Review of the numerical prediction method for the interruption capability of SF ₆ circuit breakers

Numerical prediction methods both for the thermal interruption capability and the dielectric recovery capability of SF ₆ gas circuit breaker (GCB) are reviewed in the paper. The arc conductance 200 ns (G ₂₀₀) before current zero is a key parameter of the thermal interruption capability of the GCB. The magneto-hydro-dynamics (MHD) model is applied during the arcing process and the Mayr model is adopted near current zero to evaluate the G ₂₀₀. Then the arc time constant and the arc power loss coefficient could be obtained. To evaluate the dielectric recovery capability of GCB, the reduced electric field strength E _c has to be calculated everywhere in the interrupter after current zero. The reduced critical electric filed strength E _a has to be computed as well. The probability of the dielectric breakdown after current zero can be judged by the comparison of the E _a and E _c. It has to be indicated that the proposed numerical prediction methods are still need to be verified by further experimental efforts.