Study on the field effects under reduced-scale DC/AC hybrid transmission lines

The possibility for DC and AC power lines running parallel to each other, sharing the same right-of-way or even the same tower has been increased in China. In this work, the coupled DC and AC electric field effects are analysed with a reduced-scale model. Improved measuring methods are proposed to obtain both the DC and AC components of the ground level electric field and ion current density. Depressing effects of the AC field on the ground level DC field and of the DC field on the ground level AC field are observed when the applied DC voltage exceeds the onset value. The mechanism of the influences of AC power lines on the nearby DC power lines is analysed with experiments and simulations. Both the influence of the AC field on the corona onset on the surfaces of DC conductors and the influence of the AC field on the motion of the space charges are proved to be important in the field effects under the hybrid lines.