Sensitivity Calibration of UHF Partial Discharge Monitoring System in GIS

Partial discharge (PD) monitoring system by UHF (Ultra high frequency) method has high sensitivity and high S/N ratio. This UHF PD monitoring system is suitable for PD diagnosis of GIS. Calibration technique of highly sensitive UHF sensor was clarified by injecting the artificial PD pulses. PD sensitivity of each sensor was verified and calibrated results were fully satisfactory. PDs were simultaneously measured with both the conventional method described in IEC-60270 and the UHF PD monitoring system by using many kinds of PD sources and various tank sizes. Owing to this measurement, conversion of dBm units in UHF PD monitoring system to pC units (apparent charge) became possible and it was clarified that the conversion' curve was independent of PD sources and tank size. These characteristics were confirmed by the theoretical analysis.