The influence of additional earthing of healthy phase for earth fault location on safety of compensated networks

摘要

A connection between a phase conductor and the ground in a compensated MV networks is called an earth fault. Since the fault current in this case does not depend on the point of the fault, but only on the total capacity (size) of a network, earth fault location remains a problem for MV network operators. The MV compensated Networks in Czech Republic are operated as nonsymmetrical, that means as networks with non-transposed lines. Some of them are operated with additional earthing of faulted phase for increasing the safety in the point of the fault. The equipment of additional earthing of faulted phase is also able to connect healthy phase for short time. There are fast circuit breakers for additional earthing in the substation and the cycle close-open is shorter than time for tripping of an overcurrent protection in the outgoing feeder-bay (100ms). The paper deals with analysis of the touch voltages in the point of the fault during fault location and describes the experiment in real distribution network.