Hybrid voltage transmission on the same tower has great advantages and development prospects in terms of increasing transmission capacity

saving line corridor resources and reducing construction costs.In recent years

it is found in the preliminary research on UHV and EHV transmission on the same tower that electromagnetic coupling exists between multiple circuits transmission lines

which affects the overvoltage level of the transmission lines.Therefore

it is necessary to re-evaluate the lightning protection level of extra-high voltage and ultra-high voltage hybrid voltage transmission lines so to ensure transmission safety.In this paper

the single-circuit ±800 kV DC and double-circuit 500 kV AC transmission lines on the same tower are taken as a research object.The ATP-EMTP software is used to set up a distributed parameter model of the line.The simulation models for lightning current

towers and wave（surge）impedance are set up separately.The characteristics of induced over-voltage generated on overhead lines

in case of counterattack and winding

are analyzed.The results show that

in the case of the tower is struck by lightning

the overvoltage on phase A of the AC line is the largest.The measures such as strengthening line insulation and reducing the grounding resistance of the tower can effectively reduce the line overvoltage and prevent the insulation flashover due to lightning strike on the top of tower.In case lightning strike of DC line

the overvoltage of its positive wire is the largest.While

in case of lightning strike of AC line

the overvoltage of phase A is maximum.It provides theoretical basis for such measures as rationally setting up lightning conductors

installing lightning rods

increasing the cross-arm length of the lightning conductors

reducing the protection angle and protecting the positive wire and overvoltage of phase A etc..