Simplified calculation of maximum ground‐level electric field when two HVDC transmission lines run across at any intersection angle

When two HVDC transmission lines run across, because of the interaction between the two lines, the maximum ground-level total electric field is not a simple superposition of the maximum ground-level total electric field generated when the two lines exist alone. This paper presents an approximate method to use the maximum ground-level total electric field when only the lower line exists as the maximum ground-level total electric field when two lines run across. Here, the 3D method of characteristics has been improved to make it suitable for structure of two lines intersected at an angle using a method of coordinate transformation. The 3D method of characteristics is used to calculate the theoretical maximum electric field when the two lines run across. The 2D FEM is used to calculate the approximate maximum electric field when only the lower line exists. The approximate results and theoretical results are compared for line structures of ±800 kV line runs across ±800 kV line, ±660 kV line, and ±500 kV line at any intersection angle. The approximate errors are < ±10%, which can meet the engineering requirement.