Identification Structural and Moisture Defect of Oil - Paper Insulation Bushing Based on Partial Discharge Phase and Discharge Quantity Analysis

Partial discharge is one of the important causes for the defect of oil-paper insulation bushings. At present, the traditional dielectric response test is still the main method for the insulation detection of the bushings. It can only perform insulation detection and condition assessment on the entire bushing, but cannot accurately identify the local defects. In order to detect and identify the defect types of oil-paper insulation bushings, this paper designs three kinds of defect bushings, carries out partial discharge tests, and analyzes the partial discharge characteristic parameters respectively. The results show that when the bushing has structural defects, the number of discharge pulses, the maximum discharge and the average apparent discharge will increase significantly with the increase of applied voltage. When the voltage rises to 37.5 kV, some discharge pulses different from the initial discharge will appear during the sampling period, and they are symmetrical in the PRPD spectrum; When the core of the bushing is affected by moisture, the discharge pulses in the PRPD spectrum show obvious “mountain” shape, and the discharge characteristic parameters are also significantly different from the structural defects; When the insulation oil of bushing is affected by moisture, it will hardly cause partial discharge under rated voltage. PRPD spectrum and discharge characteristic parameters can be used to distinguish different types of defects in oil-paper insulation bushings. The results provide theoretical support for promoting partial discharge detection and defect identification of bushings.