The Research Of Total Electric Field Under Parallel High/Ultra-high Voltage Direct Current Transmission Lines

With the construction of ultra-high direct current power transmission, more and more unavoidable situation of parallel and cross-cutting line will appear. For now, the field strength distribution of single-circuit HVDC lines, at home and abroad have been carried out more research, but few studies on these issues, and the lack of data to support field trials. Therefore,the existing conclusions can not accurately evaluate the parallel high / ultra-high voltage direct current transmission line field strength to provide technical guidance has use value engineering.This paper investigates the analytic calculation method for the synthesis field strength of DC transmission line based on Deutsch assumption, analytical formula calculation of field intensity suitable for DC transmission lines in parallel is deduced, general computing programs are composed using matlab which applied to any circuit DC circuit synthesis field strength calculation. The calculation of the synthesis field intensity of a practical parallel UHV DC transmission lines is simulated based on the programs mentioned above, and the synthesis field intensity of ground under the parallel line is measured on site. Based on the works above, the measured results are found in conformity with the simulation results which verify the practicability and accuracy of the algorithm and programs. Analysis of parallel high/ ultra-high voltage direct current transmission line synthesis field with different poles arranged mode, different lines spacing, different lines heights, different voltage levels and different ways to run. The results showed that due to the mutual influence of positive and negative ions flow space, the field distribution of two paralleled HVDC lines has a larger relationship with the conductor arrangement. When the two-circuit lines have the same polarity, the regional field strength between the parallel increase over a single return line, the inside of the opposite polarity, the area between the parallel lines back to reduce the field strength than single. Meanwhile, with decreasing distance between the two back lines, or line height increases, compared with single-circuit line in the middle region of the resultant field strength increases or decreases the magnitude of the increase, but the two lines outside of the loop field strength and single back line is basically the same. Different voltage levels parallel lines parallel lines with the same voltage level ground synthetic field distribution mainly differ in symmetry, but the overall law basically unchanged. And in the vicinity of the existing DC line corridor when the new addition of a DC line, The minimum height of the line on the ground should be "+o-o" on the ground synthetic field accounting which to meet the currentstandard field strength limits.