Download EMS 10-0602 Earthing Assessment Process

Document Number: EMS 10-0602
Date: 12/09/2016
ENGINEERING MAINTENANCE STANDARD
EMS 10-0602
EARTHING ASSESSMENT PROCESS
Network(s):
EPN, LPN, SPN
Summary:
This document details the process for carrying out earthing assessments as part of
work detailed in maintenance standard EMS 10-0601.
Author:
Stephen Tucker
Date:
12/09/2016
Approved By:
Barry Hatton
Approved Date:
06/10/2016
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 author or owner of the current issue.
Applicable To
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: 1.0
Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
Revision Record
Version
1.0
Review Date
12/09/2017
Date
12/09/2016
Author
Stephen Tucker
New document to cover grid and primary substation assessment process and support the
requirements of EMS 10-0601
Version
Review Date
Date
Author
Why has the document been updated:
What has changed:
© UK Power Networks 2016 All rights reserved
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
Contents
1
Introduction ................................................................................................................4
2
Scope ..........................................................................................................................4
3
Glossary and Abbreviations .....................................................................................4
4
Prerequisites ..............................................................................................................4
5
Process .......................................................................................................................5
5.1
Annual Programme ..................................................................................................... 5
5.2
Planning ...................................................................................................................... 5
5.3
Site Work ..................................................................................................................... 5
5.4
EPR Assessment ........................................................................................................ 6
5.5
Safety Voltage Assessment ........................................................................................ 6
5.6
Review ........................................................................................................................ 7
5.7
Re-design .................................................................................................................... 7
6
Reporting ....................................................................................................................7
7
Invoicing .....................................................................................................................8
8
Review Meetings ........................................................................................................8
9
Audits ..........................................................................................................................8
10
References ..................................................................................................................9
10.1
UK Power Networks Standards ................................................................................... 9
10.2
National Standards ...................................................................................................... 9
11
Dependent Documents ..............................................................................................9
Appendix A – Earthing Report and Drawing Naming Conventions ................................10
A.1
Filename ................................................................................................................... 10
A.2
PDF Properties .......................................................................................................... 11
A.3
Dates ......................................................................................................................... 11
Tables
Table 5-1 – Typical Ground Return Current Percentages .......................................................6
Table 5-2 – Typical Fault Clearance Times .............................................................................6
Table A-1 – Filename Format ................................................................................................10
Table A-2 – PDF Properties ...................................................................................................11
Table A-3 – Date Format .......................................................................................................11
© UK Power Networks 2016 All rights reserved
3 of 11
Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
1
Introduction
This document details the process for carrying out earthing assessments at primary and grid
substations as part of work detailed in maintenance standard EMS 10-0601.
The highly technical nature of this work generally requires the services of a specialist
earthing contractor/consultant to carry out the measurement, site survey, modelling and
assessment activities to ensure safety voltage limits are acceptable and the substation can
be classified as safe.
2
Scope
This procedure applies to all primary and grid earthing survey and assessments carried in
accordance with EMS 10-0601 in EPN, LPN and SPN.
3
Glossary and Abbreviations
Term
Definition
Alfresco
UK Power Networks document management system
COLD Site
A site where the EPR is less than or equal to 430V or 650V (for high
reliability protection with a fault clearance time less than 200ms)
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
HOT Site
A site where the EPR is greater than 430V or 650V (for high reliability
protection with a fault clearance time less than 200ms)
NetMap
UK Power Networks graphical information system (GIS)
PowerOn
UK Power Networks network management system (NMS)
4
Prerequisites
The following are required to carry out the work detailed within this document:
•
•
•
•
Suitable earthing measurement equipment.
CDEGS (Current Distribution, Electromagnetic Fields, Grounding and Soil Structure
Analysis) licence.
UK Power Networks substation entry up to 132kV.
Access to UK Power Networks IT systems including Earthing Database, NetMap,
PowerOn, Alfresco PowerShare and Alfresco EnterpriseShare.
© UK Power Networks 2016 All rights reserved
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
5
Process
5.1
Annual Programme
J
F
M
A
M
J
J
A
S
O
N
D
Planning
Site Work
Assessments
Reports
Review Meetings
5.2
Planning
Before the site visit:
1. Review existing earthing information including the earthing database, Alfresco
PowerShare and any previous design and assessment reports.
2. Obtain substation earthing layout drawing and/or site layout from UK Power Networks.
3. Determine suitable measurement routes using geographical maps of the surrounding
area and NetMap.
