Optimal Design of Grounding System for HV/ EHV Substations in Two Layered Soil

Successful operation of entire power system depends to a considerable extent on efficient and satisfactory performance of substations. Hence substations in general can be considered as heart of overall power system. In any substation, a well designed grounding plays an important role. Since absence of safe and effective grounding system can result in mal-operation or non-operation of control and protective devices, grounding system design deserves considerable attention for all the substations. Grounding system has to be safe as it is directly concerned with safety of persons working within the substation. Main purpose of this work is designing safe and cost effective grounding systems for HV / EHV substations situated at such locations where soil of the substation site is not uniform. Here soil is considered to be horizontally stratified into two layers. Initially significance of two layered soil model is introduced and design methodology for design of substation grounding system is discussed. Next, two design problems have been solved by using newly developed software and results obtained here are verified with the help of Ground Grid Systems module of ETAP – professional software. Comparison of the results obtained by both the software shows nice agreement of the results given by ESGSD with those obtained from ETAP. Hence this software is found to be quite satisfactory tool in the field of design of grounding system for HV / EHV substations. Keywords— Earthing, Earth electrodes, Ground grid, HV/EHV substations, Power systems, Programming, Safety