Difference of Partial Discharge Behavior in Large Transformers and Small Defect Model Caused by Capacitance

Partial discharge is an important indicator of the aging of oil impregnated paper insulation, and online monitoring and analysis of it is of great significance for ensuring the safe operation of transformers. However, the existing partial discharge detection methods are mostly based on the equivalent model of gap discharge, ignoring the capacitance effect of the transformer interior, resulting in a large error in the estimation of the discharge amount. In this paper, a three-capacitor model is used to equivalent the oil impregnated paper insulation, and a true-type transformer discharge circuit is built, which is compared with the traditional small model discharge circuit. Using Simulink software to simulate the discharge amount of the two models, the results show that the discharge amount of the true-type model considering the capacitance effect is significantly higher than that of the small model, and the difference between the two becomes larger and larger as the capacitance effect increases. This paper illustrates the importance of considering the capacitance effect for improving the accuracy of transformer partial discharge detection, and provides technical reference for the analysis of the discharge amount of true-type transformers.