Study on the Effect of Soil Pore Curvature on Ions Electromigration

The performance of the power system grounding part is determined by the soil impedance characteristic, and the migration of ions in the soil pore water under the influence of an electric field is the main reason for deciding the soil impedance characteristic. The characteristic of porous medium in soil determines the diversity of soil pore curvature and provides migration paths with different curvatures for the migration of ions in pore water. Thus, consistent with the actual soil tortuosity, to study ions electromigration using finite element analysis software COMSOL established four soil pore channels with different radii of curvature. The models assume ions electromigration is not affected by the pore wall and ensure that the same type of ions in the pores, constant temperature, pores size and the length of pore channels are same. According to the simulation calculation, the ion electromigration changes in the pores with different curvature under the same applied electric field. When the soil pores have curvature, the migration speed of the electric field term of the ions on the inside of the curvature is faster than these on the outside, and the migration speed of the pressure term of the ions on the inside of the curvature is greater than these on the outside. The distribution of ions concentration tends to expand outwards with the action of continuous voltage, and the pore with smaller the radius of curvature has the wider the distribution of ions concentration. Based on the analysis of relevant theories, it is concluded that the phenomenon is mainly caused by the applied electric field forming different field intensities in each region of the pore. Moreover, due to the different radius of pore curvature, the pressure inside the pore will change, and the ions with the same initial concentration distribution will migrate in the pores of different radius of curvature and form different local electric fields to affect ions electromigration. Above is the main factor that soil pore curvature affects ions electromigration.