Current-zero measurements of vacuum circuit breakers interrupting short-line faults

Abstract

Current zero measurements are performed during short-line fault interruption tests of vacuum circuit breakers. This switching cycle is characterized by a very steep transient recovery voltage. High-resolution measurements of near current-zero arc current and voltage were carried out. Various reignition modes (occurring between 0 and 75 ms after current zero) were observed due to insufficient arcing time or current in excess of the short-circuit breaking current. The relationship between post-arc current/charge, reignition mode, and transient recovery voltage is discussed in this paper. In addition to the classical post-arc current, already described in the literature, another late post-arc current was observed reaching values up to several tens of amperes after severe thermal arcing stress. All interrupters interrupted at the first or second current zero under the rated conditions of short-line fault current and transient recovery voltage.