT Site Classification ..................................................... 6

Table 6-1 – Supply Options Overview ................................................................................... 8

Table 7-1 – Warning Labels ................................................................................................ 21

Table 8-1 – Power On HOT Site Pin Text ............................................................................ 23

Table 8-2 – NetMap HOT Site Label ................................................................................... 24

Table 8-3 – NetMap National Grid Label ............................................................................. 25


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1 Introduction

This standard details the requirements for the provision of LV supplies to all higher voltage sites (e.g. 132kV, 33kV etc.) that are either HOT or owned by National Grid. Supplies to these sites require special consideration to avoid the earth potential rise (EPR) during an earth fault being exported onto the HV or LV network and into a customer's premises where it could cause danger to life or damage to property.

Note: Not all National Grid sites are classified as HOT but they should be treated as HOT for the purpose of

providing LV supplies as detailed in this standard. However where National Grid can demonstrate that a site will remain COLD for its entire lifetime a standard HV or LV supply from a dedicated substation may be provided in accordance with the relevant design standard. This non-standard practice requires explicit written agreement between UK Power Networks Asset Management Earthing Engineer and National Grid Earthing Specialist Policy Development Engineer and shall be recorded using form EDS 08-2108C (Appendix C). NetMap shall be annotated as shown in Section 8.5.

2 Scope

This standard applies to the provision of LV supplies in EPN, LPN and SPN to:

UK Power Networks grid and primary substations classified as HOT sites.

Third party HOT sites.

All National Grid sites.

This standard does not apply to:

Supplies to HOT secondary substations; refer to EDS 06-0014 and ECS 06-0023.

Supplies to mobile telephone base stations on towers; refer to EDS 08-2109.

This standard applies to designers, planners and field staff working on LV connections.

3 Abbreviations and Definitions

Term Definition

COLD Site A site where the EPR is less than 430V or 650V (for high reliability protection)

EPR Earth potential rise – the potential (voltage) rise that occurs on any metalwork due to the current that flows through the ground when an earth fault occurs on the network

High reliability protection

Main protection systems that clear the fault current within 200ms

HOT Site A site where the EPR is greater than 430V or 650V (for high reliability protection)

NetMap UK Power Networks graphical information system (GIS)

Normal reliability protection

Main protection systems that clear the fault current in excess of 200ms

Power On UK Power Networks network management system

ROEP Rise of earth potential – another term for EPR


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4 Background

4.1 Hot Site

A site is classified as HOT when the earth potential rise (EPR) during an earth fault exceeds 430V or 650V as defined in Table 4-1.

Table 4-1 – EPR Threshold for a HOT Site Classification

Substation Voltage Source Circuit Protection

EPR Comments

400kV, 275kV, 132kV, 66kV, 33kV, 25kV

High reliability 650V Main protection systems that clear the earth fault current within 200ms

Normal reliability 430V Main protection systems that clear the earth fault current in excess of 200ms

20kV, 11kV, 6.6kV Normal reliability 430V Main protection systems that clear the earth fault current in excess of 200ms

4.2 Earth Potential Rise (EPR)

When an earth fault occurs on a cable or at a substation a proportion of the fault current will return to the source substation through the ground. This ‘ground return’ current will flow into the ground through the earth connection(s) closest to the fault; the current flow through the substation earth resistance will cause the voltage of the substation earth connections to rise above that of a remote (or true) earth. This voltage is known as the earth potential rise or EPR.

Note: Some current will flow through the cable screen back to the source and some will flow through the ground,

it is only the current that flows through the ground that causes the EPR.

4.3 Substation Earthing Database

The substation earthing database1 contains the available earthing related data for all grid and primary substations together with a substation classification of HOT or COLD. For further information refer to EDS 06-0002. If a HOT zone plot for an existing UK Power Networks HOT substation is required please contact the document author.

Any relevant information to the connection can be provided by the UK Power Networks Connection Designer if appropriate.

1 UK Power Networks Substation Earthing Database is available from the UK Power Networks Intranet using the following link Substation Earthing Database.

http://powernet/intranet/asset-management/engineering-standards/earthing/


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5 Process

An overview of the design and implementation process is shown in Figure 5-1. The sections that follow provide further details on each part.

