Surface Charge and Electric Field Distribution along Tri-post Insulators in ±800 kV GIL

A multi-physics simulation model of the tri-post insulator in ± 800kV GIL laid horizontally is established. Based on the model, the temperature and gas flow distribution inside the GIL are obtained. The surface charge and electric field on the tri-post insulator surface are calculated considering the gas convection. Results show that the maximum temperature gradient reaches 29 K and the gas dielectric strength decreases by 11%. While the greater temperature gradient along the lower post leads to more surface charge injection through insulator buck conduction, which results in more serious electric field. The flashover is more likely to be triggered around the lower post of the tri-post insulator. It is hoped that this study can contribute a useful guide for the design and manufacture of DC-GIL.