Calculation of the Spatial Charge Distribution in Ultra-high Voltage Direct Current Transmission Lines Based on Dilute Species Theory

The ion current generated during the operation of UHVDC (Ultra-high Voltage Direct Current) transmission lines has an increasingly prominent impact on the electromagnetic environment. At present, electric field line method and finite element method are commonly used to achieve fine steady-state solution of ion flow field, but the dynamic process of corona discharge is not analyzed. Therefore, based on the dilute species theory, the real-time motion state of charge is considered, and the behavior law of ions in complex flow field and electric field is emphasized. The effect of wind speed on space charge distribution is also analyzed. It provides reference for the electromagnetic environment prediction, control, and evaluation of UHVDC transmission projects. The results show that the microscopic process of positive and negative corona discharge is different. It also shows that the two have different mechanisms for maintaining self-maintained discharge. According to the established ±800kV UHVDC transmission line model, the maximum ion current density near the ground is 32.62nA/m2. Affected by the wind speed, the ground ion current density on the downwind side gradually decreases, while the upwind side gradually increases. When the wind speed is greater than or equal to 3m/s, the ground ion current density on the downwind side decreases to 0.