The electric field of gas-solid insulation system will gradually transit from capacitive distribution to resistive distribution under DC voltage. This process is accompanied by the accumulation and dissipation of charges

which may cause the decrease of flashover voltage

but the regularity is still not clear enough. Consequently

the volume charge conductance in solid

ions conductance in gas and interface charge conductance were taken into consideration

so that a charge accumulation model for gas-solid insulation system was established. And the correctness of the model was verified by measuring and simulating the surface potential distribution of a post insulator sample. Moreover

the charge accumulation o

n the surface of basin insulator during the electric field transition process under DC voltage was computed and analyzed. The influence of volume conductivity on charge accumulation characteristics was investigated. The results show that

in the process of electric field transition

the convex surface of the basin mainly accumulates homopolar charges. The electric field intensity near the high-voltage side decreases by 9.4% and the electric field intensity near the low-voltage side increases by 23.5%. The heteropolar charges mainly accumulate in most areas of concave surface and the electric field intensity increases by 5.5%. When the volume conductivity is between 10

-14

S/m and 10

-17

S/m

the convex surface of the basin insulator accumulates homopolar charges

while the concave surface mainly accumulates heteropolar charges. With the further decrease of volume conductivity

the mechanism of charge accumulation on the surface of basin insulator gradually turns to be dominated by gas-side conductivity. And the electric field distortion on the surface of basin insulator is further aggravated. The research in this paper can provide a calculation and analysis reference for the insulation design of DC basin insulators.