Research On High Efficiency Numerical Methods Of Ion Flow Field Of HVDC Transmission Lines And Their Applications

With the HVDC projects rapidly developing in China, the ion flow field (including the total electric field and the ionic current density, etc.) problems of the HVDC lines are more and more prominent. The numerical methods for calculating the ion flow field of the HVDC lines are developed in this paper and some important ion flow field problems are studied deeply. These problems include the ion flow field with the human body under the HVDC lines, the charged effect of the conductor in the ion flow field, the total electric field distribution with the building under the HVDC lines. The research results could lay the foundation for forecasting, controlling and evaluating the electromagnetic environment of the HVDC projects.The upstream finite element method (upstream FEM) for calculating2D ion flow field of the HVDC lines is developed firstly and high efficiency is obtained. Considering the features of the method, three suggestions are proposed for the calculation procedure as follows:(1) in order to obtain accurate electric field on the surface of the conductors, it suggests that the boundary divisions of a single wire should not be less than80and the finite element method with constrained electric field equation on the boundary should be used to calculate the electric field on the surface of the conductor;(2) the direct decomposition method should be adopted to solve the FEM matrix equation;(3) without wind the charge density updating order should be determined by the nodal electric potential order, so that the charge density is updated along the charge movement direction to accelerate the convergence.3D upstream finite element method (3D upstream FEM), a method suitable for calculating bipolar3D ion flow field under the HVDC lines, is proposed. It shows the validity of the method that the numerical results coincide with the analytic solutions and the measurement results. The numerical method coupled of Galerkin FEM and Newton method is developed to analyze unipolar ion flow field. A new scheme for calculating3D ion flow field is proposed and it significantly reduces the memory requirements and the matrix equation solution cost.A numerical method is proposed to calculate the electric potential of the conductor grounded with a resistance in the ion flow field of the HVDC lines. It shows the validity of the method that the numerical results coincide with the measurement results. Considering±800kV HVDC lines, the lines of one pole run at the normal state and the lines of the other pole are electric-potential-floating and standby. Then the electric potential of the standby lines is calculated by using the above method. The distribution features of the total electric field with the building under the HVDC lines are also analyzed.By using the proposed3D numerical method, the ion flow field with human body under the HVDC lines is analyzed. A human body model suitable for3D ion flow field analysis is built up. The total electric field and ionic current density distribution is analyzed as the human body model grounded directly and grounded with a resistance. The features of the total electric field and the charged effect of the ionic current with human body under the HVDC lines are obtained. It could provide important reference for evaluating the electromagnetic environment with human body under the HVDC lines.