4. If required identify the landowner using the Land Registry web site and notify the
landowner of the intent to carry out measurements. Notify UK Power Networks of any
access problems.
5. Request any other required information from UK Power Networks or third parties e.g.
National Grid.
6. Examine PowerOn system to identify any operational restrictions and plan accordingly.
5.3
Site Work
5.3.1
General
All site work shall be carried out in accordance with HSS 40 xxx.
5.3.2
Measurements
Review any existing earthing measurement records. Where required carry out soil resistivity
measurements and/or a fall-of-potential earth resistance measurement as specified in
EMS 10-0601 and ECS 06-0024.
5.3.3
Earthing Survey
Carry out an earthing survey as detailed in EMS 10-0601 and record the results on form
ECP 11-0406.
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
Create a drawing of the main parts of the existing earthing. Record and any defects found
during the survey and note the different types of surface covering found in and around the
substation.
Provide a report (based on EMS 10-0601a format) containing the soil resistivity
measurement results, measured earth resistance, a list of defects and continuity
measurements.
5.4
EPR Assessment
An assessment of the EPR shall be carried as follows:
1. Analyse the circuit data from NetMap to determine the supply details and the fault
current data provided by UK Power Networks to determine the ground return current
using the approach detailed in ENA ER S34. Ground return reductions to account for the
current returning via the cable sheaths can be applied in accordance with Table 5-1.
Table 5-1 – Typical Ground Return Current Percentages
Voltage
Ground Return Current (Igr)
132kV
34.5%
33kV
23.3%
11kV or 6.6kV
37.4%
2. Calculate the EPR from the measured earth resistance and the calculated ground return
current.
3. Classify the site as HOT or COLD in accordance with ENA ER S36.
5.5
Safety Voltage Assessment
An assessment of the safety voltages shall be carried out as follows:
1. Create a CDEGS computer model of the existing substation earth electrode from existing
drawings and/or the findings of the survey (Section 5.3.3).
2. Carry out an assessment of the touch and step potentials using the approach in
BS EN 50522 (a similar approach is being incorporated into the next revision of
ENA TS 41-24).
3. Check the calculated touch and step potentials against the tolerable limits in
ENA TS 41-24 using the typical fault clearance times detailed in Table 5-2.
Table 5-2 – Typical Fault Clearance Times
Voltage
Fault Clearance Time
132kV
0.2s
33kV
0.5s
11kV or 6.6kV
1.0s
4. If unsafe check using BS EN 50522 tolerable limits.
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Earthing Assessment Process
Document Number: EMS 10-0602
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Date: 12/09/2016
5. If unsafe request site specific protection settings and check against ENA TS 41-24 and
BS EN 50522 limits.
6. If unsafe request fault current data based on the measured site resistance. For 132kV
substations request detailed fault current data, with vector format, per-phase current
flows on each line and transformer, to allow neutral currents to be subtracted.
7. Review the measured earth resistance and check if correct. Calculate the value for a
safe site using the existing surface type including any surrounding cable network and
include in report.
8. If unsafe review with UK Power Networks and then produce an earth electrode redesign
to address the issues.
9. Add a summary of the main findings to the report.
5.6
Review
Review all reports at a bi-monthly meeting with UK Power Networks.
5.7
Re-design
If the initial assessment of the touch and step potentials (Section 5.5) exceeds the tolerable
limits carry out a substation re-design as outlined below:
1. Design an earth electrode system to accommodate any new plant, integrate with the
existing earthing and bring the earthing of the substation in line with current UK Power
Networks earthing standards (EDS 06-0013).
2. Provide the proposed earthing design in AutoCAD format drawn on an equipment layout
drawing provided by UK Power Networks.
3. Add the proposed earth electrode to the CDEGS model.
4. Calculate touch and step potentials across the proposed arrangement for the fault
clearance times provided. If necessary, make refinements to the design to ensure that
touch and step potentials are within ENA TS 41-24 tolerable limits.
5. Produce contour plots showing the touch and step potentials across the site for the
proposed earthing arrangement. Plot the HOT zone, if applicable, based on an outline
model of the substation cable network.
6. Add a summary of the main findings and the above plots to the report.
6
Reporting
All completed test forms and reports shall be provided in pdf format.
All drawings shall be provided in MicroStation or AutoCAD and pdf format.
