Influence of extended grading capacitor for suppressing secondary arc on the transient recovery voltage of multi-break circuit breaker

The extended grading capacitor (EGC) is a cost-effective technique to suppress secondary arc. However, whether the use of EGC would weaken the interrupting capability of circuit breakers (CB) or not is still undetermined. In this work, an equivalent circuit model for ultra-high voltage transmission line was established. The expressions of transient recovery voltage (TRV) across the contact gap of CB are derived, and hence the rate of rise of recovery voltage (RRRV). Then, a series of simulations have been performed, including the long-line fault, the short-line fault (SLF) and the terminal fault. It is found that the RRRV had approximately linear downward trend with the increase of the capacitance of EGC under long-line fault but had approximately index downward trend under SLF. The SLF poses the strictest requirements to the CB. In addition to suppressing secondary arc current, the use of EGC would mitigate the interrupting severity and enhancing the interrupting performance of CB.