A Time-Domain Approach of Ion Flow Field Around AC–DC Hybrid Transmission Lines Based on Method of Characteristics

The nonlinear ion flow field around ac-dc hybrid transmission lines due to corona varies with time. As the electric field and the space ions interact with each other, iterative algorithms, which include electric field calculation and ion density calculation, are usually used to simulate the ion flow field. In this paper, based on a pair of first-order partial differential equations of the ion densities, a time-domain method of characteristics is presented to calculate the ion densities analytically. Then, a time-domain iterative approach with the help of the method of characteristics is developed to calculate the ion flow field around ac-dc hybrid transmission lines. Because the electric field is also calculated analytically by accumulating all the contributions from the ions in the space and the charges on the surfaces of the conductors, almost all variables can be obtained via analytical formulas and no large-scale system of equations needs to be solved. The calculated results are in good agreement with the measured ones.