Dielectric strength of series-connected triggered vacuum switches

An HV switching device consisting of two series-connected triggered vacuum switches (TVS) of type RVU-43 is tested. This device is intended for operation at a voltage up to 80 kV and its maximum switched current is 200 kA. The breakdown voltage of each TVS is measured separately and that of the series connection presented. Weibull plots are used to analyze the breakdown test results. Our investigations allow the determination of experimental and theoretical distribution functions for the breakdown voltages of the individual switches and the combined switching device. The probability of breakdown of the switching device is calculated using empirical distribution functions of breakdown voltages of each TVS. A comparison of the calculated distribution function of the breakdown voltages of the switching device with the experimental distribution function shows good agreement. The proposed method allows estimating the dielectric strength of the switching device depending on the degree of nonuniformity of the voltage distribution between series-connected TVSs.