Investigation of the Evaluation of the PD Severity and Verification of the Sensitivity of Partial-Discharge Detection Using the UHF Method in GIS

The measurement of partial discharge (PD) using ultra-high frequency (UHF) method is considered an effective approach to monitor the online condition of the equipment, which is used to facilitate the detection of incipient defects in gas-insulated switchgear (GIS). In this paper, in order to assess the severity of PD defects using UHF method, the actual 220-kV GIS were subjected to experimentation. The PD was measured simultaneously by using the UHF method and the IEC60270 measurement technique. The combined measurement has been carried out on different defects in PD test cells, including the floating metal, metallic protrusion, and void in epoxy resin. The inner coupler installed in the GIS tank, and the outer coupler placed outside the spacer, are used to measure the UHF signal. The relationship of the apparent charge and the amplitude of the time-domain signal, and the integral energy from 300 MHz to 1.6 GHz of the signal induced by PD in GIS are analyzed thoroughly. In this way, the severity of PD can be quantified using the UHF signal. In addition, to verify the sensitivity of the UHF detection method, a pulse generator with a rise time of about 500 ps is designed. The GIGRE method for the verification of sensitivity, which is used worldwide, is applied in the experiment. The results of the pulse generator experiment are compared to the results produced by the actual discharge sources, and several possible approaches of improving this method are proposed.