Comparison of corona degree between the stranded and the shaped wires of HVDC transmission lines

Most of high voltage transmission lines use the stranded wire, while the surface of the shaped wire is smoother than the stranded one. It is investigated in this paper that how much the corona can be weakened by the shaped wire, by calculating the ion flow. The steady state corona model is employed, and a local domain surrounding the wire is chosen as the field domain to simulate the corona phenomena near the wire precisely. The equation system of corona model is a multi-physics coupled problem with electric field and particle diffusion and migration. The approach of defining and applying the boundary conditions for negative and positive wires is proposed, and the solution of coupled problem is implemented by using software COMSOL. By the simulation of 500 kV transmission line, the corona current of the shaped wire is around 35% less than that of the stranded wire.