A novel technique for detecting electromagnetic wave caused by partial discharge in GIS

For the insulation diagnosis of GIS, it is necessary to detect partial discharge (PD) under noisy condition and to specify the direction of electromagnetic wave radiation due to PD.We proposed “phase gate control method” for discriminating the electromagnetic wave caused by PD in SF6 gas from external noises. The proposed method enabled us to discriminate PD of about 100 pC in SF6 gas from external noises of more than 10 000 pC in air.We also compared polarization characteristics of electromagnetic wave radiated from PD with those from a half-wave dipole antenna, and could estimate the radiation length of electromagnetic wave caused by PD. The results derived in this paper will make a great contribution to the insulation diagnosis of GIS on-site.