Effect of backfill soil impurity on electric field characteristics of HVDC grounding-electrode

To study the effect of impurities on performance of HVDC common grounding electrode, this paper establishes the model of grounding current field using COMSOL software, and analysis the effect of gravels and voids in backfill soil. The research results show that, these impurities will affect the distribution of the electric field intensity around the grounding electrode, and the most obvious influence is on the maximum electric field intensity of coke surface. When the radius of gravel and void is close to the grounding-electrode´s radius, the depth of the impurities is about 1.6 meter and the position is above coke´s section 1/4 respectively, the maximum electric field intensity on the surface of coke reaches minimum. Although the presence of impurities makes the maximum electric field intensity of coke surface exceed its control value, in some cases the value is smaller than that without impurities, which can be used to reduce the maximum value. The result has a certain reference and guiding significance on construction quality control of other grounding electrode.