Prestrike Characteristics of Double-Break Vacuum Circuit Breakers in Making Power Frequency Voltage

Abstract

Vacuum circuit breakers (VCBs) have been extensively employed in switching shunt capacitor banks. However, research on the prestrike characteristics of double-break VCBs in making power frequency voltage remains limited. This study aims to investigate the influence of different closing time differences on the prestrike characteristics of double-break VCBs in making power frequency voltage, and to compare these influences with those of single-break VCBs. Experiments were conducted using vacuum interrupters rated at 24 kV, with contacts made of CuCr40 alloy doped with 1 wt% graphene. Taking the closing time of the high-voltage break as the time zero point, three closing time differences (0 ms, 0.727 ms, and −0.347 ms) were set, and experiments were carried out at six closing phase angles (from 0° to 150° in 30° increments) for each condition. The experimental results demonstrate that when the closing of the high-voltage break lags behind that of the low-voltage break by 0.347 ms, the double-break VCB exhibits optimal prestrike performance, where prestrike is almost entirely suppressed except at the 90° phase angle. Furthermore, the prestrike performance during the closing of the double-break VCB is significantly superior to that of the single-break VCB, characterized by a steeper RDDS curve. These findings provide a theoretical basis for the design of control-switching double-break VCBs.