Surface Texture Of PEI Insulation Materials And Its Effect On Vacuum Surface Flashover Performance

Vacuum surface flashover is a kind of discharging phenomenon occurring along the surface of the insulator in vacuum.Generally the flashover voltage is far lower than the breakdown voltage of the vacuum gap or the bulk breakdown voltage of the insulator,which makes it a bottleneck problem of the development of the pulsed power technology.Surface morphology of the insulators is a key influence factor of the flashover voltage.Therefore,it is significant to explore the method of fabricating surface texture(specific microstructure arrays)on the insulators and construct microstructure arrays ranging from tens of microns to hundreds of microns on the surface of insulators to study the influence of the microstructure on the surface flashover voltages of the insulators,which is also meaningful to the optimization of the surface microstructure on the insulating materials,understanding the flashover suppression mechanism and the promotion of the practical application of the surface texture technology.Aiming at improving the vacuum flashover voltage of the PEI insulating materials,laser micro processing method was applied to fabricate micro grooves and honeycomb micro holes on the surface of PEI insulating materials to explore the influence of the surface texture on the surface flashover characteristics of the PEI insulating materials in this paper.Meanwhile,atmospheric plasma was applied to modify the surface of PEI insulating materials to study the changes of the surface morphologies and surface components after plasma treatment and their influence on the surface flashover characteristics.The research results provided new thought and methods to the preparation of high-performance PEI insulators.The main achievements are as followed:(1)Triangular microgrooves were fabricated on the surface of PEI insulating materials by the laser micro processing method.Under the processing of 355 nm UV laser,the influence of laser parameters as scanning speeds,power,defocusing value and et al on the width,depth and the period of the micro grooves were studied.Triangular microgrooves ranging from 50 ?m to 300 ?m were fabricated precisely on the surface of PEI insulating materials.The influence of the microgroove parameters on the flashover voltages of the PEI insulators was tested on the pulsed high-voltage platform and the results showed that the surface voltage withstand strength of the treated insulators increased with the increase of the depth and density of the microgrooves and decreased with the increase of the width of the microgrooves.Approximate160%improvement of the flashover voltages of the PEI insulators was realized when the depth,width and period of the microgrooves were 50?m,40?m and 70?m.(2)For the first time,honeycomb micro hole texture was fabricated on the surface of PEI insulating materials by the application of the laser micro processing method.Honeycomb micro holes with different depth,period and scale ranging from 100 ?m to200 ?m and were fabricated on the surface of PEI insulating materials by the adjustment of parameters of the 355 nm UV laser.The influence rules of the honeycomb micro hole with different structure parameters on the Secondary Electron Emission Yield(SEY)were studied and the results indicated that the construction of honeycomb micro holes on the surface of PEI insulating materials could significantly decrease the SEY of the materials and made the surface flashover voltage of the PEI insulators increase significantly.With the decrease of the scale of the honeycomb,increase of the depth and shortening of the periods the flashover of the insulators showed an increase tendency.Finally,a 150% increase of the flashover voltage was obtained after the optimization of the microstructure.(3)Research of the surface modification on the surface of PEI insulating materials was conducted by the plasma treatment produced ionizing atmospheric air.Influence of the treatment time on the surface component,surface morphologies and surface flashover voltages of the PEI insulating materials were studied and the results indicated that treatment by atmospheric plasma could increase the amounts of the polar groups as C-O and C=O on the surface of PEI insulating materials and produce fluctuating structures making the roughness increase.Changes of the surface components and surface structures made the SEY of the insulator decrease,surface conductivity of the insulator increase and flashover voltages of the insulator increase.The flashover voltages of the PEI insulators treated for 10 s by the plasma could increase over 60%.