eds 06-0001 earthing standard.pdf
TRANSCRIPT
Document Number: EDS 06-0001
Version: 3.1
Date: 22/08/2012
TH
IS I
S A
N U
NC
ON
TR
OL
LE
D D
OC
UM
EN
T,
TH
E R
EA
DE
R M
US
T C
ON
FIR
M IT
S V
AL
IDIT
Y B
EF
OR
E U
SE
ENGINEERING DESIGN STANDARD
EDS 06-0001
EARTHING STANDARD
Network(s): EPN, LPN, SPN
Summary: This standard outlines the earthing design and construction requirements for the distribution network at all voltage levels and the associated substations.
Originator: Stephen Tucker Date: 22/08/2012
Approved By: Barry Hatton Approved Date: 28/10/2011
Review Date: 27/10/2016
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 originator of the current issue.
Document History
(The document history notes below are intended as a guide only and may not cover all of the changes. If you wish to make use of this document it should be read in full.)
Version Date Details Originator
1.0 31/03/2008 Original Stephen Tucker
2.0 31/03/2011 Reviewed and updated to reflect the new Earthing Design Manual and Earthing Construction Manual structure
Stephen Tucker
3.0 30/09/2011 Revised to reflect the reclassification of Earthing Manual into design and construction standards
Stephen Tucker
3.1 22/08/2012 COLD and HOT site definitions corrected. Reviewed for publishing on G81 website
Stephen Tucker
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 2 of 7
Contents
1 Scope ..............................................................................Error! Bookmark not defined.
2 References..................................................................................................................3
3 Definitions...................................................................................................................4
4 Application..................................................................................................................4
4.1 New Substations ......................................................................................................... 4
4.2 Existing Substations.................................................................................................... 4
5 Background ................................................................................................................5
6 Earthing Design..........................................................................................................5
7 Earthing Construction ...............................................................................................6
8 HOT Sites ....................................................................................................................6
9 Substation Earthing Database ..................................................................................6
10 Further Advice............................................................................................................7
Tables
Table 1 – Earthing Design Standards ......................................................................................6
Table 2 – Earthing Construction Standards .............................................................................6
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 3 of 7
1 Introduction
This standard outlines the earthing design and construction requirements for the distribution networks and the associated substations.
2 Scope
This standard applies to:
New electrical installations at all voltage levels from 230V to 132kV. Existing substations where there is a material alteration or a substantial increase in earth
fault current.
3 References
This document should be read in conjunction with the following references:
EDS 06-0002 – HOT Site Requirements (internal document only)
EDS 06-0003 – HOT Site Register
EDS 06-0004 – Earth Fault Loop Impedance Requirements (internal document only)
EAS 06-0011 – Earthing Materials
EDS 06-0012 – Earthing Design Criteria
EDS 06-0013 – Grid and Primary Substation Earthing Design
EDS 06-0014 – Secondary Distribution Substation Earthing Design
EDS 06-0015 – Pole-Mounted Equipment Earthing Design
EDS 06-0016 – LV Network Earthing Design
EDS 06-0017 – Customer Installation Earthing Design
EDS 06-0018 – NetMap Earthing Information System (internal document only)
ECS 06-0022 – Grid and Primary Substation Earthing Construction
ECS 06-0023 – Secondary Distribution Network Earthing Construction
ECS 06-0024 – Earthing Testing and Measurements
ECS 06-0025 – Earthing Inspection and Assessment (internal document only)
ENA TS 41-24 – Guidelines for the Design, Installation, Testing and Maintenance of Main Earthing Systems in Substations
ENA ER S34 – A Guide for Assessing the Rise of Earth Potential at Substation Sites
ENA ER S36 – Procedure to Identify and Record HOT Substations
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 4 of 7
National Grid TS 3.1.2 – Earthing
4 Definitions
Term Definition
EPR Earth Potential Rise
COLD Site A substation where the EPR is less than 430V or 650V (high reliability protection)
HOT Site A substation where the EPR is greater than 430V or 650V (high reliability protection)
NAMP UK Power Networks Network Asset Management Plan
ROEP Rise of Earth Potential
5 Application
5.1 New Substations
The following shall be carried out at all new substations:
Design a suitable earthing system in accordance with this standard. Determine the earth potential rise at the substation and update the substation earthing
database accordingly (refer to EDS 06-0002).
5.2 Existing Substations
The following shall be carried out prior to all major asset refurbishment, replacement or extension works at a grid or primary substations irrespective of whether the fault levels are predicted to change:
Carry out an earthing survey and assessment to confirm the suitability and integrity of the existing earthing system
Determine the earth potential rise at the substation and update the substation earthing database accordingly (refer to EDS 06-0002).
