Residual current analysis by applying ground fault transfer arc suppression method

When a single-phase grounding fault occurs in isolated neutral systems, ground fault transfer, which makes the fault phase directly ground on the bus, can effectively inhibit the intermittent arc overvoltage. However, the influence of this method on residual current and arc extinction lacks essential investigation and validation. In this paper, distribution characteristics of the capacitive current of each feeder and the load current of fault feeder are analyzed. After ground fault transfer, expressions of the residual current at fault point and the current at bus grounding point are given. Then, the variations of residual current with fault location and transition resistance are analyzed. It can be found that the residual current might be enlarged and even exceed the system capacitive current, because part of the load current of fault feeder passes through the bus grounding point, the earth or the cable sheath and the fault point to the load. It is difficult for arc to extinguish. Therefore, phase-to-phase fault would be caused and personal security even be endangered. Finally, the correctness of theoretic analysis is verified by simulations. © 2018, Chinese Institute of Electrical Engineering. All rights reserved.