Propagation Attenuation Properties of Partial Discharge in Typical In-Field GIS Structures

Using the ultra-high frequency method to detect partial discharge (PD) is considered effective for the insulation diagnosis of the gas-insulated switchgear (GIS). In this research, in order to gain a clear understanding of the propagation attenuation property of PD, a 220-kV real GIS is utilized and four types of typical PD sources are designed and fabricated, including floating metal, protrusion, void in solid insulation and particle on the spacer. Three common GIS structures are considered in the paper, which are the straight structure with spacer, as well as the L-shaped and T-shaped structures. The attenuation can be caused by these GIS structures when the PD signal emitted from the defect propagates through them. In this study, research is focused on the variations of the time-domain amplitude, the frequency spectrum, and the cumulative energy of the PD signal. Based on the three aspects, the changes of PD signal through GIS structures are described comprehensively, and the propagation properties are presented in detail. The lowpass ( MHz) and bandpass (800 MHz-1600 MHz) filters are applied to elaborate the propagation property of different frequency bands. Since the characteristics of PD caused by the four types of defects are different, their attenuation properties will also be different. These typical PD sources are tested in each GIS structure, respectively.