Download EDS 08-0121 Supplies to HOT Sites and

Document Number: EDS 08-0121
Date: 02/07/2015
ENGINEERING DESIGN STANDARD
EDS 08-0121
SUPPLIES TO HOT SITES AND NATIONAL GRID SITES
Network(s):
EPN, LPN, SPN
Summary:
This standard details the additional requirements for the provision of LV supplies to
higher voltage sites (e.g. 132kV, 33kV etc.) that are HOT or owned by National
Grid.
Owner:
Allan Boardman
Date:
02/07/2015
Approved By:
Steve Mockford
Approved Date:
24/07/2015
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 version.
Circulation
UK Power Networks
External
All UK Power Networks
G81 Website
Asset Management
Contractors
Capital Programme
ICPs/IDNOs
Connections
Meter Operators
HSS&TT
Network Operations
UK Power Networks Services
Other
THIS IS AN UNCONTROLLED DOCUMENT, THE READER MUST CONFIRM ITS VALIDITY BEFORE USE
Version: 2.0
Supplies to HOT Sites and National Grid Sites
Document Number: EDS 08-0121
Version: 2.0
Date: 02/07/2015
Revision Record
Version
2.0
Review Date
04/09/2017
Date
02/07/2015
Author
Stephen Tucker
Why has the document been updated: 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 sheath 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.
Version
1.0
Review Date
04/09/2017
Date
04/09/2012
Author
Stephen Tucker
Original
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Document Number: EDS 08-0121
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Date: 02/07/2015
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
6.2.1
Overview ................................................................................................................... 8
6.2.2
Option 1: HOT Grid/Primary Site Supply from a Dedicated Secondary Substation
Inside the HOT Zone ............................................................................................... 10
6.2.3
Option 2: Dedicated Secondary Substation Outside the HOT Zone ......................... 11
6.2.4
Option 3: RMU Outside the HOT Zone and a Transformer Inside the HOT Zone .... 12
6.2.5
Option 4: Dedicated Secondary Substation Inside the HOT Zone............................ 13
6.2.6
Option 5: Overhead Line – Dedicated Transformer/Substation Inside HOT Zone .... 14
6.2.7
Option 6: Overhead Line – Dedicated Transformer/Substation Outside HOT Zone . 15
6.2.8
Option 7: LV Network using an Isolation Transformer .............................................. 16
7
Installation Requirements ..................................................................................... 17
7.1
Secondary Substation ............................................................................................. 17
7.2
Lead Sheathed Cables ............................................................................................ 17
7.3
Jointing .................................................................................................................... 18
7.4
Miscellaneous Materials .......................................................................................... 19
7.5
Warning Labels ....................................................................................................... 19
8
Operational Requirements .................................................................................... 21
8.1
General ................................................................................................................... 21
8.2
Documentation ........................................................................................................ 21
8.3
Power On ................................................................................................................ 21
8.4
NetMap.................................................................................................................... 22
9
References ............................................................................................................. 23
Appendix A – Examples ................................................................................................... 24
A.1
National Grid Acton Lane 22kV................................................................................ 24
A.2
Rayleigh Main.......................................................................................................... 25
A.3
Norwich Main........................................................................................................... 27
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A.4
Bramford Grid .......................................................................................................... 28
Appendix B – Operational Document .............................................................................. 29
Figures
Figure 5-1 – Process Flowchart ............................................................................................ 7
Figure 6-1 – Supply Options Overview .................................................................................. 9
Figure 7-1 – RMU Cable Sheath Bonding ........................................................................... 17
Figure 7-2 – RMU Cable Sheath Bonding Example ............................................................ 18
Figure 8-1 – Power On HOT Site Annotation ...................................................................... 22
Figure A-1 – LV Supply to National Grid 22kV Substation at Acton Lane ............................ 24
Figure A-2 – LV Supply to National Grid 22kV Substation at Acton Lane ............................ 24
Figure A-3 – Rayleigh 400kV and 132kV Substations ......................................................... 25
Figure A-4 – Rayleigh 400kV and 132kV Substations – Power On Extract.......................... 25
Figure A-5 – Norwich Main 400kV and 132kV Substations ................................................. 27
Figure A-6 – LV Supply to Norwich Main 400kV and 132kV Substations ............................ 27
Figure A-7 – LV Supply to Bramford 400kV and 132kV Substations ................................... 28
Tables
Table 4-1 – EPR Threshold for a HOT Site Classification ..................................................... 6
Table 6-1 – Supply Options Overview ................................................................................... 8
Table 7-1 – Warning Labels ................................................................................................ 19
Table 8-1 – Power On HOT Site Pin Text............................................................................ 21
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1
Introduction
This standard details the additional requirements for the provision of LV supplies to all higher
voltage sites (e.g. 132kV, 33kV etc.) that are HOT or owned by National Grid1. 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.
