In order to improve the reliability of a DC vacuum circuit breaker（VCB） for high current interruption

a novel current commutation interruption（CCI） scheme was proposed based on the typical forced commutation. The current fall rate before the VCB arc current zero（ACZ） was remarkably reduced by the current shunting of an auxiliary switch conduction and by decreasing the effective commutation current

and an interval of low transient recovery voltage（TRV） came out through the voltage clamping of the auxiliary switch conduction after the VCB ACZ. Thereby

the vacuum gap post-arc dielectric recovery behavior was improved

and the reliable high DC current interruption process would be realized for medium and high voltages. By analyzing the commutation process of the new scheme in detail

the influences of some main parameters

such as the stray inductance of the commutation circuit

the turn-on moment of the auxiliary switch

on the commutation performance and the influence rules were obtained. Finally

the 13 kA CCI test for a fast VCB was carried out. During the test

the VCB current fall rate before ACZ was effectively reduced to about 55 A/μs

which lasted for about 50 μs in total. And the VCB TRV was limited to less than 600 V within about 130 μs after ACZ. The test results verify the practicability and effectiveness of the new scheme.