Study on High Frequency Current Interruption Characteristics of Vacuum Circuit Breaker

It is well known that vacuum circuit breakers (VCB) have such superior characteristics as small size, light weight, small noise, frequent interruption, easy maintenance, and no decomposition products emission. On the other hand, some kind of surge generation may be their only one drawback. Just after the small current interruption with a very short arcing time, a repetitive re-ignition or three phase simultaneous interruption sometimes occurs. Surges related to these phenomena are considered the serious causes of insulation damage of the equipment in distribution power systems. In order to clarify these surge generation mechanisms, we did the experiment on the high frequency (HF) current interruption and the recovery characteristics of VCB with very short arcing time. We investigated the effect of a high frequency current on the dielectric recovery characteristics after the high frequency current interruption by means of synthetic test circuit in short electrode gap. For experiment parameters, we changed HF current frequency, amplitude of HF current values (about 350A and 750A) and impulse voltage (less than 8kV), arcing time(several hundred micro seconds) and delay time of impulse voltage application after HF current interrupted(several micro seconds). In this paper, the result of experiment will be reported.