2
Scope
This standard applies to the provision of LV supplies in EPN, LPN and SPN to UK Power
Networks HOT sites, third party HOT sites and all National Grid sites.
This standard does not apply to supplies to mobile telephone base stations on National Grid
towers which are covered in EDS 08-0030.
This standard is intended for internal and external use.
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
1
Not all National Grid sites are HOT but they should be treated as HOT for the purpose of providing LV supplies
as detailed in this standard.
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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
Normal reliability
430V
Main protection systems that clear the
earth fault current in excess of 200ms
20kV, 11kV, 6.6kV
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 sheath 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 database2 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.
2
UK Power Networks Substation Earthing Database is available from the UK Power Networks Intranet using the
following link Substation Earthing Database.
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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.
Design
Delivery
Network Records
START
Obtain site information (EPR,
HOT zone etc)
(Section 5.2)
Construct substation in
accordance with ECS 06-0023
(Section 7.1)
HV or LV supply?
Isolate HV cable sheaths,
install cables in ducts etc
(Section 7.2)
HV
Select supply option
(Table 6-1)
Design secondary substation
using earthing design tool
(EDS 06-0014)
LV
Apply warning labels
(Section 7.4)
Prepare operational document
(Section 8.2)
Ensure earthing doesn’t
extend outside the HOT zone
Review operational document
with Network Manager and
Operational Safety Manager
(Section 8.2)
Connect substation to main
earthing system of higher
voltage substation
Prepare SAN showing
HOT Site pins
(Section 8.3)
Load operational document
into Alfresco
(Section 8.2)
Design supply with TT earth in
accordance with
EDS 08-0129 or EDS 08-0143
(Section 6.2.3)
Customer to provide isolation
transformer, RCD and earth
(Table 6-1)
Apply pins to Power On
(Section 8.3)
Provide supply from LV
network without an earth
terminal (TT earthing)
Link Power On to operational
document in Alfresco
(Section 8.3)
Apply warning labels
(Section 7.4)
Update NetMap
(Section 8.4)
END
Figure 5-1 – Process Flowchart
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6
Design Requirements
6.1
Information Requirements
The following information 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
Overhead
Line
Dedicated transformer/substation inside HOT Zone
6.2.6
Dedicated transformer/substation outside HOT zone
6.2.7
LV Network
Via isolation transformer
6.2.8
5
6
7
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Option 1: HOT Grid/Primary Dedicated Secondary
Substation Inside the HOT Zone
HOT Grid/Primary Substation
Option 2: Dedicated Secondary Substation Outside the
HOT Zone
HV Network
HOT Site
HOT Site
Supplies Only
R
M
U
HOT Site
Supplies Only
R
M
U
Option 4: Dedicated Secondary Substation Inside the
HOT Zone
Normal
Supplies
HV
Network
HV
Network
HV Earth
LV Earth
HV Network
HV/LV Earth
R
M
U
HV Earth
LV Earth
HV/LV
Earth
Normal
Supplies
R
M
U
Option 3: RMU Outside the HOT Zone and a Transformer
Inside the HOT Zone
HOT Site
HOT Site
Supplies Only
R
M
U
HV Network
HOT Site
HV/LV Earth
HOT Site
Supplies Only
R
M
U
HV Earth
Metalwork/
LV Earth
R
M
U
HV
Network
HV Network
Option 5: Overhead Line – Dedicated Transformer/
Substation inside HOT Zone
HV Overhead Network
Normal
Supplies
HV/LV
Earth
Option 6: Overhead Line – Dedicated Transformer/
Substation Outside HOT Zone
HV Overhead
Network
HOT Site
HOT Site
Pole Tx
Pole Tx
HOT Site
Supplies Only
HV/LV
Earth
HOT Site
Supplies Only
HV Earth
LV Earth
HV Overhead
Network
HV Overhead Network
Option 7: LV Network using an Isolation Transformer
LV Network
HOT Site
Isolation Tx
HOT Site
Supplies Only
LV Earth
LV Network
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
HOT Grid/Primary Substation
4
2
HOT Site
Supplies Only
R
M
U
HV/LV Earth
1
2
7
Normal
Supplies
R
M
U
8m
HV
Network
HV Earth
LV Earth
8
2
1
Notes:
1 - EPR <2kV
2 - Warning labels
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 will not usually be 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
Supply Source
HV Cable
Arrangement
HV
Network
1
HOT Site
4
1
2
2
R
M
U
3
HOT Site
Supplies Only
8m
HV Earth
LV Earth
4
4
4
4
7
8
HV
Network
Notes:
1 - EPR <2kV
2 – Neutral-earth link removed
3 - LV cable installed in insulated duct
4 - Warning labels
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
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 will not usually be required.
