Study On The Relationship Of The Carbonization Traces And The Partial Discharge In The Oil-impregnated Paper Insulation

Large oil-immersed power transformers usually adopt oil-paper insulation structure. Partial discharge inside the insulation causes the pressboard carbonization so that the effective insulation distance reduces, which is closely related to the severity of defects. Simple carbonization traces were realized by artificial restriction to study the partial discharge degradation effect on the pressboard.Based on the PD test platform with multi samples, a needle-plate electrode model was constructed in this paper to simulate the real transformer partial discharge. And a wide-band measuring system and oscilloscope input path protector were built to measure the partial discharge signals. Moreover, a visual optical system was established to achieve the real-time observation and restoring of discharge phenomenon.In this paper, by means of acquiring conventional pulse current signals and wideband pulse current signals, the needle-plate discharge model was studied by ladder booster method,and the relationships between different lengths of carbonization trace and partial discharge pulses were analysed. Furthermore, the variation trends of characteristic quantities under each voltage level are contrasted.Preliminary results show that the carbonization trace increased with the the total discharge, and the curves showed two linear relationships of the two stages. And its length had a great relationship with the large discharge pulses. What’s more, the characteristic quantities and scatter diagrams appear to different trends, and the discharge stagnation was observed in the discharge development process. The amplitude and frequency of the discharge in the negative axis increased significantly When the board was near the breakdown. All these results offer the experimental foundation for the further research on the pressboard deterioration processing under the neddle-plate in the oil-papei system.