Improved method in calculating the surface charge distribution of DC-GIL insulators with 3D geometry models

Surface charge accumulation is an important issue when dealing with the insulation property of direct-current gas-insulated transmission lines with insulators. An improved method is introduced to calculate the surface charge distribution of insulators based on three-dimensional (3D) geometry models with high solution accuracy and computing efficiency. More than 90% of the computing memory and time are reduced by applying weak form partial differential equation (PDE) to the ion transport equation compared to adding artificial diffusion term. The computing memory and time are further reduced by 70% when removing the diffusion term from the ion transport equation, whereas the accuracy remains unchanged. Thus, the method of combining the modification of ion transport equation and the application of weak form PDE is suggested in calculating the surface charge of 3D geometry models. Finally, this method is applied in calculating the surface charge distribution of a ±200-kV basin-type insulator under thermal-electric coupled fields and a ±500-kV tri-post insulator. Results show satisfying accuracy and efficiency. It is concluded that the proposed method can be applied in analysing the charge accumulation and ion transport behaviour based on 3D models under various operating conditions.