Designing of Grounding System of High Voltage AC Substation Using Two Layer Soil Model – A Novel Approach

The main purpose of grounding electrical systems is to provide a suitably low resistance path for the discharge of fault current which ultimately provide safety to working personnel and costly equipments in the substation. The flow of heavy fault current results in rise of potential in the substation area and with respect to remote ground. There is need to ensure that the ground potential rise, and touch and step voltages are within permissible limit. 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. This soil model is derived from the accurate soil resistivity measurement structure at the proposed grid location. This paper provides a overview of 4 pin method for measurement of resistivity & provide the method of single and two layer soil modelling of substation area with help of MATLAB GUI software and provides an example to understand the modelling procedure.