Prestrike characteristics and mechanism of double-break vacuum circuit breakers under high-frequency capacitive inrush current

This paper presents a systematic experimental investigation into the prestrike phenomena and underlying mechanisms in double-break vacuum circuit breakers during capacitive switching operations. The study focuses on the prestrike characteristics under high-frequency inrush currents of 5 kA and 20 kA. It innovatively elucidates the influence of inrush current amplitude on key parameters, including the prestrike gap length, electric field strength, inrush current chopping behavior, arcing time, and field emission properties of the contacts. Experimental results demonstrate that a high-amplitude inrush current (20 kA) significantly increases the prestrike gap length (with the d₉₀ value increasing by approximately 2 mm) and reduces its dispersion (by up to 40 %) compared to the 5 kA condition. Furthermore, this condition reduces the frequency of inrush current chopping but prolongs the arcing time. Additionally, the high-energy inrush current leads to a notable increase in the field enhancement factor of the contact surfaces, indicating more severe surface degradation. This research provides crucial experimental evidence and theoretical support for the optimized design and engineering application of double-break vacuum circuit breakers in phase-controlled switching.