Design of Earthing System for a Substation : A Case Study

This paper presents the design of earthing system for 132 KV substation and simulation for calculation of required parameters. This paper is to provide information pertinent to safe earthing practices in ac substation design and to establish the safe limits of potential difference under normal and fault conditions. The grounding grid system of a practical 220 kV substation is calculated by MATLAB program. The supporting data has been obtained from actual field tested at the substation. 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 selection the proper horizontal conductor size, vertical electrode size and soil resistivity, the best choice of the project for safety is performed. This paper mentions the calculation of the desired parameters which are simulated by MATLAB program. Some simulated results are evaluated.