BS 7430:2011+A1:2015 Code of practice for protective earthing of electrical installations. ENA Technical Specification 41/24: Guidelines for the Design, Installation, Testing and Maintenance of Main Earthing Systems in Substations. ENA Engineering Recommendation S34: A Guideline for Assessing the Rise of Earth Potential at Substation Site. Electricity Supply Regulations (replaced by The Electricity Safety, Quality and Continuity Regulations 2002. All of our electrical designers are Level 1 accredited users of CDEGS earthing design software.