Obtain site information (EPR,

HOT zone etc)

(Section 5.2)

Design secondary substation

using earthing design tool

(EDS 06-0014)

HV

START

Ensure earthing doesn’t

extend outside the HOT zone

END

HV or LV supply?

Customer to provide isolation

transformer*, RCD and earth

(Table 6-1)

LV

Construct substation in

accordance with ECS 06-0023

(Section 7.1)

Isolate HV cable sheaths,

install cables in ducts etc

(Section 7.3)

Apply warning labels

(Section 7.5)

Prepare operational document

(Section 8.2)

Select supply option

(Table 6-1)

Load operational document

into Alfresco

(Section 8.2)

Update NetMap

(Section 8.4)

Prepare SAN showing

HOT Site pins

(Section 8.3)

Apply pins to Power On

(Section 8.3)

Design Delivery Network Records

Apply warning labels

(Section 7.4)

Provide supply from LV

network without an earth

terminal (TT earthing)

Connect substation to main

earthing system of higher

voltage substation

Design supply with TT earth in

accordance with

EDS 08-2100 or EDS 08-2101

(Section 6.2.3)

Review operational document

with Network Manager and

Operational Safety Manager

(Section 8.2)

Link Power On to operational

document in Alfresco

(Section 8.3)

*The isolation transformer is

required to isolate the HOT

site from the UK Power

Networks distribution network

and prevent the EPR being

transferred to other customers.

*The isolation transformer is

required to isolate the HOT

site from the UK Power

Networks distribution network

and prevent the EPR being

transferred to other customers.

Figure 5-1 – Process Flowchart


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6 Design Requirements

6.1 Information Requirements

The following information, which should be requested from the customer, is required to enable a suitable supply to be designed:

Maximum earth potential rise.

Latest plot of the HOT zone and necessary potential contours.

Other earthing information i.e. soil resistivity, earthing study results, position of buried services/metalwork etc.

6.2 Supply Options

6.2.1 Overview

An overview of various supply options are detailed in Table 6-1 and shown in Figure 6-1. The specific requirements for each option are detailed in the sections that follow.

Table 6-1 – Supply Options Overview

Option Source Description Section

1 Secondary Substation

HOT grid/primary site supply from a dedicated secondary substation inside the HOT zone

6.2.2

2 Dedicated secondary substation outside the HOT zone 6.2.3

3 RMU Outside the HOT Zone and a Transformer Inside the HOT Zone

6.2.4

4 Dedicated secondary substation inside the HOT zone 6.2.5

5 Overhead Line

Dedicated transformer/substation inside HOT Zone 6.2.6

6 Dedicated transformer/substation outside HOT zone 6.2.7

7 LV Network Via isolation transformer 6.2.8


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LV EarthHV Earth

HOT Grid/Primary Substation

HOT Site

Supplies Only

Normal

Supplies

HV/LV Earth

HV Earth

HOT Site

Metalwork/

LV Earth

HOT Site

HOT Site

Supplies Only

LV EarthHV Earth

HV Overhead

Network

HOT Site

HOT Site

Supplies Only

LV EarthHV Earth

HV Overhead

Network

HOT Site

HOT Site

Supplies Only

HV/LV

Earth

HV Overhead Network

Option 7: LV Network using an Isolation Transformer

HOT Site

LV Earth

LV Network

Isolation TxPole Tx

Pole Tx

HOT Site

Supplies Only

HOT Site

Supplies Only

RMU

RMU

RMU

RMU

HV

Network

HV/LV Earth

HV

Network

Normal

Supplies

Normal

Supplies

HOT Site

HOT Site

Supplies Only

HV/LV

Earth

RMU

RMU

RMU

HV Network

HV Network

HV Network

HV Network

LV Network

HV

NetworkHV/LV

Earth

Option 5: Overhead Line – Dedicated Transformer/

Substation inside HOT Zone

Option 6: Overhead Line – Dedicated Transformer/

Substation Outside HOT Zone

Option 1: HOT Grid/Primary Dedicated Secondary

Substation Inside the HOT Zone

Option 4: Dedicated Secondary Substation Inside the

HOT Zone (ring or tee connection)

