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Technical Specification for Secondary Substation Earthing

Technical Specification for Earthing and bonding at Secondary substations EART-03-003 Issue No. 1 SP Power Systems Limited Page 1 of 64 1. SCOPE This Technical Specification describes SPEN s requirements for Earthing and bonding systems at Secondary substations. This includes all HV/LV substations, HV switching stations, HV pole-mounted installations and HV customer substations up to and including 11 kV. It is intended for application to new build or existing substations where significant work is carried out on site ( switchgear replacement or transformer change), and is not retrospective.

This specification allows SPEN to demonstrate compliance with relevant national and international standards as well as statutory legislation and licence conditions. This document has been issued to align with latest releases of the ESQCR, BS EN 50522, ENA TS 41-24 and ENA EREC S34. This document replaces EART-02-003. 2. ISSUE RECORD

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Transcription of Technical Specification for Secondary Substation Earthing

1 Technical Specification for Earthing and bonding at Secondary substations EART-03-003 Issue No. 1 SP Power Systems Limited Page 1 of 64 1. SCOPE This Technical Specification describes SPEN s requirements for Earthing and bonding systems at Secondary substations. This includes all HV/LV substations, HV switching stations, HV pole-mounted installations and HV customer substations up to and including 11 kV. It is intended for application to new build or existing substations where significant work is carried out on site ( switchgear replacement or transformer change), and is not retrospective.

2 This Specification allows SPEN to demonstrate compliance with relevant national and international standards as well as statutory legislation and licence conditions. This document has been issued to align with latest releases of the ESQCR, BS EN 50522, ENA TS 41-24 and ENA EREC S34. This document replaces EART-02-003. 2. ISSUE RECORD This is a Reference document. The current version is held on the EN Document Library. It is your responsibility to ensure you work to the current version. Issue Date Issue No. Author Amendment Details 25th Feb 2020 1 Kevin Butter Stephen Batten Eric Paalman This document replaces EART-02-003.

3 This document is significantly different to EART-02-003 to reflect changes to ESQCR, BS EN standards and ENA Technical Specifications 3. ISSUE AUTHORITY Authors Owner Issue Authority Name: Kevin Butter Title: Lead Engineer Substations Group Name: Stephen Batten Title: Lead Engineer Substations Group Name: Eric Paalman Title: Lead Engineer Engineering Design Name: Fraser Shaw Title: Substation Manager Name: Fraser Ainslie Title: Head of Engineering Design and standards 4. REVIEW This is a Reference document which has a 5 year retention period after which a reminder will be issued to review and extend retention or archive.

4 5. DISTRIBUTION This document is part of the Construction Virtual Manual maintained by Document Control but does not have a maintained distribution list. This document also is published to the SP Energy Networks website. Technical Specification for Earthing and bonding at Secondary substations EART-03-003 Issue No. 1 SP Power Systems Limited Page 2 of 64 6. CONTENTS 1. SCOPE .. 1 2. ISSUE RECORD .. 1 3. ISSUE AUTHORITY .. 1 4. REVIEW .. 1 5. DISTRIBUTION .. 1 6. CONTENTS .. 2 7. REFERENCE AND RELATED DOCUMENTS .. 4 8. DEFINITIONS .. 5 9.

5 FOREWORD .. 7 Legacy practice for Earthing at Secondary substations .. 7 Modern practice for design of Earthing at Secondary substations .. 7 Standard Earthing Arrangements .. 7 10. INTRODUCTION .. 8 Earth Fault Current .. 8 Earth Potential Rise (EPR) .. 8 Touch Potential .. 9 Step potential .. 12 Transfer Potential .. 12 Stress Voltage .. 13 Equipment bonding .. 13 Target Resistance .. 13 Network Contribution .. 14 Global Earthing System (GES) .. 15 11. FAULT CURRENTS APPLICABLE TO DESIGNS OF Earthing SYSTEMS .. 17 Functional requirements (Ratings of HV Earthing Conductors and Earth Electrodes).

6 17 Safety requirements (Calculation of EPR for Touch Potentials and Step Potentials) .. 18 12. EPR LEVELS AND LIMITS FOR STEP AND TOUCH POTENTIALS .. 19 13. Substation Earthing DESIGN PROCEDURE .. 23 Preliminary Design Approach .. 23 Design process flowcharts .. 23 Ground mounted substations .. 27 Pole mounted installations .. 27 Network Contribution .. 27 Standard Earthing scenarios .. 29 14. STANDARD Earthing ARRANGEMENTS .. 31 HV Earthing 31 LV Earthing Conductors .. 31 Bonding Conductors .. 32 Buried Earth Electrodes .. 32 Ground-mounted substations.

7 33 Pole-mounted installations .. 41 Technical Specification for Earthing and bonding at Secondary substations EART-03-003 Issue No. 1 SP Power Systems Limited Page 3 of 64 15. INSTALLATION REQUIREMENTS .. 50 General .. 50 Earth Electrode system .. 50 Main Earth Bar .. 50 Cable sheaths/screen 50 Metallic fences and gates .. 50 Metallic doors .. 51 Pole-mounted installations with surge arresters .. 51 Pole-mounted equipment with operating mechanisms accessible from ground level .. 51 Pole-mounted equipment with operating mechanisms not accessible from ground level.

8 51 16. SPECIAL SITUATIONS REQUIRING ADDITIONAL PRECAUTIONS .. 52 Secondary substations in high risk areas .. 52 Provision of building services/ auxiliary supplies to High EPR sites .. 52 Secondary substations located within a grid or primary Substation .. 53 Secondary substations near railways .. 53 Secondary substations near pipelines .. 53 Lightning protection systems .. 53 Non-standard Earthing arrangements .. 54 17. MEASUREMENTS, TESTING AND INSPECTION .. 54 General .. 54 Inspection .. 54 Earth resistance measurement .. 54 18. Earthing DESIGN DOCUMENTATION.

9 55 19. ASSESSMENT OF THIRD-PARTY DESIGNS AND ICPS .. 55 20. GUIDANCE FOR IDNOS .. 55 21. BASIS OF DESIGN .. 55 Scenario (1) - Dense large urban network ( Cities and large towns) - all underground modern cable network .. 56 Scenario (2)- Smaller towns- all underground modern cable network .. 57 Scenario (3) - Rural ground-mounted Substation - all underground modern cable network .. 57 Scenario (4)- Rural ground-mounted Substation (small town) fed from overhead line with Network Contribution .. 58 Scenario (5) - Rural ground-mounted Substation , all/part overhead fed, no Network Contribution.

10 59 Scenario (6) Pole-mounted Substation .. 59 Determination of Legacy Network Contribution .. 59 22. SPECIFIC DESIGN APPROACH GROUND-MOUNTED SUBSTATIONS .. 61 Soil resistivity .. 61 Network Contribution .. 62 Ground Return Current and EPR .. 62 23. ADDITIONAL EARTH ELECTRODES .. 62 Technical Specification for Earthing and bonding at Secondary substations EART-03-003 Issue No. 1 SP Power Systems Limited Page 4 of 64 7. REFERENCE AND RELATED DOCUMENTS This Specification makes reference to, or implies reference to, the following documents.


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