Prestrike Characteristics of a Vacuum Interrupter in Controlled Switching of Shunt Capacitor Banks

Controlled switching of shunt capacitor banks could effectively moderate the transient electromagnetic impact on the power grid, which requires an accurate making or breaking operation for the engaged circuit breakers. The objective of this study is to experimentally determine the prestrike characteristics of a vacuum interrupter in making against a power-frequency voltage. A 12 kV fast vacuum circuit breaker (FVCB) is used. The closing velocities, defined as an average velocity over a 1/2 contact gap before the contact mating, is set as 1.43 m/s. The transient breakdown voltage values are recorded under different kinds of voltage-wave phase-angle conditions. In each experimental case, the contact of the test vacuum circuit breaker is supposed to metal-mate at different voltage-wave phase angles, which rise from 0° to 150° and are stepped by 30°. Results show that the transient breakdown process in making the power frequency voltage is different from those of gas switches or vacuum interrupters under DC voltage. The latter two methods are traditionally taken as solutions for determining the controlled-making strategy of the capacitor banks. The study contributes to the promotion of the controlled vacuum-switching technology.