Evaluation of high-voltage circuit breaker performance with a validated arc model

A digital current-zero measuring system was used to monitor about 200 zero crossings of short-line fault currents in three designs of commercial high- voltage circuit breakers. The breakers were subjected to standard IEC 60056 tests in a high-power laboratory. With these results, an empirical are mod el was derived, based on the series connection of three classical modified Mayr models. It was found that only three 'free' parameters, extracted from the are voltage and current during the prezero period can describe the sta te of the breaker after each test. With this model, the mat-gin of the inte rrupting capability could be directly obtained. A strong relation between t his margin and the are conductivity at current zero can be established. Ind ependent of arcing time, arcing current and state of the breaker, it was fo und that the current zero conductivity must decrease to 1-2ms (only dependi ng on the design of the breaker) to make a successful interruption possible .