Computation Of Maximum Earth Current In Substation Switchyards

This paper presents recent developmental advances for the computation of maximum ground potential rise of grounding structures or alternatively maximum earth current in substation grounding systems. An advanced methodology for short circuit analysis is presented. The methodology is based on modeling of power system elements in direct phase quantities. Coupled with equivalency techniques, it provides an extremely efficient algorithm for performing numerous sequential short circuit analyses. An easy to use computer program has been developed under EPRI sponsorship. The computer algorithm uses the methodology to search for the fault condition which yields the maximum earth current in a substation grounding system. The methodology has been validated with actual system measurement on a Georgia Power Company Substation. Validation results are presented. Typical results as well as program utilization factors are discussed. The results demonstrate that the worst fault location is highly dependent on system parameters and cannot be predicted with simple rules.