Effect of Electrical Tree Deterioration on Field Distribution and Insulation State Evaluation of Epoxy Resin Bushing

Epoxy resin connection bushing is widely used in the field of electrical equipment because of its excellent heat resistance, mechanical properties and electrical insulation properties. However, due to the long-term operation of epoxy resin bushing in complex outdoor environments, it is easy to generate electrical trees under harsh conditions such as humidity and pollution, which gradually leads to insulation deterioration and defects such as discharge and flashover, which seriously affects the reliability of power supply. In this paper, the finite element method and dielectric discharge theory is used to study the electric field distribution characteristics around epoxy resin connection bushing caused by the deterioration of electric tree, and the effect of different ablation depths on the electric field strength around epoxy resin connection bushing is also analyzed. At the same time, the mechanism for the effect of electric tree ablation depth on the field distribution characteristics is expounded. The results show that the electric field strength at flanges of the epoxy resin connection bushing is the largest, which is the weak part of the insulation for the bushing, and the discharge breakdown is most likely to occur here. Meanwhile, the effect of electric trees' position on the electric field distribution is much greater than that of the ablation depth and shape. The results provided in this work can provide theoretical and experimental support for the evaluation of the insulation state of connection bushing, and it is also helpful to engineering operation and maintenance.