The effects of increased fault current on the existing substation grounding system : A case study

Abstract

The aim of this research is to investigate the effect of increased fault current on an existing substation grounding system. Increased load demands because of the new customers connecting on the existing network or reconfigured network, power flows on the transmission and distribution assets will increase, which will in turn trigger the increase in fault current levels, both three-phase and phase-to-ground, throughout the power system. The protection that ground grids provide against step- and touch potentials is only good up to the expected level and duration of ground fault currents, as originally communicated in the design phase. A case study is presented in this research project to investigate the effects of increased fault current on the existing Ruighoek distribution substation grid. It is found that, the ground potential rise and touch potential are aggravated by the increased fault currents. And by increasing the area occupied by the ground grid and decreasing the horizontal spacing of parallel conductors, stepand touch potentials are improved to safe limit as per IEEE Std. 80-2000.