Dedicated circuit breaker for UHV capacitor bank must meet the breaking requirement for large shortcircuit current

and ensure absence of breakdown after breaking small current. In this study

the cold dielectric recovery and insulation characteristics of different arc interrupter structures were analyzed and compared to determine the best interrupter structure. The breaking characteristics for rated 1.6 k A small short-circuit current and 40 k A large current were calculated. Test circuit was built to measure the values of breakdown voltage under different open distances. The results showed that: 1)The arc ring structure enhanced the electric field of the arc contacts

resulting in the decrease in recovery speed of breaking dielectric and breakdown margin;2)The shield structure shielded the electric field distribution between arc contacts; and 3)The shorter the small current arcing time

the smaller the breakdown margin

so it is necessary to keep the arcing time longer than 0.5 ms to ensure a large breakdown margin. The predicted minimum arcing time for breaking short-circuit current was 15 ms.Calculated results agreed with the experimental data. Since the breakdown points in the test are dispersive

breakdown may occur within 0.5 ms after breaking

so arc extinguishment should avoid this time range.