Ion Current Density for a Bipolar HVDC Transmission Line Analysed by Numerical Simulations

Abstract:
According to an existing standard (E DIN IEC/TR 62681 VDE 0210-99:2018-07), the electric field and the occurring ion current density at a bipolar high voltage direct current (HVDC) transmission line system can be approximated by the superposition of two monopolar HVDC transmission line systems. In order to investigate this approximation in more detail, a new method is used, which was presented and validated in a previous publication. With the help of this new approach, the ion current density (sometimes also called corona current density in literature) resulting from the corona discharge, the electric field strength and the space-charged potential field can be calculated numerically. The unknown space charge density on the conductor surface is not determined by iterative methods, but directly with Lagrange multipliers. For this purpose, the space charge density is divided into a constant and a space-dependent component. Finally, the new approach is used to analyze and compare the fully coupled bipolar model and the superimposed monopolar model.