Calculation of earth surface potential distribution of HVDC due to finite element and multi-layer soil

Strong electric field will be produced in the earth around the grounding poles when HVDC transmission system operates in ground-return mode, which would have effects on the electric power equipments and the underground metal pipes nearby. This paper builds a model of multi-layer soil and a typical soil model on the basis of actual distribution of soil around the grounding poles, and then performs a calculation of earth surface potential distribution of typical soil model by finite element method. A comparison between the two different models is proposed to illustrate the different grounding characteristics of the DC earthed pole and different effects on the distribution of earth surface potential. The results show that, the ground resistance and the step voltage around the site are much affected by the soil resistivity where the grounding locates. While the ESP, which is within the range of tens of meters,is affected by the deep soil resistivity.