Research on lightning performance of AC/DC hybrid transmission lines on the same tower

Rapid expansion of power system and the limitation of transmission corridor resources have indispensably promoted the development of AC/DC hybrid transmission lines on the same tower under special situations, especially for ultra-high voltage systems being established in China. A hybrid tower model incorporating a double-circuit AC transmission and a bipolar DC transmission is proposed in the study. The lightning performance of AC/DC hybrid transmission lines is investigated based on electro-magnetic transient program (EMTP) and leader progression model, taking into account the operating voltage of transmission lines as well as the competition of multiple upward leaders. The impact of tower´s height, footing resistance, arrangements of ground wires and ground obliquity on lightning protection performance is also analysed. In accordance with the ± 800 kV bipolar DC and the 500 kV double-circuit AC transmission lines on the same tower, the results show that the back flashover and the shielding failure is relatively serious for a 500 kV AC transmission line, which should be paid more attention to. Finally, several methods that may be used to improve lightning protection performance of the AC/DC hybrid transmission lines are presented, such as reducing the tower´s height, using a negative protection angle and installing additional ground wires.