Dielectric recovery behaviors after low current interruption measured by submicrosecond voltage impulses

Dielectric recovery behaviors after current extinction have a decisive influence on the performance of a vacuum circuit breaker (VCB) because it ultimately determines the interruption capacity of the VCB. In order to understand the dielectric recovery behaviors, submicrosecond voltage impulses peaked at 90kV with a rate of rise of ~6×10⁸kV/s were applied upon a pair of electrodes in vacuum interrupters. The electrodes were butt type and they were made of Cu and CuCr25, respectively. The contact diameter was 12mm. The arc current frequency was 50Hz and the arcing time was about 9ms. The results showed that the breakdown voltage in the dielectric recovery processes plateaued between 50kV to 80kV from 10μs to 60μs after current zero for Cu contact material at peak arc current 1500A and the breakdown voltage was between 70kV to 90kV for CuCr25 contact material. Moreover, arc current varied from 550A to 2500A (peak value) had no significant effect on the mean breakdown values of Cu and CuCr25 contact materials.