All reports and drawings shall use the filename and pdf property naming convention
specified in Appendix A.
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
7
Invoicing
Each activity shall be listed as a separate invoice item based on the agreed contractual
rates.
Invoicing shall be tracked on a spreadsheet in a format agreed with UK Power Networks.
This will include the activities undertaken at each substation, the invoice amount and a total
for each operational area and comparison to the purchase order total.
8
Review Meetings
Regular review meetings shall take place, e.g. every two months and will normally involve
the following attendees:
•
•
•
•
UK Power Networks’ project manager.
UK Power Networks’ health and safety representative.
UK Power Networks’ procurement representative.
Contractor project manager.
A typical agenda for the review meeting is as follows:
•
•
•
•
•
•
•
•
•
•
9
Introductions and housekeeping.
Safety message.
Review actions.
KPIs.
Health and safety.
Audit findings.
Progress review.
Invoicing.
AOB.
Date of next meeting.
Audits
UK Power Networks shall carry out a regular audit of the site assessment team to ensure the
procedure outlined in HSS 40 057 is being followed. The contractor is also responsible for
undertaking audits of their own staff.
Any issues raised during the audits shall be reported at the review meetings and resulting
actions captured as part of the meeting actions with responsibility apportioned.
© UK Power Networks 2016 All rights reserved
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
10
References
10.1
UK Power Networks Standards
EDS 06-0013
Grid and Primary Substation Earthing Design
ECS 06-0022
Grid and Primary Substation Earthing Construction
ECS 06-0024
Earthing Testing and Measurements
EMS 10-0601
Earthing Inspection, Assessment and Maintenance
EMS 10-0601a
EPR Assessment Report
ECP 11-0406
Earthing System Test Form
HSS 40 057
Substation Earthing Assessment
10.2
National Standards
ENA TS 41-24 1
Guidelines for the Design, Installation, Testing and Maintenance of Main
Earthing Systems in Substations
ENA ER S341
A Guide for Assessing the Rise of Earth Potential at Substation Sites
1
ENA ER S36
Procedure to Identify and Record HOT Substations
BS EN 50522
Earthing of Power Installations Exceeding 1kV AC
11
Dependent Documents
The documents below are dependent on the content of this document and may be affected
by any changes.
EMS 10-0601
1
Earthing Inspection, Assessment and Maintenance
Available from www.energynetworks.org.
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Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
Appendix A – Earthing Report and Drawing Naming Conventions
A.1
Filename
All earthing reports and drawings shall use relevant filename convention specified in Table
A-1.
Table A-1 – Filename Format
Item
Format
Structure
<substation name> <voltage> Earthing <type> (<report number> <revision
number>)
Substation Name
From earthing database in title case
e.g. Brighton Town
Voltage
All voltages on-site separated by dashes
e.g. 11kV, 33-11kV, 132-33-11kV etc.
Type
Earthing EPR Assessment Report
Earthing Survey & Assessment Report
Earthing Layout Drawing
Earthing Layout Drawing – Proposed
Report Number
Unique report of drawing number in brackets
Version or Revision
Number
Not required for original versions, include in brackets with report/drawing
number
e.g. r1, rA etc
Examples:
Brighton Town 132-33-11kV Earthing EPR Assessment Report (ESL000000-R01).pdf
Brighton Town 132-33-11kV Earthing Survey & Assessment Report (ESL000000-R01).pdf
Brighton Town 132-33-11kV Earthing Survey & Assessment Report (ESL000000-R01
rA).pdf
Brighton Town 132-33-11kV Earthing Layout Drawing (ESL000000-D01).pdf
Brighton Town 132-33-11kV Earthing Layout Drawing - Proposed (ESL000000-D02).pdf
© UK Power Networks 2016 All rights reserved
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Earthing Assessment Process
Document Number: EMS 10-0602
Version: 1.0
Date: 12/09/2016
A.2
PDF Properties
The File and Title pdf properties should follow the convention specified in Table A-2 to allow
trouble free uploading into Alfresco. The pdf properties can be displayed via File >
Properties however these may have originated from the source document or drawing file.
Table A-2 – PDF Properties
Property
Content
File
Match filename
Title
Blank
A.3
Dates
All dates shall use the format specified in Table A-3. Ordinals e.g. th, st, rd etc. shall not be
used in dates.
Table A-3 – Date Format
Location
Format
Tables
dd/mm/yyyy
Main body
dd mmmm yyyy
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