The novel DC hybrid vacuum circuit breaker based on forced commutation principle is effective for fault protection in DC power system with small time factor. The realization of a rapid DC vacuum circuit breaker（VCB） depends on the knowledge of the high current interruption characteristics of a vacuum circuit breaker in the condition of short arcing duration and short gap. In this study

a synthetic test circuit was used to study the dielectric recovery of a VCB with Cu Cr50 butt contacts after interrupting 20 kA DC currents in the condition that the arcing time was hundreds of microseconds and the contact gap was not more than 2 mm. Experiment results showed that for interrupting the current of 17 kA with the decline rate of 110 A/μs

the VCB could still withstand electric field strength of 10 kV/mm after dielectric recovery time of 41 μs

but delayed dielectric breakdown happened at times. When the interrupted current increased to 21 kA

the broken-down electric field strength was below 5 kV/mm. The interruption performance of VCB can be improved by using new contact structure to get multiple-column arc ignited at the moment contacts opening.