Influence of Dynamic Charge Compensation on Voltage Distribution of Double-Break Vacuum Circuit Breakers

The grading capacitor is a conventional method to guarantee the uniform voltage distribution (VD) of double-break vacuum circuit breakers (VCBs). However, the main shield voltage unevenness problem of each vacuum interrupter drew little attention in previous study. This article focused on the voltage sharing of the main shield and designed a novel grading capacitor pattern. A dynamic charge compensation (DCC) theory was proposed, which was derived from the novel grading capacitor pattern. Subsequently, an equivalent circuit model, which contained the influence of the DCC, was established for dynamic VD of double-break VCBs. The tests were performed in a synthetic test circuit, and VDs with different grading capacitors patterns were compared, respectively. The results showed that the novel grading capacitor pattern could not only improve the main shield VD but also enhance the effect of balancing the VD ratio between interrupters. The images of cathode spots extinction process correlated the initial condition with postarc sheath growth process. With 83-pF grading capacitors, the compensation effect could reach nearly 50%. Theoretical analysis and test results show the feasibility of the novel grading capacitors pattern, which provides a candidate to put VCBs toward transmission voltage.