Lightning protection on the large crossing section of single circuit ±800kV UHVDC and double circuit of 500kV transmission lines erected on the same tower

For ±800kV UHVDC project, due to the limitation of corridor, some sections need ±800kV and 500kV AC lines to be erected on the same tower. When at the large crossing section ±800kV DC transmission line and 500kV line are on the same tower, the height of the tower is further increased, and the lightning area is increased, so it is important to research the lightning protection and adopt proper lighting protection measures. In this paper, the lightning protection scheme is determined by the criteria that the safe operation years of large crossing section of UHVDC project under lightning overvoltage shall not be less than 50 years. Based on Chizhou large crossing section that is erected in the mode of UHVDC and EHVAC transmission lines on the same tower of the UHVDC project from Baihetan to Jiangshu, the lightning shielding failure outage rate and back flashover outage rate were given, and the flashover outage rate while lightning stroke on the grounding wire in the middle of the large crossing section. Based on the results of the lightning overvoltage calculated above, the lightning protection measures were proposed.