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
Supply Source
HV Cable
Arrangement
HV
Network
HOT Site
7
R
M
U
1
5
2
3
HV Earth
4
HOT Site
Supplies Only
Metalwork/
LV Earth
4
5
5
6
HV
Network
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
Application/EPR Limit
Any HOT site where the EPR is less than 12kV
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
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 will not usually be required.
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 sheath bonded to RMU earth and insulated from the transformer
(sheath 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
Requirement
Details
Supply Source
HV Cable
Arrangement
7
4
Normal
Supplies
R
M
U
HV
Network
HV/LV
Earth
HOT Site
3
HOT Site
Supplies Only
R
M
U
2
4
HV/LV Earth
See Figure 8
4
5
3
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
7
HV
Network
R
M
U
4
Normal
Supplies
HV/LV
Earth
Application/EPR Limit
Any HOT site where the EPR is less than 5kV
Type of Supply
Dedicated standard secondary substation located in the HOT zone
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 will not usually be required.
Supply Earthing
Combined HV/LV earth bonded to main site earth
Other Requirements
HV cable sheaths 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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6.2.6
Option 5: Overhead Line – Dedicated Transformer/Substation Inside HOT Zone
Requirement
Details
Supply Source
HV Overhead Line
Arrangement
HV Overhead
Network
HOT Site
7
1
2
Pole Tx
HOT Site
Supplies Only
HV/LV
Earth
HV Overhead
Network
2
4
Notes:
1 - EPR <12kV
2 - Warning labels
Application/EPR Limit
Any HOT site where the EPR is less than 12kV
Type of Supply
Dedicated pole-mounted transformer or ground-mounted substation
located inside the HOT zone
Supply Earthing
Combined HV/LV earth bonded to main 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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6.2.7
Option 6: Overhead Line – Dedicated Transformer/Substation Outside HOT Zone
Requirement
Details
Supply Source
HV Overhead Line
Arrangement
HV Overhead
Network
7
3
HOT Site
1
Pole Tx
2
8m
HV Earth
HOT Site
Supplies Only
LV Earth
3
HV Overhead
Network
4
Notes:
1 - EPR <12kV
2 - Cable installed in insulated duct
3 - Warning labels
Application/EPR Limit
Any HOT site where the EPR is less than 12kV
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
LV
Network
HOT Site
1
Isolation Tx
HOT Site
Supplies Only
2
Notes:
1 - EPR <12kV
2 - Cable installed
in insulated duct
3 - Warning labels
3
LV Earth
3
4
LV
Network
LV Network
HOT Site
Cutout
Isolation Transformer
RCD
3
4
3
Site Earth
HOT Site
Cutout
Isolation Transformer
RCD
3
3
4
Site Earth
Application/EPR Limit
Any HOT site where the EPR is less than 2kV
Type of Supply
EDS 08-0129 or EDS 08-0143 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:




7.2
Installation of HV cable sheath bonding where required as shown in Figure 7-1 and
Figure 7-2.
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.
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.
SW1 (LH) Cable Box
SW2 (RH) Cable Box
RMU
Connector
03196H or
MF15/5/SH
from 02806D
Insulated Earth
Stud Removed
and Blanked Off
Cover
Connector with
Heat Shrink
Cable Sheaths Insulated
from Cable Boxes
Aluminium or Copper Insulated Cable Sheath
Bond Sized to match Earthing System
Heat Shrink
Boot
Figure 7-1 – RMU Cable Sheath Bonding
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Date: 02/07/2015
Figure 7-2 – RMU Cable Sheath Bonding Example
7.3
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.
