The Electric Discharge Detection Method in the Low Vacuum Region of Vacuum Interrupter

SUMMARY The vacuum circuit breaker (VCB) achieves the high current interrupting capability in the pressure lower than 10 Pa to 5 Pa. When gas pressure increases, the breakdown voltage of a VCB decreases according to Paschen's law, and in the case of small leak, the partial discharge will occur in the VCB and the high frequency electromagnetic waves are radiated. So, we have developed the partial discharge detection system using an antenna with the region from 200 MHz to 300 MHz placed inside the VCB. However, if the partial discharge occurs outside the VCB, the detection system leads to misdetection as the partial discharge inside the VCB. In order to improve the performance of partial discharge detection, the outputs of antenna voltages inside and outside the VCB are investigated.