Option 2: Dedicated Secondary Substation Outside the

HOT Zone

Option 3: RMU Outside the HOT Zone and a Transformer

Inside the HOT Zone

HV Overhead Network

HV/LV Earth

HOT Site

HOT Site

Supplies Only

RMU

Figure 6-1 – Supply Options Overview


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6.2.2 Option 1: HOT Grid/Primary Site Supply from a Dedicated Secondary Substation Inside the HOT Zone

Requirement Details

Supply Source HV Cable

Arrangement

LV EarthHV Earth

8m

HOT Grid/Primary Substation

HOT Site

Supplies Only

Normal

Supplies

HV

Network

HV/LV Earth

Notes:

1 - EPR <2kV

2 - Warning labels

1

1 2

4 2

7

RMU

RMU

28

Application/EPR Limit Any HOT grid or primary substation supplying 11/6.6kV distribution network

Type of Supply Dedicated standard secondary substation located within and supplied from the HOT grid/primary substation

Substation Earthing Standard earthing arrangement designed in accordance with EDS 06-0014 using the earthing design tool

Where the secondary substation is installed within the earthing system of a higher voltage substation (e.g. grid, primary or National Grid substation) it should be connected to the main earthing system via two separate connections and additional earth rods are not required.

Supply Earthing Combined HV/LV earth bonded to main substation earth

Other Requirements Substation generally first leg out of grid/primary switchboard or via spare circuit-breaker.

HV/LV earths segregated at the next downstream substation unless the transfer voltage is below the 430V

Label (from Table 7-1) Label 4 at substation. Labels 1, 2, 7 and 8 at next substation

Comments EPR limit set by transformer LV winding power frequency withstand voltage at the downstream substation


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6.2.3 Option 2: Dedicated Secondary Substation Outside the HOT Zone

Requirement Details


Arrangement

HV

Network

HV

Network

HOT Site

HOT Site

Supplies Only

LV EarthHV Earth

32

Notes:

1 - EPR <2kV

2 – Neutral-earth link removed

3 - LV cable installed in insulated duct

4 - Warning labels

1

4

7

4

4

4

8m

4

RMU

2

1

8

Application/EPR Limit Any HOT site where the EPR is less than 2kV

Type of Supply Dedicated standard secondary substation located outside the HOT zone



Supply Earthing Segregated HV/LV earth.

HV earth installed outside the HOT zone and LV earth bonded to HOT site earth

Other Requirements LV cable in insulated duct to preserve insulation integrity.

Neutral-earth link removed and protected by insulated cover

Label (from Table 7-1) Labels 1, 2, 4, 7 and 8 at substation. Label 4 at HOT site

Comments Equivalent to NG TS 3.1.2 Figure 3.

EPR limit set by LV cable sheath power frequency withstand voltage


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6.2.4 Option 3: RMU Outside the HOT Zone and a Transformer Inside the HOT Zone

Requirement Details


Arrangement

HV

Network

HV Earth

HV

Network

HOT Site

Metalwork/

LV Earth

Notes:

1 - EPR <12kV

2 - HV cable sheath insulated at transformer

3 - HV cable installed in insulated duct

4 - Cable length less than 1km

5 - Warning labels

2

3 4

17

HOT Site

Supplies Only

5

5 5

4

6

RMU


Type of Supply Dedicated secondary substation with the RMU outside the HOT zone and the transformer inside the HOT zone

Note: A variation on this arrangement is to use a metering unit located with the RMU or with the transformer to provide an HV supply



Supply Earthing Segregated HV/LV earth

HV RMU earth installed outside the HOT zone. Transformer and LV earth bonded to HOT site earth

Other Requirements HV cable maximum length of 1km

HV cable screen bonded to RMU earth and insulated from the transformer (screen cut back inside cable box and insulated in accordance with 11kV Jointing Manual)

Label (from Table 7-1) Label 7 at substation. Labels 4, 5 and 6 at HOT site

Comments Equivalent to NG TS 3.1.2 Figure 2.

