Soil model establishment of UHVDC grounding electrode under complex geological conditions

In recent years, with the large-scale development of long-distance, large-capacity DC projects, the degree and extent of the impact of the ground electrode on the surrounding power facilities cannot be ignored. If it cannot be accurately evaluated during the design phase, it will be detrimental to the safe operation of the power grid and bring additional investment. The accurate soil model is a prerequisite for analyzing the Earth Surface Potential (ESP) distribution and evaluating the effects of DC bias. However, the existing soil model calculation results have large errors, which make the evaluation of the DC bias effect inaccurate. To this end, this paper proposes a non-axisymmetric horizontal-vertical two-way layered composite soil model. Based on the three-dimensional resistivity data, the polar soil is dispersed into several small soil blocks, and the surface potential distribution is calculated by the finite element method. At the same time, in order to solve the problem of the computational increase of the three-dimensional model, the model is simplified according to the calculation principle, so the calculation memory is reduced and the calculation speed is improved while ensuring that the calculation accuracy is not affected.