Numerical Simulation Of Plasma Field Around Excessive High Voltage Transmission Lines

Ground level total electric field strength(TEFS) and ion current density(ICD) are primary parameters influencing the electromagnetic environment of a high volt direct current(HVDC) line and deciding the clearance-to-ground of the line. Methods for calculation of TEFS and ICD can approximately be classified to three kinds: Deutsch Presumption Method(DPM),Half Empirical Method(HEM) and Finite Element Method(FEM).DPM presumes that the presence of space charges only changes the magnitude of the TEFS and doesn't change the direction, thus simplifies the calculation from two dimensions to one dimension. HEM is a method obtained from the synthesizing of theoretical analysis and measurements under HVDC lines. FEM is a method of numerical calculation and has advantages in dealing with non-linear problems and problems with complicated boundaries.The paper calculates the total electric field strength and plasma density of direct current transmission line with the upstream finite element method.Mathematical expression equations and boundary conditions namely mathematical model are derived based on the theoretical analysis of ionized field. Upstream Finite Element Method was introduced into solution process to solve the non-convergence problem in iterative process and made the iterative process finish more fast; Then the mathematical model was solved with FEM; Finally related simulation program was compiled with Visual Basic+SP6.The validity of this method is verified by the contrast between the analytical solution of coaxial cylindrical structure and the actual measurements.Because HVDC transmission has been widely used, and more experience has been accumulated in engineering construction. In order to contrast, strength and distribution of Electric Field Strength of HVDC transmission is discussed in this paper. The results showed that the height of wire influences the synthetic field significantly, the wire-to-ground is higher, the synthetic field is smaller; and the interelectrode distance has a relatively small influence on the synthetic field, the interelectrode distance is greater, the synthetic field is smaller.At last this paper calculates the TEFS of four conductor plans of the reforming Gezhouba-Shanghai HVDC transmission lines. And the best plan is recommended. It can provide design reference dates for practical DC line.