A practical approach for computation of grid current

When a ground fault occurs at a substation, the part of the fault current that flows between the grounding system and the surrounding earth is known as grid current. This current determines the magnitude of the dangerous voltages within and around the station. It may vary from a few percent to almost 100% of the earth fault current. It is necessary to make an accurate estimate of grid current for an economical and safe design of ground electrode. The available analytical methods for determining the grid current require complete system data, which is voluminous and often unavailable. In this paper a simple and accurate analytical method for determining the grid current is presented. The method requires limited data. A computer program based on the proposed method has been developed and tested.