The corona discharge of HVDC transmission lines can generate ion flow field. The surface roughness of HVDC transmission line increases because of the sand blown by the wind and friction

which leads to the decrease of the corona initial voltage. Therefore

the surface micro-geometry of a transmission line has a direct effect on the ion flow field.In this paper

wire samples with different roughness were treated with sand particles to simulate the influence of sand blown by wind on transmission lines. Based on the light sectioning

the micro morphology of surface of a wire sample was analyzed

and the roughness of wire samples was obtained. The electric field of wire surface with different surface micro geometry was calculated by FEM. When the roughness increases

the maximum electric field of the wire surface will increase

and the number of spiked protrusions will increase. Moreover

the initial voltage of corona of a wire sample was measured by a corona cage method. The correlation between surface roughness of wire and roughness coefficient in Peek formula was established. As the roughness increases

the roughness factor will decrease. The correlation is applied to the ion flow field calculation. Furthermore

the roughness coefficient was characterized by the measured surface roughness to ensure the expression of the micro-geometry of the wire surface more reliable.