Prestrike characteristics of non-synchronous closing of double-break vacuum circuit breakers under DC voltages

The phase-controlled switching of vacuum circuit breaker (VCB) can enhance power quality, reduces inrush currents and overvoltages, prolongs switch service life, and improves closing reliability. One bottleneck issue with phase-controlled closing technology lies in its inability to close at an optimal phase due to the dispersive nature of the circuit breaker closing process. The double-break VCB effectively solves the problem of voltage saturation of the single-break VCB and improves the performance of the VCB. However, there is a lack of studies investigating prestrike characteristics such as the prestrike gap and dispersion of double breaks, as well as voltage sharing effect. This paper aims to experimentally investigate and compare the impact of non-synchronous closing on prestrike characteristics, with the goal of developing a method to reduce both prestrike gaps and dispersion in VCBs. The research results show that non-synchronous closing can significantly affect the prestrike characteristics of VCBs by altering the partial voltage distribution and prestrike gap. When the high-voltage side closes 0.2 ms faster than the low-voltage side, it minimizes both the prestrike gap and dispersion, achieving a nearly equal partial voltage ratio of approximately 1:1, which is beneficial for phase control technology. The findings can serve as a theoretical foundation for determining phase-controlled closing strategies.