Study on surface discharge of nonlinear conductive epoxy resin/SrTiO3 composites in 80–300 K temperature zone

Bisphenol F epoxy resin (EP) is often used in terminal current lead insulation of superconducting equipment because of its good insulation performance, high mechanical strength, good toughness at cryogenic temperatures, and resistance to cold shock and heat shock. However, due to the wide temperature range of 80–300 K and the strong electric field, the EP-N₂ interface is prone to surface flashover, resulting in terminal insulation failure. To improve the reliability of the current lead insulation, non-linear conductive EP/strontium titanate (SrTiO₃) composites were prepared by modification with nano filling. The changes of dielectric, surface discharge, flashover, and trap distribution characteristics of composite materials were studied, and the mechanism of SrTiO₃ on the surface flashover of composite materials was analysed. The results show that the conductivity of the composite increases with the rise of SrTiO₃ filling content, and the amplitude of improvement is greater under the strong electric field, showing a more significant non-linearity. The composite has a lower trap energy level and a greater number of shallow traps compared to pure EP, which accelerates surface charge de-trapping and reduces charge accumulation, effectively enhancing the discharge and surface flashover voltage of the composite.