Design of Earthing System for HV/EHV Substation and its Safety

Abstract

This paper presents the Design of Earthing System for HV/EHV Substation and its Safety; 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 saft 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. Initially significance of Earthing is explained & methodology for design of substation grounding system is discussed for HV / EHV substations. Standard equations are used in the design of Earthing system to get desired parameters such as touch and step voltage criteria for safety, earth resistance, grid resistance, maximum grid current, minimum conductor size and electrode size, maximum fault current level and resistivity of soil. By selecting the proper horizontal conductor size, vertical electrode size and soil resistivity, the best choice of the project for safety can be performed. This paper mentions the calculation of the desired parameters for 400 kV substation.