| The erection for two circuit DC transmission lines in the same corridor can increase the power transmission capability of the unit corridor, however, there still have been no engineering application precedents in the world for the construction of two circuit DC transmission lines in the same corridor. The situation of parallel adjacent erection for Jinping-Sunan and Xiangjiaba-Shanghai±800kV DC transmission lines will appear in some sections in China, and the method studied to predict the total electric field at the ground level under this type of lines can provide theoretical references for engineering design and electromagnetic environment protection.In this paper a method for calculating the total electric field at the ground level under two circuit DC transmission lines in the same corridor based on the Upstream FEM Method was studied. Distribution laws of the total electric field at the ground level under this type of lines were gained by test results, and the calculation method was proved also. Finally the total electric field at the ground level of Jinping-Sunan and Xiangjiaba-Shanghai±800kV DC transmission lines in the same corridor was calculated with practical engineering application and its influencing laws of changes of the separation distance of two circuit DC transmission lines in the same corridor, the height of transmission lines, the inter-electrode distance and wind velocity were studied.(1) A calculation method for the total electric field at the ground level under two circuit DC transmission lines in the same corridor was proposed which is based on the Upstream FEM Method, and this method can consider the difference between corona onset electric field strengths of the positive and negative poles, and the difference in types of conductor bundles, height of every pole, separation distance of two circuit DC transmission lines, inter-electrode distance and pole arrangement scheme.(2) The total electric fields at the ground level under two circuit DC analog line sections in the same corridor are tested. The validity of calculation method was proved by test results. The results of calculation and test were obtained and shown as follows. The different pole arrangement schemes of two circuit DC transmission lines in the same corridor would not notably influence the magnitude of the maximum total electric field at the ground level, but would influence its distribution location. The absolute value of the maximum total electric field at the ground level under two circuit DC transmission lines in the same corridor is not greatly different from that of just one circuit in normal operation.(3) With practical engineering application, the total electric field at the ground level of Jinping-Sunan and Xiangjiaba-Shanghai±800kV DC transmission lines in the same corridor was calculated on the condition of the different pole arrangement schemes and structural parameters. The results were shown as follows. With the increase of the separation distance of two circuit DC transmission lines in the same corridor, the magnitude of the maximum total electric field at the ground level would not be notably influenced, but its distribution location would be influenced. With the increase of the height of transmission lines, the maximum total electric field at the ground level would notably decrease. Changes of the inter-electrode distance for different pole arrangement schemes would not notably influence the maximum total electric field at the ground level and its distribution location. With the increase of wind velocity, the maximum total electric field at the ground level would notably decrease and its distribution location would skew before the wind. The magnitude of the maximum total electric field at the ground level under this type of lines with one pole tripped off would not be notably influenced. |
