ENA Technical Specification 41-24, “Guidelines for the Design, Installation, Testing and Maintenance of Main Earthing Systems in Substations” (a D-Code Annex 1 document) was published in 1992 and is still widely used today. It is now in need of a review and update to account for new technology and developments in International, European and British Standards.
Key documents are:
- IEC/TS 60479-1 “Effects of current on human beings and livestock – Part 1: General aspects”
- IEC/TR 60479-5 “Effects of current on human beings and livestock – Part 5: Touch voltage threshold values for physiological effects”
- BS EN 50522 “Earthing of Power Installations exceeding 1kV ac”
- IEC and EN 61936-1 “Power installations exceeding 1kV ac – Part 1: Common Rules”
- HSE Recommendations to BSI Committee PEL/99 on application of IEC/TS 60479
In parallel, it is proposed to revise ENA Engineering Recommendation S34, “A Guide for Assessing the Rise of Earth Potentials in Substations” which forms some of the background to ENATS 41-24. The work of revision of ENATS 41-24 will be done by a Working Group of the ENA Earthing Co-ordination Group with the assistance of an external Consultant. The Consultant will attend, and provide technical input to, Working Group meetings and carry out background analysis and calculations, inter alia, in the following areas:
- touch step and transfer potentials;
- interpretation of standards in respect of separation of HV and LV earths;
- development of risk assessment methodology.
The calculations will be carried out using the CDEGS software package (including RESAP, MALT, MALZ modules) or equivalent.
Project commencement date: June 2012
Target completion date: 31 December 2016