Study on the hybrid ion-flow field of HVDC and HVAC transmission lines by the nodal discontinuous Galerkin time-domain method

The high-voltage direct current (HVDC) and HV alternating current (HVAC) hybrid transmission lines in the same corridor is an effective way to enhance the power transmission capacity of the corridor and save land resource. The transmission lines parameters such as the corridor width, the height of transmission lines, and electromagnetic environment can be analysed and optimised by the calculation of the hybrid ion-flow field. In this study, nodal discontinuous Galerkin time-domain method is for the first time applied to the calculation of the hybrid ion-flow field. Furthermore, corona interactions between the HVDC and HVAC lines are considered in the process of numerical solution. Compared with measured results and previous methods, the proposed approach is verified to be able to obtain wiggle-free numerical solution with significantly reducing the computational burden, and meanwhile, the calculation precision is increased greatly. The ground-level electric field and ion current density of the hybrid lines in time domain are analysed, and then the time-domain characteristic is explored. Finally, the ion-flow fields of the hybrid ±800 kV DC/500 kV AC transmission lines in parallel and on the same tower have been made a comparative analysis and optimisation, which provide theoretical basis for real hybrid towers design.