Research on Electromagnetic Induction and Grounding Switch Selection of AC / DC Mixed Voltage Transmission Lines on the Same Tower

With the continuous growth of power transmission demand, the problem of resource shortage in transmission corridors is becoming more and more prominent. In order to improve the utilization efficiency of transmission corridors, the construction of AC / DC co-tower projects will become an important development direction. Taking the erection of a ± 800kV DC line and a 500kV AC line on the same tower as an example, this paper analyzes and calculates the influencing factors of electromagnetic induction, and then analyzes the suppression effect of AC line transposition on electromagnetic induction. It is found that when the transposition tower is at the midpoint of the same tower erection section, the suppression effect is the best, and a variety of transposition schemes are comprehensively compared. The results show that the electromagnetic induction suppression effect is the best when the two upper transposition methods are adopted and the first section of the tower is arranged in reverse sequence, which is about $75 \%$ lower than that without transposition. Finally, the selection and analysis of the DC line grounding switch are carried out.