To understand the mechanism of space charge accumulation for high-voltage DC outdoor composite insulators

we take the composite insulator in operation as an object to simulate the surface charge distribution on the insulator by using the finite element analysis software COMSOL. Surface conductivity of an outdoor insulator is significantly influenced by local environment

so the surface current density

which is the most important influencing factor for outdoor polymeric insulator

is introduced

and a calculation model is established based on the basic electromagnetic field equation. Simulation results indicate that: the most charge accumulates on a certain area of the interface of umbrella and sheath of the composite insulator

and the charge polarity is the same with that of the adjacent electrode; the charge density on the upper surface of the first umbrella increases while the charge density on the lower surface decreases when the upper surface of the first umbrella at cathode end is partly polluted.