The Influence of Grading Capacitor and Commutation Capacitor on the Breaking Process of Multi-break Circuit Breaker

With the rapid development of DC transmission and distribution systems in the medium and high voltage field, medium and high voltage DC circuit breakers have received extensive attention. In order to reduce the high voltage borne by a single break, the multi-break circuit breaker is usually connected in parallel with the grading capacitor on both sides of the break to improve the voltage distribution of each break. Although the use of grading capacitor can greatly improve the voltage distribution between breaks, it also has a certain influence on the breaking process. In this paper, the hybrid three-break DC circuit breaker is modeled and simulated, and the breaking process is analyzed by changing the grading capacitor and the commutation capacitor. The simulation results show that during the commutation process, the increase of the commutation capacitor will accelerate the decrease of the switching branch current. In the rising process of the break voltage, the smaller grading capacitor will produce a larger reverse voltage and a faster rising speed; a smaller commutation capacitor will produce a smaller reverse voltage. At the same time, during the rise of the break voltage, the charging of the grading capacitor will cause the voltage oscillation, which can be suppressed by reducing the commutation capacitor.