EPR limit set by HV cable sheath power frequency withstand voltage

Cable length to limit induced voltage to 65V due to single-point cable bonding.

Transformer faults should be cleared by the earth fault protection on the ring main unit


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6.2.5 Option 4: Dedicated Secondary Substation Inside the HOT Zone

6.2.5.1 Option 4a: Dedicated Secondary Substation Inside the HOT Zone – Ring Connection

Requirement Details


Arrangement

HV

Network

HV/LV Earth

HV

Network

HV/LV

Earth

Normal

Supplies

Normal

Supplies

HOT Site

Notes:

1 - EPR <5kV

2 - HV cable sheaths bonded

together and insulated from RMU

3 - HV cable installed in insulated

duct in HOT zone

4 - Warning labels

5

4

4

HOT Site

Supplies Only2

7 4

7 4

HV/LV

Earth

See Figure 8

RMU

RMU

RMU

3

3


Type of Supply Dedicated standard secondary substation located in the HOT zone



Supply Earthing Combined HV/LV earth bonded to main site earth

Other Requirements HV cable screens connected together using suitable size bond and insulated at RMU from site earth

HV cable in insulated duct in HOT zone to preserve insulation integrity

Label (from Table 7-1) Label 7 at upstream and downstream substations either side of HOT site. Labels 4 and 5 at HOT site

Comments EPR limit set by the termination method of the bonding between the cable screens.

Note: The power frequency withstand voltage of the HV cable screen is 12kV and the insulated stud is 7kV


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6.2.5.2 Option 4b: Dedicated Secondary Substation Inside the HOT Zone – Tee Connection

Requirement Details


Arrangement

HV

Network

HV/LV Earth

HV

Network

HV/LV

Earth

Normal

Supplies

Normal

Supplies

HOT Site

Notes:

1 - EPR <5kV

2 - HV cable sheaths bonded

together and insulated from RMU

3 - HV cable installed in insulated

duct in HOT zone

4 - Warning labels

5

4

4

HOT Site

Supplies Only

2

7 4

7 4

HV/LV

Earth

RMU

RMU

RMU

3

3


Type of Supply Dedicated standard secondary substation located in the HOT zone




Other Requirements HV cable screen insulated at RMU from site earth

HV cable in insulated duct in HOT zone to preserve insulation integrity

Label (from Table 7-1) Label 7 at upstream and downstream substations either side of HOT site. Labels 4 and 5 at HOT site

Comments EPR limit set by the termination method of the bonding between the cable screens.

Note: The power frequency withstand voltage of the HV cable screen is 12kV and the insulated stud is 7kV


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6.2.6 Option 5: Overhead Line – Dedicated Transformer/Substation Inside HOT Zone

Requirement Details

Supply Source HV Overhead Line

Arrangement

HOT Site

HOT Site

Supplies Only

HV/LV

Earth

HV Overhead

Network

HV Overhead

Network

Pole Tx

Notes:

1 - EPR <12kV

2 - Warning labels

2

1

4

7 2


Type of Supply Dedicated pole-mounted transformer or ground-mounted substation located inside the HOT zone


Other Requirements n/a

Label (from Table 7-1) Label 7 at pole. Label 4 at HOT site

Comments EPR limit set by transformer LV winding and LV cable sheath power frequency withstand voltage


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6.2.7 Option 6: Overhead Line – Dedicated Transformer/Substation Outside HOT Zone

Requirement Details

Supply Source HV Overhead Line

Arrangement

HV Overhead

Network

HOT Site

HOT Site

Supplies Only

LV EarthHV Earth

HV Overhead

Network

Pole Tx

3

1

2

Notes:

1 - EPR <12kV

2 - Cable installed in insulated duct

3 - Warning labels

8m

4

7 3


Type of Supply Dedicated pole-mounted transformer or ground-mounted substation located outside the HOT zone

Supply Earthing Segregated HV/LV earth.

