Effect of Slope Terrain on the Ground Level Total Electric Field of HVDC Transmission Lines

The ground total electric field is one of the important indexes of the electromagnetic environment of HVDC transmission lines, which needs to be controlled in the design stage of lines. China ‘s HVDC transmission lines are long and the terrain is complex. The change of terrain will affect the distribution of the ground total electric field. At present, the prediction of the ground total electric field under lines generally assumes that the ground below lines is flat, which is obviously different from the actual environment where lines are located. Therefore, it is necessary to study the influence of terrain on the distribution of ground total electric field. The calculation model of HVDC transmission lines across different typical slope terrains are established. The three-dimensional upstream finite element method (UFEM) is improved to make it suitable for the calculation of the ground total electric field when the terrain changes and then used to calculate the ground total electric field of typical slope terrains. Based on the calculation, the influences of slope angle and the size of the rounded corner generated at the junction of the flat and the slope in the stepped slope on the distribution of ground total electric field are analyzed. The results can provide reference for HVDC transmission lines design and electromagnetic environment evaluation.