Discrimination of partial discharge electromagnetic signal in SF 6 gas from external noises using phase gate control method

The authors propose the “phase gate control method” for distinguishing the frequency spectrum of electromagnetic waves caused by partial discharges (PD) in SF₆ gas from external noise. They investigated the dependence of the polarity and phase angle of AC voltage on the electromagnetic wave spectrum. They derived the frequency region where the PD spectrum caused by SF₆ gas can be detected under noisy conditions. They also related, quantitatively, the gain of the electromagnetic wave spectrum to the maximum PD charge simultaneously occurring in both SF₆ gas and air. On the basis of these results, they determined the minimum detectable PD level in SF₆ gas under noisy conditions as a function of measuring frequency