HV earth installed outside the HOT zone and LV earth bonded to HOT site earth

Other Requirements n/a

Label (from Table 7-1) Label 7 at pole. Label 4 at HOT site

Comments EPR limit set by transformer LV winding and LV cable sheath power frequency withstand voltage


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6.2.8 Option 7: LV Network using an Isolation Transformer

Requirement Details

Supply Source LV Network

Arrangement

HOT Site

LV Earth

LV

Network

LV

Network

Isolation TxHOT Site

Supplies Only

1 Notes:

1 - EPR <12kV

2 - Cable installed

in insulated duct

3 - Warning labels

3

2

4

3

Isolation Transformer

Site Earth

RCD

Isolation TransformerRCD

LV Network

Site Earth

Cutout

Cutout

HOT Site

HOT Site

3 43

3 43


Type of Supply EDS 08-2101 or EDS 08-2100 supply from the LV network via 1:1 Δ-Υ isolation transformer (complying with BS EN 61558-2-4) in the HOT zone

Supply Earthing LV earth bonded to HOT site earth.

Isolation transformer enclosure bonded to site earth

Other Requirements Incoming neutral not connected to isolation transformer enclosure or metalwork. No earth terminal provided (TT earthing)

Isolation transformer protected by RCD

Label (from Table 7-1) Label 3 next to cut-out. Label 4 next to isolation transformer

Comments EPR limit set by LV cable sheath power frequency withstand voltage

For a customer site the boundary shall be at the cut-out and the provision, ownership and maintenance of the isolation transformer , RCD and LV earth is the customers responsibility


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7 Installation Requirements

7.1 Secondary Substation

The secondary substation earthing system shall be constructed in accordance with ECS 06-0023 paying particular attention to the additional HOT site requirements below:

Installation of HV cable screen bonding or insulation where required in accordance with Section 7.3.2 or Section 7.3.1.

Installation of separate HV and LV earths if required and

Removal of the neutral-earth link.

Removal/disconnection of associated 13A sockets.

Installation of isolation transformer for RTU supply.

Installation of appropriate warning labels (refer to Section 7.5) at both the HOT site and any other associated substations.

If installed within the earthing system of a higher voltage substation (e.g. grid, primary or National Grid) connected to the main earthing system via two separate connections.

7.2 Jointing

Jointing of cables between sites with high EPRs shall be carried out using insulated working practices in accordance with new procedure HSS 40 050 or, in the interim, National Grid instruction NSI 5.

Joints within the HOT zone shall be avoided. 11kV cable is available in 250m drums as standard or 1000m drums by special order.

7.3 HV Cables

7.3.1 Cable Screen – Tee Connection

If the secondary substation is located in the HOT zone and supplied via a tee connection the HV cable screen shall be insulated from the substation earth as follows:

For cables with aluminium wire screen (AWS) do not connect the length of tinned copper braid.

For cables with a copper wire (CWS) terminate the screen in in accordance with the 11kV jointing manual and then cut back, leaving a short tail.

Fully insulate the screen with heat shrink tubing and a heat shrink cap.

Ensure the insulated screen is positioned clear of all earthed metalwork.


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7.3.2 Cable Screen – Ring Connection

If the secondary substation is located in the HOT zone and supplied via a ring connection the HV cable screens shall be bonded together and insulated from the substation earth as shown in Figure 7-1 and Figure 7-2.

SW2 (RH) Cable Box

RMU

SW1 (LH) Cable Box

Aluminium or Copper Insulated Cable Sheath

Bond Sized to match Earthing System

Insulated Earth

Stud Removed

and Blanked Off

Heat Shrink

Boot

Connector

03196H or

MF15/5/SH

from 02806D

Cable Sheaths Insulated

from Cable Boxes

Cover

Connector with

Heat Shrink

Figure 7-1 – RMU Cable Screen Bonding

Figure 7-2 – RMU Cable Copper Wire Screen Bonding

For cables with an aluminium wire screen (AWS) terminate the screens using lug 02236J and the earth cable using connector 02236J. Bolt the two lugs together (Figure 7-3). Alternatively connector 04523C may be used.

For cables with a copper wire screen (CWS) terminate the screens and earth cable using connector 03196H (Figure 7-4).

Fully insulate the screen with heat shrink tubing and a heat shrink cap.

