Analysis of Vacuum Arc Characteristics With Double-break DC-VCB on Asynchronous

For 24kV double-break DC vacuum circuit breaker (DC VCB), the arcing process was captured by a high-speed camera and the interrupting current and transient recovery voltage (TRV) were also measured in the process under different gap using an experimental platform. These calculations were analyzed in conjunction with the continuous transition model (CTM), and the arc characteristics, sheath and microscopic characteristics of the two breaks were studied and compared. Furthermore, the electric field strength and power density at the cathode surface were calculated, and the influence of the gap difference on the dielectric recovery was analyzed. The experimental and simulation results show that when there is a gap difference between the two breaks during the current interrupting process of the DB-DC VCB, the arc energy between breaks is unevenly distributed. The narrower break will have a higher arc energy density, higher concentration of metal particles between the contacts, and lower dielectric recovery ability, creating a favorable condition for breakdown. For the 24kV DB-DC VCB, the gap difference between the two breaks that exceeds a critical value has a significant impact. When the gap difference exceeds the critical value, the metal particles between the contacts of fostering the formation of weak breakdown points. When a breakdown occurs, the arc is reignited, which leads to current interruption failure. © 2022 Chin. Soc. for Elec. Eng.