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7.4
Miscellaneous Materials
Material
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 Screens
Connector
03196H
Connector Straight Thru Main
300 (x3)
02806D
LV 185mm Waveform Pole
Term Direct Connector
7.5
Warning Labels
The warning labels detailed Table 7-1 shall be installed as specified in Section 6.2.
Table 7-1 – Warning Labels
3
No
Situation/Location
Reference
4
(Material Code )
Specification
1
Install in prominent
position inside
fence/enclosure
EDS 07-0009.117
100mm x
150mm
adhesive label
2
In LV cabinet or
micro/compact
EDS 07-0009.118
100mm x
50mm adhesive
label
3
Next to the cut-out
EDS 07-0009.130
100mm x
50mm adhesive
label
(21515D)
(21758H)
4
3
4
Next to the cut-out
EDS 07-0009.131
Label
100mm x
37.5mm
adhesive label
For the availability of labels without a material code please contact the author or refer to EAS 07-0021.
UK Power Networks logistics material code.
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3
No
Situation/Location
Reference
4
(Material Code )
Specification
5
Next to affected
equipment
EDS 07-0009.132
100mm x
37.5mm
adhesive label
6
On substation door
EDS 07-0009.133
100mm x
50mm adhesive
label
7
On substation door
EDS 07-0009.134
100mm x
50mm adhesive
label
8
In LV cabinet or
micro/compact
EDS 07-0009.171
(21517X)
75mm x
110mm
adhesive label
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Label
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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 designer, project manager and senior authorised person 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 to each affected site to highlight
any non-standard earthing requirements. 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.
The relevant information should be included on the System Alteration Notice (SAN) to allow
the diagram to be correctly annotated.
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Figure 8-1 – Power On HOT Site Annotation
8.4
NetMap
On completion of the installation NetMap shall be updated to show:



Insulated cable sheaths.
Sections of overhead line that should not be undergrounded.
Any other bespoke installation details.
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9
References
EAS 00-0002
Cables and Joints
EDS 06-0001
Earthing Standard
EDS 06-0002
HOT Site Requirements (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 08-0030
LV supplies to Mobile Phone Base Stations Mounted on 132, 275
and 400kV Towers (internal document only)
EDS 08-0129
LV Metered Connections up to 100A Single-phase
EDS 08-0143
LV Metered Connections Above to 100A Single-phase
11kV Jointing Manual
HSS 40 050
Controlling Impressed Voltages on Underground Cable Systems
(future HSS document)
National Grid TS 3.1.2
Earthing
National Grid NSI 5
Insulated Working on Cable Systems
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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
240
Gibbons Road
SW1
Panel 48
24843
Acton Ln Opp Waxlow Rd
National Grid
24731
Waxlow Rd Unit A
Centrus
24650
Acton Lne Hamm
Med Res
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.
Rayleigh Main 132kV
Rayleigh GIS Local
and Local 2 11kV
CEGB 400 Grid11kV
Rayleigh Main 400kV
NG Switching Station 11kV
Figure A-3 – Rayleigh 400kV and 132kV Substations
Figure A-4 – Rayleigh 400kV and 132kV Substations – Power On Extract
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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 sheath 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.
Norwich Main 400kV
Norwich Main 132kV
Figure A-5 – Norwich Main 400kV and 132kV Substations
Pole 8
Pole 7
HV Earth
HOT Zone
Norwich Main
400kV
Norwich Main
Dunston
Norwich Main
132kV
HOT Site
Supply 1
Norwich Main
132kV Local B
HOT Site
Supply 2
HOT Site
Supply
HV/LV Earth
HV/LV Earth
Norwich – London Liverpool St Main Line
Orange Mast
Ipswich Road
Normal
Supply
HV/LV Earth
Pole 12
Pole 11A
OHL
Pole 11
Cable
HV Earth
Figure A-6 – LV Supply to Norwich Main 400kV and 132kV Substations
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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 9b
Euromast
Pole Tx
Pole 7b
New
ABSD
Pole 8b
Cable sheath
insulated
from earth
HV cable
in duct
HOT Zone
Bramford Grid
400/132kV
New
Secondary
Substation
Cable sheaths
bonded to
steelwork earth
CEGB 400kV Site
To be removed at
later stage
HV/LV
Earth
HV/LV
Earth
To be removed
when NG
construction
complete
CEGB 132kV Site
Pot
End
Bramford Grid
Temp Supply
Cable sheaths to
be connected to
steelwork earth
Pole 7c
HV/LV Earth
Pole 1c
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 08-0121B.
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