PD pattern of various defects measured by UHF external sensor on 66 kV GIS model

Partial discharge detection in UHF band is more effective because it detects electromagnetic wave with high S/N ratio. We used external sensor on GIS tank in order to detect partial discharge signals. External sensor is used to detect leaked EM wave signals from insulation spacer of GIS tank. In this paper, we conduct experiment in 66 kV GIS model with metal type (MT) spacer and leaked EM wave will be investigated using spiral type sensor without any filter and amplifier. Then, we performed PD pattern measurement. We estimated peak to peak value (Vpp) and the transmission rate of electromagnetic wave emitted by PD. The results showed us that PD pattern is unique for each defect, so every defect has its own characteristics that differ from each other. Then, based on the results we can distinguish kind of defects clearly.