Mechanical Stress Affecting Dielectric Properties of Epoxy Resin

Gas-insulated transmission line (GIL)/gas-insulated switchgear (GIS) insulators usually withstand complex mechanical stress and strong electric field. This study investigates the insulation properties of epoxy resin subjected to mechanical stresses ranging from −10 to +10 MPa. The transition of mechanical stress from compression to tension leads to a decrease in the relative permittivity of epoxy resin, accompanied by an increase in conductivity, trap energy, and space charge accumulation. Due to the more pronounced impact of mechanical stress on conductivity than on relative permittivity, the dc electric field distribution of the epoxy insulator undergoes more noticeable changes under different mechanical loads, in comparison to those under ac or overvoltage conditions. Results of this study suggest to account for the impact of mechanical stress when designing an insulator.