The gas-solid interface of tri-post insulators of DC GIL is prone to accumulate charge

cause such faults as discharge or explosion breakdown

and is the critical weak point of the insulation system. However

the tri-post insulators have irregular shape and complex curved surface profiles and are currently lack of effective surface charge measurement methods. As for the research of complex surface contour of the tri-post insulator

a spatial five-degree-of-freedom mechanical device capable of conducting comprehensive potential measurements has been set up. The automatic measurement of the potential on the insulator surface is completed

with a total of 15 120 measurement points and a spatial sampling rate of 0.25 mm

-2

. Furthermore

a surface apparent charge inversion optimization algorithm suitable for asymmetric complex surface structures is proposed by adjusting the boundary conditions and using Wiener filtering. The simulation examples under the same interference conditions show that compared with the traditional surface apparent charge method

the root mean square error of the optim

ization algorithm is reduced by 12.2%

which effectively improves the anti-interference ability of the algorithm. Based on the proposed measurement-inversion method

the surface charge accumulation of DC tri-post insulators under different temperature conditions is studied

finding that the temperature gradient will significantly increase the amplitude and distribution range of the homopolar charges in the leg region of the tri-post insulators

and the surface charge density can exceed 60 μC/m

2

.