A Novel Technique for Detecting Electromagnetic Waves Caused by Partial Discharge in GIS

For the insulation diagnosis of gas-insulated switchgear (GIS), it is necessary to detect partial discharge (PD) under noisy conditions and to specify the direction of electromagnetic wave radiation due to PD. We propose the "phase gate control method" for discriminating the electromagnetic waves caused by PD in SF6 gas from external noises. The proposed method enables us to discriminate PD of about 100 pC in SF6 gas from external noises of more than 10,000 pC in air. We also compare polarization characteristics of electromagnetic waves radiated from PD with those from a half-wave dipole antenna and estimate the radiation length of electromagnetic waves caused by PD. The results derived in this paper will contribute greatly to the insulation diagnosis of GIS on site.