Research on Lightning Performance of Back-flashover of UHV Direct Current Double-circuit Mixed-voltage Transmission Lines on the Same Tower

UHV direct current mixed-voltage transmission lines on the same tower can effectively solve the contradiction between growing power demand and resource shortage of power transmission corridors, thus doing research on the lightning protection performance of the transmission lines is of great significance. Based on EMTP-ATP, this paper presented an intersection method as insulation flashover criterion for insulator flashover simulation process, carried out analysis validation through examples, studied lightning back-flashover performances of two tower models and influencing factors thereof. By making comparison with ±800kV direct current single-circuit lines and ±500kV direct current double-circuit lines, this paper obtained characteristics of lightning protection performances of back-flashover of UHV direct current mixed-voltage transmission lines on the same tower. The results indicate that the 500kV lines are the weakness of back-flashover of the UHV direct current mixed-voltage double-circuit transmission lines, which require key protection.