Study On Power Frequency Electric Field Of The EHV Transmission Lines Based On Boundary Element Method

In our country, electric quantity demanded was continual increase due to the standing rise in country economy. According as the layout by STATE GRID, basis of the extra-high voltage transmission lines UHV transmission lines would be developed in late years. In the building project of extra-high voltage transmission lines, environmental protection stands were increasingly strict to base build.It is a very complicated job to evaluate whether the effect of a transmission line exceeds the standard and tackle. The basis of exact evaluation is to precisely calculate the electromagnetic field produced by the transmission lines. Earth's engaging problem by transmission passage was increasingly austere. Therefore, simulation and analysis to electromagnetic environment of extra-high voltage transmission lines were imperative under the situation.Against the larger equivalent radius of split-phase conductor, boundary element method was used in the paper to analyze the power frequency electric field strength under the transmission lines. Based on Green Theorem, the basic idea of boundary element method was introduced, and the application of the idea of boundary element method in calculating power frequency electric field strength of transmission lines was expatiated in the paper.To more easily simulate, some assumptions about transmission lines are made.The paper researched the simulation of power frequency electric field strength of EHV transmission lines by boundary element method. Main work included the following several aspects:â‘ Planar electric field calculating model was build against EHV transmission line. Then boundary element method and simulate charge method were separately used to simulate. The two calculate results were compared and checkout with actual metrical result. The result showed that boundary element method was feasible in calculating power frequency electric field strength of transmission lines.â‘¡On the basis of modeling the split wires of EHV transmission lines, calculation and analysis of electric field strength against several influencing factors were carried through separately, including height of lines, distance between phases, bundle spacing, numbers of split wires. Then the distributing rules of those factors'influence on EHV electric field strength were summed up, and measures for decreasing its electric field strength were brought forward in the paper.â‘¢To the problem of UHV transmission line, calculating of UHV electric field strength in condition of split wires was carried out. The electric field strength (around split wires and at 1.5m distance to the ground under lines) of 4 different types of transmission line models which were single paraller arrangement circuit, double-circuit on same tower, compact type and single-cup shape, was calculated with out considering the corona around lines. The results indicated that different conductor distributing models could be applied to adapt different geographical conditions of our country. In these models, the compact transmission has the advantages of effectively improving line electromagnetic environment and substantially reducing the transmission corridor width. That could be a kind of reference to choosing transmission line passages.