Ensure the insulated screen is positioned clear of all earthed metalwork.


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Figure 7-3 – Ring Connection Cable Screen Bonding – Aluminium Wire Screen

Figure 7-4 – Ring Connection Screen Cable Bonding – Copper Wire Screen

7.3.3 Lead Sheathed Cables

If lead sheathed (PILC) cables are connected to the HOT site they will export the EPR and therefore they shall be replaced with insulated sheathed cables within the HOT zone and five metres outside it.

7.4 Miscellaneous Materials

Application Material Code or Reference

Description Comments

11kV Cable Duct EAS 00-0002 Ducts and duct accessories Use 33kV ducts from Emtelle

LV Duct EAS 00-0002 Ducts and duct accessories

Cable Screen Bonding (AWS)

02356J Lug Aluminium Cable 300mm M16

02236J Mechanical Lug 70 to 120mm (10/12mm Hole)

04523C LV Plant Termination Kit S/C Cables

Cable Screen Bonding (CWS)

03196H Connector Straight Thru Main 300


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7.5 Warning Labels

The warning labels detailed Table 7-1 shall be installed as specified in Section 6.2. as most labels are of the adhesive type where they are to be used on a pole they should be affixed to suitable backing plate that can be fixed to the pole.

Table 7-1 – Warning Labels

No Situation/Location Reference2 (Material Code3)

Specification Label

1 Install in prominent position inside fence/enclosure

EDS 07-0009.117

(21515D)

100mm x 150mm adhesive label

2 In LV cabinet or micro/compact

EDS 07-0009.118

(21655V)


3 Next to the cut-out EDS 07-0009.121

(21657Q)


Next to the cut-out EDS 07-0009.178

(21691R)


4 Next to the cut-out and pole transformer

EDS 07-0009.131

(21649B)

100mm x 37.5mm adhesive label

5 Next to affected equipment

EDS 07-0009.132

(21650W)

100mm x 37.5mm adhesive label

6 On substation door EDS 07-0009.133

(21651G)


2 For the availability of labels without a material code please contact the author or refer to EAS 07-0021. 3 UK Power Networks logistics material code.


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No Situation/Location Reference2 (Material Code3)

Specification Label

7 On substation door EDS 07-0009.134

(21652R)


8 In LV cabinet or micro/compact

EDS 07-0009.171

(21517X)



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8 Operational Requirements

8.1 General

Any installation that involves different earthing systems which are not bonded together carries a level of risk should simultaneous contact occur between the two systems. Special care is needed when working on circuits or switchgear where access to the different earthing systems may be made possible. The main issues are:

Applying a circuit main earth at the HOT site or adjacent sites.

Working on cables between different earthing systems.

Insulated working should be considered where applicable, refer to HSS 40 050 for further information.

It is therefore important that the switchgear maintenance and cable working requirements are considered at the design stage.

8.2 Documentation

It is the joint responsibility of the senior authorised person, with the assistance of the designer and/or project manager, to determine any special operating arrangements and prepare an operational requirements document. An example document is included in Appendix B. The document shall be added to Alfresco and linked to the Power On HOT Site pin detailed in Section 8.3.

Any special operating arrangements should be approved by the Operational Safety Manager and the Control/Network Manager.

8.3 Power On

A HOT site pin shall be applied on the Power On diagram at each affected site to highlight any non-standard earthing requirements. The HOT site dressing pins shall be applied as below:

At the HOT site – on the circuit-breaker of all ring main units on site.

At sites either side of HOT site – on the substation circuit-breaker or ring main unit switch

An example is shown in Figure 8-1 both ‘Action Ln Opp Waxlow Rd National Grid’ (the HOT site with non-standard earthing) and the sites either side have HOT Site pins. Examples of the HOT Site pin text are shown in Table 8-1.

Table 8-1 – Power On HOT Site Pin Text

HOT Site

This substation provides a supply to a HOT site and has a non-standard earthing arrangement and/or insulated cable screens.

Refer to the attached site specific operating instructions for further information.

This substation shall not be used to provide LV supplies to other customers.

Warning Connected to a HOT Site

This substation is connected to a HOT site with a non-standard earthing arrangement and/or insulated cable screens.

