Earth faults protection circuit in power distribution network - compares residual current polarity with homopolar voltage polarity

摘要

The protection circuit is for earth faults in power distribution networks. It detects the appearance of a homopolar voltage and determines its polarity during a fixed period of time. The residual current present in each phase line is detected during this fixed time and its polarity determined. The homopolar voltage's polarity is compared with the residual current's polarity in order to discover the presence of a fault. If present, this fault is then localised.