Influence of Epoxy Resin Interlayer Interfaces on Electrical Tree Growth and Breakdown Characteristics

The solid–solid insulation interface structure is a typical interface in extra-high-voltage power equipment, in which the multilayer epoxy resin material is a key component in the insulation structure of the power equipment, and the study of its interface characteristics is the most important. In this paper, epoxy–epoxy cross-linking interface specimens were prepared through experiments, and the degree of cross-linking between the interfaces was analyzed by changing the ratio of the curing agent and adding hydroxyl-terminated liquid nitrile rubber (HTBN) particles; it can be concluded that there exists a weak cross-linking reaction between the interfaces. The electrical tree measurement and alternating current (AC) breakdown test platform were set up, and three different cases of no interface, the electric field direction parallel to the interface, and the electric field direction perpendicular to the interface were tested, through which it was concluded that the existence of the interface inhibited the development of the electrical tree. For the three different cases of AC breakdown tested, it was concluded that the presence of an interface enhances the AC breakdown strength when the electric field direction is parallel to the interface and decreases the AC breakdown strength when the electric field direction is perpendicular to the interface through the interface, affecting the charge transport.