Surface Charge Characteristics of DC-GIL Insulator Under Multiphysics Fields: 3-D Modeling

Surface charge accumulation on the insulator of direct current gas-insulated transmission lines (DC-GILs) under thermal-electric multiphysics fields is investigated using the finite element method (FEM). To obtain the accurate temperature and charge distributions in the horizontally installed gas-insulated transmission lines (GILs) with a basin-type insulator, a three-dimensional (3-D) geometric model is constructed. First, the equations and parameters are optimized to improve the computing efficiency. The thermal gradient (TG) negligibly affects the surface electrical conductivity. The recombination and diffusion terms in the ion transport equation can also be removed. After omitting these terms, the calculation efficiency is improved by approximately 70% without affecting the calculation accuracy. The surface charge density increases under TG but varies slightly in different radial directions along the insulator surface. In contrast, the electric field distribution obviously depends on the radial direction. The calculations confirm that the improved method properly analyzes the surface charge characteristics under thermal-electric fields and can thus evaluate the insulation performance of DC-GILs.