Design a suitable earthing system in accordance with this standard. Rectify any deficiencies highlighted by the survey.
Note: These requirements may be excluded where robust records can demonstrate a survey and assessment was completed in the last five years, the existing earthing system is appropriate, the substation earthing database is up-to-date and the remaining service life will match that of the new plant and equipment.
A provision shall be included in a project to cover the costs associated with the design of the earthing system including the survey, assessment and any measurements. However any remedial works associated with an existing earthing system shall be covered by the appropriate maintenance NAMP line.
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 5 of 7
6 Background
When a fault occurs on an electricity transmission or distribution network, it is possible for a large current to flow in the general mass of earth. This current can cause a considerable rise in potential on earthed metalwork, which may be accessible to the public and staff, particularly those who are carrying out fault switching. In addition, without adequate safeguards, it is possible for this excessive rise in potential to be transferred onto adjacent power cables and communication cables creating potential danger to anyone who might be in contact which may be some distance from the actual fault. It is therefore essential that the earthing and bonding arrangements for equipment associated with public electricity supply is properly designed, correctly installed, and regularly tested and maintained.
Therefore the function of earthing and bonding is to:
Provide a low impedance path to enable earth fault current at any point on the network to be returned to the transformer or generator neutral, without thermal or mechanical damage to the connected equipment, and to enable protection equipment to operate correctly.
Limit the voltage rise on all metalwork and the surface of the ground to which persons
have normal access, to a safe value under all reasonably perceived conditions for faults at each voltage level associated with the substation. The earthing system should be constructed so as to prevent the establishment of dangerous potential differences between parts of the substation, which a person may be contacting simultaneously.
7 Earthing Design
The earthing design standards and their application are based on ENA TS 41-24/1 and ENA ER S34/1 but include the requirements of other standards, where this is considered appropriate. Experience gained from assessments and measurements at a large number of substations has also been taken into consideration and has led to some practices being recommended that are contrary to the guidance in the current standards. Also, to ensure a consistent approach at sites shared with National Grid, the appropriate practices have been included from NGTS 3.1.2. The criteria for designing earthing systems are outlined in EDS 06-0012.
When designing earthing systems it is important to recognise that they perform differently at high frequency than at power frequency (50Hz). The standards are mainly concerned with power frequency performance but some specific designs have been included, where appropriate, to cater for high frequency aspects.
Earthing design shall be carried out in accordance with the Engineering Design Standards (EDS) detailed in Table 1.
Note: For any area of earthing not covered by the UK Power Networks earthing standards refer to the guidelines detailed in ENA TS 41-24.
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 6 of 7
Table 1 – Earthing Design Standards
Description New Earthing Design Standard
Old Earthing Design Manual
Old Earthing Manual
Earthing Design Criteria EDS 06-0012 Section 2 Section 2
Grid and Primary Substation Design EDS 06-0013 Section 3 Section 3
Secondary Distribution Substation Earthing Design EDS 06-0014 Section 4 Section 5
Pole-Mounted Equipment Earthing Design EDS 06-0015 Section 5 Section 6
LV Network Earthing Design EDS 06-0016 Section 6 Section 7
Customer Installation Earthing Design EDS 06-0017 Section 7 Section 7
NetMap1 Earthing Information System EDS 06-0018 Section 8 n/a
8 Earthing Construction
Earthing construction shall be carried out in accordance with the Engineering Construction Standards (ECS) detailed in Table 2.
Table 2 – Earthing Construction Standards
Standard New Earthing Construction Standard
Old Earthing Construction Manual
Old Earthing Manual
Grid and Primary Substation Earthing Construction ECS 06-0022 Section 2 Section 4
Secondary Distribution Network Earthing Construction
ECS 06-0023 Section 3 Section 5
Earthing Testing and Measurements ECS 06-0024 Section 4 Section 8
Earthing Inspection and Assessment ECS 06-0025 Section 5 Section 9
9 HOT Sites
The requirements for identifying and recording HOT sites together with the remedial action is detailed in EDS 06-0002. EDS 06-0002 also includes the obligations to third parties and details of the HOT site register (EDS 06-0003).
10 Substation Earthing Database
The substation earthing database contains the earthing related data for all grid and primary substations together with the substation classification. Refer to EDS 06-0002 for further information.
1 UK Power Networks GIS system.
Document Number: EDS 06-0001
Version: 3.1
Earthing Standard
Date: 22/08/2012
© UK Power Networks 2012 All rights reserved 7 of 7
11 Further Advice
Specialist advice on all aspects of earthing is available from Engineering Standards in Asset Management.