Investigation on Metal Oxide Varistors in DC Circuit Breakers

This paper deals with metal oxide varistors (MOVs) in direct current (dc) circuit breakers (DCCBs). Two significant features of the MOVs are studied. First, the manufacturing parameters of MOVs are reviewed, and impacts of various main and dopant materials on the electrical parameters of MOVs are explored. Breakdown voltage and leakage current are primarily considered under different ceramic semiconductor materials. Second, MOVs’ practical issues in DCCBs are discussed. Results show that MOVs bring reliability issues in DCCBs and significantly reduce the voltage utilization rate of the main switch. Experiments of 375 V/100 A are conducted to reveal thermal runaway failure in MOVs and highlight the corresponding reliability issue.