Lightning strike is the main cause of transmission line tripping

so it is necessary to investigate lightning impulse responses of transmission line and grounding conductor. In this paper

a lightning impulse model of the free-standing tower of 500 kV double circuit transmission line is established with the software CDEGS

and the lightning impulse responses of the tower and the grounding conductor are analyzed for different lightning current waveforms

tower parameters

soil resistivity

and grounding conductor lengths. The results show that: 1)When lightning strike is on tower top

the current in lightning conductor is proportional to the soil resistivity

and too large lightning current may lead to a breakdown in insulator; 2)Higher impulse voltage peaks on the tower top and the grounding conductor result from shorter wave front time of lightning

narrower width of cross arm

higher height of tower

greater soil resistance

or shorter length of grounding conductor; and 3)In the areas with high soil resistivity

the potential of tower top and grounding conductor can be effectively reduced through extending the length of grounding conductor and lowering soil resistivity.