The Development Of Partial Discharges Along Oil-pressboard Interface And Their Severity Indicators

Surface discharge is very common in the transformer which mainly as the discharge along the coil surface, screens and the lead wire of tap. For the partial discharge monitoring to transformers, can continuely and real-time reflect the internal insulation deterioration. It is an important way to master the transformer insulation condition. At present, partial discharge monitoring can't combine the partial discharges signals and the insulation failure. Therefore, depth study the development process of surface partial discharge phenomena and laws. This can provide data reference from the scheduled maintenance to state maintenance, and provide areliable guarantee for the decision-making.A non-uniform electrical field discharge was constructed in this paper to simulate the real transformer oil wedge discharge. And the operation condition of the real transformer was also established. A set of joint monitoring platform including conventional impulsive current detection system, ultra high-frequency detection system, broadband pulse current detection system as well as dissolved gas analysis system was established.Applying voltage step by step, we studied the surface discharge pulses current signal and the UHF signals PRPD development. Analized the total magnitude, pulse rate, average magnitude and maximum magnitude. Additionally the development of oil dissolved gas was studied in order to reflect the whole process of the surface discharge. We summed up the principles of the development of the oil wedge. The discharge phase of the division rules was proposed.In this paper, the relationship between the partial discharge and the characteristics and the electrical trees. The Weibull distribution was uesd to search the different electrical trees, the time interval of pulses was also studied corresponding the changes of the pulse waveform. The influence of electrical trees characteristics to the pulses rate was studied.The surface discharge development process is studied from the initial to the breakdown using a variety of methods, get the time span of process of surface discharge and the characteristics of initial stage. Estimate the severity of the discharge and stages, make the formation of the internal surface discharge diagnosis of the transformer and effective early warning rules.