Considerations on the Dielectric Characteristics of a Medium Voltage Vacuum Circuit-Breaker

摘要

The paper presents the results of an investigation on the breakdown voltage of the contact gap and on the capability of clearing in high-frequency (H.F.) currents of a commercial vacuum circuit-breaker (c.b.) operating under 'service conditions'. To assess the breakdown levels, a test program was devised that would take into account the actual sequence of events in service, i.e. making-breaking operations followed by the application of the transient recovery voltage (T.R.V.). The results confirm the dependence of the dielectric withstand capability of the contact gap on the preceding switching operation and allow an evaluation of the expected maximum breakdown voltages and of the corresponding contact breakdown distances, as well as the maximum slope of the H.F. current likely to be interrupted in case of c.b. restriking. (ERA citation 14:017311)