Refer to the attached site specific operating instructions for further information.


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The relevant information should be included on the System Alteration Notice (SAN) to allow the diagram to be correctly annotated.

Figure 8-1 – Power On HOT Site Annotation

8.4 NetMap

On completion of the installation NetMap shall be updated to show:

That the substation cannot be used to provide LV supplies to other customers as shown in Table 8-2.

Insulated cable screens.

Sections of overhead line that should not be undergrounded.

Any other bespoke installation details.

Table 8-2 – NetMap HOT Site Label

HOT Site Supply

This substation shall not be used to provide LV supplies to other customers


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8.5 National Grid Site

Generally all National Grid sites are treated as HOT and shall be annotated on PowerOn and NetMap as detailed in Section 8.3 and 8.4. However where it has been agreed between UK Power Networks and National Grid that the site is to be classified as COLD NetMap shall be annotated as shown in Table 8-3.

Table 8-3 – NetMap National Grid Label

National Grid Dedicated Site Supply

This substation shall not be used to provide LV supplies to other customers


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9 References

9.1 UK Power Networks Standards

EAS 02-0000 Approved Equipment List - Cables and Joints

ECS 02-0011 11kV Jointing Manual

EDS 06-0002 HOT Site Management (internal document only)

EDS 06-0014 Secondary Substation Earthing Design

EDS 06-0017 Customer Installation Earthing Design

ECS 06-0023 Secondary Distribution Network Earthing Construction

EAS 07-0021 Signs and Labels for Operational Sites

EDS 08-2100 LV Customer Supplies

EDS 08-2101 LV Customer Supplies up to 100A Single-phase

EDS 08-2109 LV supplies to Mobile Phone Base Stations Mounted on 132, 275 and 400kV Towers (internal document only)

HSS 40 050 Controlling Impressed Voltages on Underground Cable Systems (future HSS document)

9.2 National Standards

National Grid TS 3.1.2 Earthing

National Grid NSI 5 Insulated Working on Cable Systems

10 Dependent Documents

EDS 06-0002 HOT Site Management (internal document only)

EDS 06-0017 Customer Installation Earthing Design

EDS 06-0019 Customer EHV and HV Connections (including Generation) Earthing Design and Construction Guidelines

ECS 06-0022 Grid and Primary Earthing Construction

EAS 07-0021 Signs and Labels for Operational Sites

EDS 07-1119 Substation Electrical Services

EDS 08-0149 Customer Supply Interface

EDS 08-1112 LVAC Supplies

EDS 08-2100 LV Customer Supplies


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Appendix A – Examples

A.1 National Grid Acton Lane 22kV

Acton Lane consists of 22kV National Grid substation as shown in Figure A-1. Although Acton Lane is not currently classified as a HOT site all supplies to National Grid sites have to be treated as HOT to cater for future changes to the network or an increase in fault level. An LV supply was requested by National Grid and provided from a secondary substation using option 4 (Section 6.2.5) as shown in Figure A-2.

Figure A-1 – LV Supply to National Grid 22kV Substation at Acton Lane

24843

Acton Ln Opp Waxlow Rd

National Grid

24650

Acton Lne Hamm

Med Res

24731

Waxlow Rd Unit A

Centrus

240

Gibbons Road

SW1

Panel 48

HOT

Site

Figure A-2 – LV Supply to National Grid 22kV Substation at Acton Lane


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A.2 Rayleigh Main

Rayleigh Main consists of a 400kV National Grid substation and a UK Power Networks 132kV substation. Rayleigh Main is HOT with a maximum EPR of 1777V for a fault on the 400kV network. The substations are shown in Figure A-3 and the supply arrangement is shown in Figure A-4.

Figure A-3 – Rayleigh 400kV and 132kV Substations

Figure A-4 – Rayleigh 400kV and 132kV Substations – Power On Extract

Rayleigh Main 132kV

Rayleigh Main 400kV

NG Switching Station 11kV

Rayleigh GIS Local and Local 2 11kV

CEGB 400 Grid11kV


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A.2.1 Rayleigh Main 400kV via NG Switching Station

NG Switching Station is a new secondary substation containing a ring main unit without a transformer. During the design and construction of this substation the switchgear at the CEGB substation located within Rayleigh Main 400kV was solidly bonded to the Rayleigh Main 400kV earth grid.

