Energy Of Partial Discharge Pulse In Oil-paper Insulation Based On The Distributed Voltage Signals

Partial discharge is regarded as one of the reasons that cause the insulation failure of transformer. Many factors can lead to partial discharge which will gradually erode the cardboard and make the insulation fail. For example, the carbonized traces generated by partial discharge is a common cause of transformer accident, and it greatly shortened the effective insulation distance which decreases the insulation performance of cardboard and makes the breakdown or flashover happen. On the basis of previous studies, this paper is intended to describe the emergence and development of the carbonized traces in oil-paper insulation by partial discharge energy, and focuses on the theoretica analysis of the principle of distributed potential measurement, the calculation of the location and magnitude of space charge, and the calculation method of energy which is based on the three capacitance model.As the starting point of this paper, the study shows the misunderstanding that the energy formulas W=∑ui△qi brings to researchers, i.e. the energy of each pulse discharge equals to the product its instantaneous value of applied voltage and the the apparent amount of discharge, and the energy is zero when the instantaneous equals zero. This paper makes the point that the space charge producted by discharge has an impact on the calculation of the discharge energy. And as the research objectives, it’s necessary to study how to accurately calculate the discharge pulse energy and how to determine the length of carbionized traces. By engraving a groove on the quartz glass plate, this paper artificially limits the developing direction of carbonization channel, eliminating the interference of other directions. And with the help of the distributed potential measurement system, the changes of the electric field under the carbonization channel in different spatial locations can be observed, which is significant to help us study the relationships between the carbonized traces, the space charge and the partial discharge pulse energy.By combining simulation and actual measurement, this paper makes effective supplement and validation to the calculation of repeated discharge pulse energy including its scope of application and method of usage, proposes a more precise method to calculate the location and amplitude of the space charge, and gives a method for determining the length of the carbonized traces which is based on the amplitude of laber frequency component of the distributed potential signal. The results of the constant voltage test showed that, the calculation for the location of the space charge is correct which is consistent with theoreticl expectations, the development distance of carbonized traces can be largely characterized by the final position of the space charge; the space charge has a certain range varying proportional relationship with the apparent discharge magnitude; and the energy calculation method is correct whose trend is consistent with the apparent amount of discharge.