Particle Aggregation State Affecting Insulation Breakdown Characteristics of Epoxy/Al₂O₃ Composite Under Temperature Gradient

Epoxy/Al2O3 composite is widely used in high-voltage gas insulation equipment and cable terminals because of its excellent heat resistance, mechanical properties, and dimensional stability. The settlement of micrometer alumina (Al2O3) during casting and curing of epoxy composite, together with the coupling effects of high electric field and temperature gradient, can significantly affect the electrical breakdown behaviors of the insulation components. In this article, the electrical breakdown characteristics of epoxy/Al2O3 composites under different temperature gradients are tested, and a phase-field simulation model of epoxy/Al2O3 composites with needle-plate electrodes is established. The influences of particle aggregation states on the breakdown characteristics under temperature gradient are analyzed. The results indicate that the breakdown process is accelerated with the increase of temperature gradient, while the high content of Al2O3 particle, especially the aggregation near needle electrode, can suppress the electrical breakdown of the composites. It is believed that the particle aggregation can change the development route of electrical tree channels and affect the overall breakdown time of composites.