Designing & parametric analysis of grounding system of gas insulated substation (GIS) for multi layered soil model

Abstract

The main objective of grounding system of substation is to provide a low resistance path for the discharge of heavy fault current. This further helps by providing safety to working personnel and costly installed equipments and machinery in the substation. It is essential to curb the flow of heavy fault current which may result in rise of potential in the substation area and with respect to remote ground. Also it is necessary to control the ground potential rise, and touch and step voltages within the permissible limit. The numbers of GIS substations are increasing due to scarcity of space especially in metropolitan cities. Also the level of fault level of substations is increasing with the growth of power system. There is need to provide low resistance path for the discharge of short circuit fault current to ensure safety to working personnel and costly installed equipments in the substation. This in turn helps to keep the ground potential rise, and touch and step voltages within the permissible limit. It is pertinent to mention here that an accurate soil model is required to design grounding system of the substation that ensures that the resistance of the grounding grid through the earth is sufficiently low. Soil resistivity data is of fundamental importance in performing grounding system analyses. Reliable data is required to achieve good correlation between design and measured grounding system performance. Soil model is derived from the accurate soil resistivity measurement structure at the proposed grid location.