Under the condition of the single-polar operation, the current that flows into the earth through the DC electrode will cause distortion in earth surface potential (ESP), and have adverse impact on the surrounding environment and AC power grid. In this paper, firstly, the distributions of ESP of both typical and multi-layer soil models are calculated and analyzed by finite element method (FEM). The influences of the current magnitude, the distribution of soil resistivity and the specific size of the ground electrode on the distribution of ESP are taken into account. Secondly, considering AC power transmission lines, transformers and other components, a DC equivalent model of the network is established. Finally, the DC bias current of the network is calculated on basis of the grid and soil models, which provides a reference for prevention and management of the DC bias current.

bias current,earth surface potential (ESP),finite element method (FEM),ground electrode,multi-scale model