Conductor Surface Conditions Effects on the Ion-Flow Field of Long-Term Operating Conductors of the HVDC Transmission Line

The influence of conductor surface conditions of new and aged conductors on ground-level resultant electric field and ion current density is analyzed in this paper. The surface roughness and morphology of conductors are measured and analyzed by 3-D phase shift Micro-Xam (MicroXAM-3D) and scanning electron microscopy. Calculations are made using the upstream finite-element-finite difference method for the corona cage model to obtain the influence of surface conditions on the ion-flow field, consequently, changing the resulting electric field and ion current density. An indoor corona cage platform is build up to check the impact of surface conditions on the ground-level resultant electric field and ion current density in the laboratory. Considering the aging characteristics of the conductor surface, a typical ±800 kV ultra-high voltage direct current transmission line is analyzed. The calculated results show that compared with the new conductor, the electric field and ion current density of the long-term operation conductors increase very significantly.