The 11kV cable that feeds into the CEGB substation was of PILC construction and the cable sheath was therefore not insulated from the soil. To separate the earthing the PILC cable was overlaid with plastic sheathed cable. The cable screen was insulated from the site earth in the CEGB substation. This is an example of Option 3 (Section 6.2.4).

A.2.2 Rayleigh Main 132kV Supply via Rayleigh GIS Local and Rayleigh GIS Local 2

Rayleigh Main 132kV has two disparate 400V three-phase supplies. Each is supplied from a separate secondary substation located 3m outside the Rayleigh Main 132kV substation fence. The secondary substations each have an independent earthing system but they are bonded together; however neither is bonded to the Rayleigh Main 132kV earth grid. The three-phase 400V supply from each of the secondary substations is bonded to the Rayleigh Main 132kV substation earth grid at the LVAC distribution board. At each secondary substation the LV neutral has been disconnected from the substation earth. This is where the rise of potential will occur during fault conditions. A label has been applied to draw attention to the arrangement. The power socket in the distribution substation has also been disconnected.

This arrangement prevents the earth potential rise occurring during a 400kV fault at Rayleigh Main 400kV from being exported onto the 11kV earthing system. It also prevents other customers from being supplied from this substation as any 400V connections would be bonded to HOT substation earth grid. This is an example of Option 2 (Section 6.2.3).


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A.3 Norwich Main

Norwich Main consists of a 400kV National Grid substation and a UK Power Networks 132kV substation as shown in Figure A-5. Norwich Main is HOT with a maximum EPR of 2650V for a fault on the 400kV network. A dual LV supply was requested by National Grid for the 400kV substation and a single LV supply was required for the 132kV substation.

The supplies were provided using option 4 (Section 6.2.5) from overhead line on one side and cable on the other as shown in Figure A-6.

Figure A-5 – Norwich Main 400kV and 132kV Substations

Norwich Main

400kV

Norwich Main

132kV

Norwich Main

132kV Local B

Pole 8 Pole 7

HV/LV Earth

HOT Site

Supply

Orange Mast

Ipswich Road

Normal

Supply

Pole 11APole 12 Pole 11

CableOHL

Norwich – London Liverpool St Main Line

HOT Zone

HV/LV Earth

Norwich Main

Dunston

HV/LV Earth

HOT Site

Supply 2

HOT Site

Supply 1

HV Earth

HV Earth

Figure A-6 – LV Supply to Norwich Main 400kV and 132kV Substations

Norwich Main 400kV

Norwich Main 132kV


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A.4 Bramford Grid

Bramford Grid consists of 400kV and 132kV substations. Bramford Grid is HOT with a maximum EPR of 2880 for a fault on the 400kV network. A ring supply was requested by National Grid for each substation. The supplies were provided using options 5 and 6 (Sections 6.2.6/6.2.7) from overhead line as shown in Figure A-7.

Pole 8b

Pole 7b

New

ABSD

HOT Zone

HV/LV

Earth

New

Secondary

Substation

Pole 9b

Euromast

Pole Tx

Pole 7c

Pole 1c

CEGB 400kV Site

CEGB 132kV Site

Bramford Grid

Temp SupplyHV/LV Earth

HV/LV

Earth

Pot

End

HV cable

in duct

Cable sheath

insulated

from earth

Cable sheaths

bonded to

steelwork earth

Bramford Grid

400/132kV

To be removed

when NG

construction

complete

To be removed at

later stage

Cable sheaths to

be connected to

steelwork earth

Figure A-7 – LV Supply to Bramford 400kV and 132kV Substations


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Appendix B – Operational Document

An example operational document for the Acton Lane example in Appendix A is available as a separate document EDS 08-2108B.

Appendix C – National Grid COLD Site Form

Form EDS 08-2108C register the classification of a National Grid substation as a COLD site for the purpose of providing an LV supply.