Dependence of partial discharge UHF characteristics on metal particel position at insulating spacer in GIS

In this paper, the influence of metal particle position at insulating spacer on partial discharge (PD) characteristics is studied by using the ultra high frequency (UHF) detection method in a 252kV GIS PD experimental platform. The PD inception voltage (PDIV), phase resolved partial discharge (PRPD), phase resolved pulse sequence (PRPS) and UHF signal waveform and its frequency spectrum are investigated with different defect position and under stepped applied voltage amplitude. By combining the electric field analysis of insulating spacer surface and PD investigation results, the influence of metal particle position on PD characteristics is clarified. It is shown that, the PDIV of metal particle defect increases with electric field strength on spacer surface due to the distortion of electric field on surface. The PRPD and PRPS images behave as the floating discharge pattern. The high order modes of EM waves are easier excited when the metal particle placed near the flange of space. The detection sensitivity of extractor-type sensor is much higher than that of external sensor, however it is a little lower than that of interior sensor.