Investigation of Partial Discharge Characteristics in Switchgear Bushings

The paper is devoted to partial discharge measurement and analysis in switchgear bushings. PD bushing structure analysis is described to assess possible defect sources in bushings. An experimental 10 kV bushing sample with the natural defect was obtained from the bushings’ manufacturer. It was tested using the PD measurement technique. Test results showed significant PD intensity at voltages from 12 kV and higher. We had an assumption that a part of registered discharges occurred in the air close to the high voltage electrode sharp edges. To check this assumption we grinded them off and repeated the test. The second test did not show considerable PD characteristics change. Therefore, we assume that the bushing sample had an inner defect because the bushing’s surface was not contaminated to generate surficial discharges. The bushing was researched by a destroying method for defect localization. However, inside the bushing, possible defect locations were not found. It might be connected with the fact that the defect could not be found visually at the test time or the defect was located in the gasket between the high voltage electrode and insulator’s body. Besides, determined features of phase-resolved partial discharge patterns in switchgear bushings.