Post-Arc Transient Dielectric Recovery Characteristics of Vacuum Interrupter in the Large-Capacity Generator Circuit Breaker

Abstract

Large-capacity generator circuit breaker (GCB) based on vacuum interrupter technology is the key power equipment to ensure the safe operation of the power system. When the short-circuit current was forced to cross zero, the large-capacity GCB was difficult to generate a zero-voltage environment through freewheeling, the vacuum interrupter (VI) would immediately withstand the transient recovery voltage (TRV), and there was a lack of research on the post-arc transient dielectric recovery characteristics. First, an experimental platform for transient dielectric recovery characteristics was built, which was capable of generating TRV quickly after current-zero with the voltage rise rate (du/dt) of about 20 kV/μs. The large current post-arc dielectric recovery tolerance experiments with the peak current of 100 kA were carried out, and the post-arc tolerance process was divided into three modes according to the TRV waveform. The influence of arcing time, residual current and current change rate (di/dt) on the transient dielectric recovery characteristics was investigated. Next, we found that the transient dielectric recovery of VI under the same conditions was characterised by dispersion. The influence mechanisms of ‘active regulation of the vacuum arc’ and ‘consistency of the arcing process’ on the dispersion of the transient dielectric recovery were studied in detail. The ‘safety boundary’ consisting of the minimum of dielectric recovery strength was analysed, and the optimal arcing control strategy was proposed. The design basis of the circuit breaker was obtained. Finally, a prototype GCB based on vacuum six-breakers in parallel and current transfer was developed, and the large short-circuit current had been successfully broken, which verified the post-arc transient breaking reliability of the VI. The conclusions will lay the foundation for the engineering application of high-capacity GCB.