In order to further investigate the surface flashover mechanism in vacuum, the surface flashover and electric field distribution of multilayer organic insulation structure are studied and developed based on the previous studies. The samples of multilayer organic insulation structure are prepared by inserting multilayer organic composite material with different relative permittivity between the electrode and the dielectric. Two multilayer organic insulation structures are prepared in this study. One is the cylindrical samples, the other is 45° samples. The impulse (1.2/50 μs) and DC flashover voltages in vacuum are tested, and the electric field distributions of two insulation structures are analyzed by ANSYS. It is found that these two insulation structure could effectively improve the surface flashover performance in vacuum. The results indicate that the highest impulse first flashover voltage of cylindrical samples reaches 65 kV and increases by 25% under im- pulse voltage. The highest first flashover voltage of /c samples reaches 81 kV and increases by 32% under impulse voltage. The results of electric field simulation demonstrate that different mechanisms exist between 45° insulation structure and cylindrical structure.
