Single line-to-ground faults on distribution systems: Effect of pre-fault voltages on fault currents

This paper presents a numerical study of the pre-fault operation condition effect on the short-circuit currents estimation in distribution systems using symmetrical components. A case study is presented comparing results between ATP/EMTP program and the symmetrical components method, where several loads and pre-fault conditions are considered. The results show that for unbalanced systems, the consideration of 1 pu as pre-fault voltages, can provide reasonable state estimation. Still, for balanced systems the pre-fault condition only is significant when it is used 1 pu as pre-fault voltage, and the load of the system is very high.