Aging State Evaluation of Transformer Oil-paper Insulation based on PDC Asymmetric Current

The PDC test is an important means to evaluate the main insulation status of the transformer. When the traditional PDC test current is used to analyze the aging state, it is found that there is an obvious asymmetry between polarization and depolarization current, which will affect the accuracy of the evaluation results. Therefore, this paper has carried out research on the asymmetric PDC variation law of oil-paper insulation. Several groups of oil-paper insulation models with different degrees of aging were prepared in the laboratory environment. Under the polarization voltage, the change law of the transient electric field distribution in the aging model was calculated. According to the traditional interface polarization theory, the influence of insulation aging on the traditional interface polarization behavior is analyzed. Finally, this paper uses the collapsible charge model to explain the causes of PDC current asymmetry. Finally, the quantitative characterization relationship between the amount of decomposing charge and the aging of oil-paper insulation was established. The research results of this paper provide theoretical support for improving the accuracy of insulation state assessment of oil-immersed power equipment based on the PDC testing method.