Under high voltage stress

the electric strength of surface insulation system configured with compound dielectrics is far lower than the breakdown strength of its insulating material

which is closely related to its electric field distribution.The electric field distributions of typical surface insulation structures in vacuum was simulated

such as the parallel flat plate

planar and stick-plate electrode systems.Such influential factors were considered as the gap of electrode-dielectric contact

the coning angle of circular truncated cone

the height of planar electrode

and the dielectric constant of insulator

etc.The simulation results reveal that the contact gap results in the enhancement of local electric field and the change of its direction

more serious distortion of electric field will occur with larger contact gap

conical angle and dielectric constant or smaller electrode hieight.This conclusion will be helpful to the design of surface insulation structure in vacuum.