Investigation of the Effects of Ion Diffusivity on the Ion Flow Field Simulation

The flow of ions near the ground level is an aspect that must be considered in the HVDC transmission line. In this work, we present the use of ion diffusion in the simulation of the 2D ion flow field for reduced and full models of monopolar transmission lines. The simulation includes a ground zone and utilized a high diffusion coefficient for the zone. The charge density, potential, and flow problems are simulated by using a fluid dynamic software with the upwind finite volume method (FVM). The purpose is to investigate the ion charge density near the ground surface. Our results show that the artifact accumulation of charge and the higher current density near the air-ground surface can be mitigated by using the high diffusion coefficient of the ground zone. At a small height above the ground plane, the stabilized diffusion current density is observed and used to evaluate the magnitude of ground level current density. The simulated ground level current density agrees well with that in a reference for both reduced-scale and full-scale models where our values are slightly higher. The simulation with the presence of wind shows the wind effect on the ion current density profile as the position of peak current density shifts and the peak magnitude decreases. Compared with the no wind condition, the ion current also takes a wider area under the HV conductor.