Grid connection to CPP in a deregulated electricity market: A case study related to fault current levels

Abstract

Cost of power is one of the major driving factors for profit margins in any industry. Deregulation of electricity market enhances this opportunity for industry consumers to settle for minimum prices for the same usage of electricity. This leads to restructuring of existing power system networks. Addition of infinite power sources such as grid, demands for a thorough check of design limits of the available switchgear. Thus, short circuit current levels become a deciding factor in importing additional power with existing switchgear. In a Captive Power Plant (CPP), the maximum fault current levels are studied with respect to single phase to ground fault (Line to ground – LG) and three phase short circuit fault. Methods of grounding determine whether LG fault current can exceed the three phase fault current. This becomes necessary as the estimated maximum current is used for deciding the rated short circuit breaking capacity of switchgear. LG fault currents are computed and compared with three phase fault currents at different system voltage levels for a particular CPP where power import from grid is considered. An attempt is made to study the variation of Coefficient of grounding with system grounding resistance for a particular voltage level which is resistively grounded.