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.