Investigation of Arc Characteristics of a DC Vacuum Circuit Breaker With Double-Break Under Asynchronous Interrupting

A 30-kV direct current vacuum circuit breaker with double-break (DB-DC VCB) in series was taken into consideration; the interrupting current and the transient recovery voltage (TRV) under both synchronous and asynchronous interrupting conditions were measured, and the arcing process during the interrupting was captured by a high-speed camera. The continuous transition model (CTM) was used to simulate the postarc dielectric recovery characteristic during the asynchronous interrupting. The experimental and simulation results show that when one of the breaks in the DB-DC VCB is delayed under 5-kA current interrupting due to the dispersion performance of the mechanism, the two breaks will exhibit a significant difference in the arc characteristic and the TRV. The delayed break has higher arc energy, higher concentration of vaporized metal particles (VMPs), and lower postarc dielectric recovery capacity. The different break gap widths during the arcing process led to the arc characteristic difference. When the delay exceeds a critical value (0.5 ms), the VMPs between the break for the delayed break are difficult to dissipate and easy to reignite at the breakdown weak point.