Calculation of 3-D Ion-Flow Field at the Crossing of HVdc Transmission Lines by Method of Characteristics

In this paper, a 3-D iterative approach is presented to calculate the nonlinear ion-flow field around two cross-over HVdc transmission lines. The electric-field resulting from space charges is calculated by an integral method. An analytical formula to calculate the space charges along the electric-field lines determined by the electric field is derived based on a 3-D method of characteristics. The electric-field distribution and the space-charge distribution are calculated iteratively until a convergence is reached. Since both the electric field and the space charges are mainly calculated by analytical approaches, the approach greatly reduces the computing scale and can be used for 3-D calculation. The approach was validated by the experiment on a reduced-scale model. The ion-flow field at the crossing of two +/- 800-kV transmission lines was calculated with the method and discussed.