The Impact of Particles on Post-arc breakdowns in Capacitive Interruptions

The advantage of long electrical life makes vacuum circuit breakers suitable for clearing the capacitive loads. However, the high probability of post-arc breakdowns threatens the safety and reliability of the power system potentially. It is believed that particles generated in the interruption processes are responsible for triggering the breakdowns. The objective of this paper is experimentally observing the generation and dynamics of particles in capacitive interruptions as well as their resultant effects on post-arc breakdown, to further reveal possible mechanisms for particle-induced breakdown. An optical diagnostic platform based on a laser-shadow technique was constructed to detect the particles generated by different electrodes materials. Meanwhile, a 20-kV synthetic test circuit which contained an inrush current source was set up. Particles generation was observed to be closely related to the inrush Currents. Additionally, under the influence of the recovery voltage, particles showed complex and diverse dynamic behaviors, such as bouncing, oscillating, levitating, lifting and deflecting. More importantly, it was found that post-arc re-breakdowns were more likely to occur when particles were close to the electrode at higher recovery voltages. Based on particles behaviors, breakdown moment and recovery voltage, particles were primarily responsible for the long delayed restrikes.