Examination of Single-phase Partial Discharge Monitoring Device for Partial Discharge Diagnosis on Three-phase GIS

This paper deals with partial discharge induced electromagnetic wave investigation on three-phase GIS using UHF method and the application of single-phase partial discharge monitoring device (PDM) on three-phase gas insulated switchgear (GIS). The PD source is a protrusion at different positions on the conductor or on the tank. Frequency and phase spectrums of EMW signals emitted by PD at different positions were observed. The most dominant frequency of EMW signal in three-phase GIS was estimated from the cutoff frequency (fc) formula for single-phase GIS. The main difference in frequency spectrum between three-phase and single-phase GIS was found to be the shift of fc to the lower value for three-phase GIS. The presence of three conductors can be considered as increase in an equivalent radius of three-phase conductor by a factor of 1.6 for this GIS model. The phase of PD phase pattern in the phase spectrum depended on the particle position. The PD sources on three-phase GIS were diagnosed by single-phase PDM device. The success rate of diagnosis results is low. The error is predicted to be caused by error in phase recognition of PD pattern. The change in phase shift setting of PD phase pattern in PDM device based on the phase angle of applied voltage at maximum electric field gave better diagnosis results. Index Terms: three-phase, GIS, PDM device, phase shift setting, success rate