The reignition characteristics of double vacuum interrupters in series after interrupting vacuum arcs

Vacuum circuit breakers are extending their applications from low/medium voltage level to high voltage level due to their good properties. Multi-break vacuum circuit breakers are used in special applications because thry have better breaking capability and withstand higher breakdown voltage compared with single-break vacuum circuit breakers. The objective of this paper is to investigate the reignition characteristics of double VIs in series after interrupting vacuum arc. Two 24kV VIs, which have axial magnetic field contacts and can interrupt a rated short circuit current of 31.5kA, were connected in series. The experiments were carried out in the synthetic circuit providing transient recovery voltage (TRV) with a peak value of 85 kV and a interrupted current of 5 kA. The arcing time was 1ms corresponding to the contact gap 1.2mm. The TRV across VIs were measured by voltage dividers. The results showed that the upper VI was reignited at first due to its higher TRV caused by stray capacitances and then led to the reignition of the lower one. The breaking capability of the double VIs in series was determined by the dielectric recovery of the upper VI and the minimum recovery time was about 2μs.