Electrical Tree Degradation Characterization of Epoxy Resin under Thermal and Mechanical Composite Stresses Based on Photoelastic Effect

Epoxy resin is extensively utilized in electrical devices for structural support, insulation, and encapsulation, owing to its superior thermal stability, dielectric performance, and mechanical strength. Nevertheless, in compactly designed systems operating under extreme environmental conditions, epoxy insulation materials are prone to thermal-mechanical stress, which may initiate electrical treeing and ultimately compromise insulation reliability. In this paper, photoelastic method was employed to investigate the thermal-mechanical coupling stress dependence of electrical treeing behaviors of epoxy resin. Typical electrical tree growth morphology and stress distribution were observed through photoelastic method. The correlation between tree length and overall accumulated damage with increased mechanical stress value was extracted. The result shows that compressive stress retards electrical tree propagation along the field direction while tensile stress has accelerating effects. Besides, it also proves that the presence of thermal stress can induce more severe accumulated damage.