Functional gradient EP/BaTiO3 coatings enhancing AC surface flashover voltage of epoxy/Al2O3 spacer

Surface flashover of the insulator triggers gas-insulated switchgear’s unpredictable failure and affects the reliability of the electrical system. However, most studies focus on material modification to reduce surface charge but fail to eliminate the electric field distortion caused by insulator geometry effects. To reduce the structural distortion and improve the AC flashover voltage of the insulator, functional gradient coatings are designed onto the epoxy spacer, coating layer parameters affecting electric field distortion are analyzed, and partial discharge and AC flashover measurements are conducted to verify the design rationality. It indicates that the surface electric field becomes uniform with increasing permittivity, number of layers, thickness, and reasonable height design. Then, a three-layer functional gradient scheme is fabricated onto an epoxy spacer with 0.5 mm coating thickness: 50 wt. % EP/BaTiO3–0.6 mm (height), 40 wt. % EP/BaTiO3–1.1 mm, and 30 wt. % EP/BaTiO3–13.3 mm. The maximum electric field of the design decreases by 54.06% compared to the uncoated sample, and the partial discharge frequency and quantity decrease. The AC surface flashover increases by 17.62% compared to the uncoated spacer, indicating the design effectively reduces field distortion. The findings lay a fundamental foundation for future advanced functional gradient material designs to regulate electric fields for other engineering applications.