Prestrike characteristics of double-break vacuum circuit breakers with RC hybrid grading methods under DC voltages

Abstract This study presents a systematic investigation into the prestrike characteristics of double-break vacuum circuit breakers under various DC voltage levels, focusing on the impact of different resistor–capacitor (RC) hybrid grading configurations. Experimental evaluations were conducted to analyze the distribution and dispersion of prestrike gaps, floating terminal voltages, and voltage-sharing uniformity across five RC schemes. Compared to traditional capacitive grading, RC hybrid methods considerably improve the voltage distribution symmetry, enhance the low-voltage side voltage proportion, and reduce the dispersion of prestrike gaps. Notably, moderate resistance values (50–100 kΩ) achieve optimal trade-offs between performance and consistency. A mechanism analysis reveals that the resistive element effectively suppresses the reverse capacitor discharge and mitigates imbalances in field emission current, thereby promoting breakdown uniformity. This work presents the first comprehensive evaluation of RC hybrid grading strategies from a DC prestrike perspective, providing both theoretical insights and practical guidance for optimizing high-voltage VCB design and phase-controlled closing strategies.