Effect of Surface Modification on Trap Distribution and Vacuum Surface Flashover of Polymeric Materials

The trap parameter and its distribution could significantly affect the surface flashover of insulation mateirials in vacuum. To further understand the influence of traps on flashover, the surface trap parameters were regulated by surface modification. Firstly the atmospheric pressure plasma jets (APPJ) were used to treat the fluorinated ethylene propylene (FEP) film to control trap density, and electron beam irradiation was used to change surface trap energy level of polymer. Then effect of different processing conditions on the insulation properties of material surface was studied. The trap parameters were tested and calculated by means of isothermal surface potential decay (ISPD), and space charge distribution in FEP film body was also measured by means of pulsed electro-acoustic (PEA). At last surface flashover experiment under DC and pulsed voltages in vacuum was performed. The results show that the trap density of FEP surface increases while the trap energy level becomes shallow after APPJ processing. The space charge has a positive correlation with the trap density. The trap level and density increases after electron beam irradiation with different treatment time. The increase of trap level and trap density could improve the vacuum surface flashover voltage to a certain degree by surface modification.