Study On Distribution And Control Of Power Frequency Electric Field Under 500kV EHV Transmission Lines

With the improvement of the living standard and the development of technology, the demand for electric power in every walk of life increases rapidly. In order to meet the need of long-distance and large-capability electricity transmission, the extra-high tension electricity transmission lines are widely used. But at the same time, the technology of electric transmission in electromagnetic environment was given a hard test. And more and more attention has been raised to the pollution of electromagnetic radiation produced by transmission and distribution line. Therefore, how to reduce the electric-field intensity produced by high voltage transmission lines has been a hot issue in the environmental protection and the field of Electromagnetic Compatibility Technology. Based on the theory of electromagnetism, it has calculated the electric field intensity under the extra-high tension electricity transmission lines in this paper. And a program has been written to calculate the electric field intensity as well as to analyze the influential factors of intensity of extra-high tension electricity transmission lines, which include the influence of the height of lead wires and the interphase's distance, the influence of divided conductor number, space length and diameters of the lead wires and the influence of conductor pattern and density of field after shield wires are spanned along the transmission lines. In addition, the intervention of other objects will make the electric field aberrant,especially electric field around the transmission lines nearby the buildings. Two ways are worked out in the paper to calculate the density of the perturbed field,namely the finite-element method and the charge simulation method. And the paper applies the analyzing software of the charge simulation method to calculate the density of the perturbed field. In this paper, a simulation experiment of an actual 500 kV transmission lines between tower ~#3,~#4 has been made to model and analyze the way to reduce the electric field. especially to the transmission lines that are used,it founds that the density of field around the wire lines can be reduced by spanning shield wires along the transmission lines, Which has put into practice. From the table, the comparison of the density before and after adding one shield wire is distinct that the electric-field intensity has sharply reduced. So the feasibility of spanning shield wires along the transmission lines is proved. It also presents the current research on environmental effects caused by electromagnetic field in and out of the country, especially in the respect of electromagnetic compatibility. Finally, it puts forward the countermeasure to mitigate transient electric tip and run.