Experimental research on partial discharge radiated UHF signal attenuation characteristics in GIS

For detecting partial discharge (PD) phenomenon in gas insulated switchgear (GIS), ultra-high-frequency (UHF) method, which detects electromagnetic wave (EM wave) in UHF band with good immunity to noise, has been widely employed to avoid insulation accidents. In order to deeply understand the propagation process of EM wave and improve the utilization of the UHF method, it is necessary to investigate the attenuation characteristics of UHF signal from broadband PD sensor. In this research, by using the self-designed planar equiangular spiral antenna, the output UHF signal is detected and analyzed experimentally in a 252 kV GIS with L-shaped structure (LS) and disconnecting switch (DS) tank. When DS is closed and is open, the output signal is measured under two applied voltage levels individually in the test. And the results are mainly investigated in detail by time, statistics and frequency analysis. The propagation rules of the peak to peak value (V_pp) and transmission rate of the UHF signal are summarized. This research provides some referential significance towards the rational use of UHF method and better implementation of PD detection.