Shielding effect of ac conductors in ac/dc hybrid power transmission

The increasing requirement for the power transfer capability has raised the possibility of dc transmission lines operating on an existing ac transmission corridor. Corona effects in such hybrid ac/dc lines become much more complicated due to the interaction between the ac and dc fields. This thesis presents a method to investigate the ionized field of such hybrid ac/dc lines and evaluate the shielding effect of the ac conductors on the electric field intensity and the ionic dc current density at ground level from the point of view of environmental impact. The method is based on an iterative finite element procedure to solve the time invariant ionized field.;A comparison between the calculated and experimental results for a laboratory line is presented. The calculated values of the current density at ground level agree satisfactorily with the experimental results.;The calculated data, including the ground level lateral profiles of the electric field intensity and the current density for practical hybrid transmission line configurations, are also given in this thesis. For further discussion of the shielding effect of the ac conductors on the electric environment in the hybrid ac/dc lines, the calculated data for a bipolar dc transmission line configuration are presented as well. The results show that with a proper ac line arrangement, the hybrid ac/dc line geometries have the advantage of reducing the ionized field and the current density at ground level.