Analysis of monitoring effect on Hybrid Electric Field for AC/DC Cross Line

Electrostatic induction charge which generated by the coupling effect of hybrid electric field of AC/DC cross line and metal object under the transmission line can cause different levels of electric shock injury to human. In order to find out the distribution law of the hybrid electric field and reduce the effect of electrostatic induction, this paper set up shielding lines which paralleled to the AC and DC lines respectively on the outside of the side conductors and along the diagonal of parallelogram at crossing point, then measured the electric field distribution in shielding areas of 750kV AC and 500kV DC lines and the induced voltages of shielding lines in different states, analyzed the effect of shielding line on power frequency electric field and DC composite electric field. The results showed that shielding lines have a reducing effect on the hybrid electric field of the cross lines, the average power frequency field strength is reduced by 12.6%, the DC composite field and power frequency electric field at the crossing position was far less than the limits specified in the respective standards. Both induced voltage of bare lines and shielding lines wrapped with adhesive tape increase with the raise of erection height. Under the same conditions, the average induction voltage of bare conductor is 9.3% higher than that of shielding lines wrapped with adhesive tape. There is no obvious difference between parallel and vertical erection methods of the same number of shielding lines in the degree of reduction of induced voltage.