To study on the ability to triggered lightning of a overhead transmission line tower head

a typical 500 kV AC transmission line model with a ratio of 1:25 is established.Numerous discharging experiments are conducted with standard switching voltage impulse.With analysis on experimental data

variation of transmission lines shielding failure probability from the tower head to the middle line span is achieved in this paper.The combination of theoretical analysis and on-site operation experiences shows: Tower head’s triggered lightning ability is obvious

but it is limited in protection scope.The combination of operating experience and theory analysis shows that the tower head has obvious triggered lightning ability while its protective range is limited

and transmission line near the tower is of the largest shielding failure probability.The test described in this paper can provide reference to where electrode should be set on during shielding failure simulation tests

but also can indicate a transmission line range that can be easily suffered from shielding failure and needs more protective measures.This can be a guidance to improve more on the safety of transmission line operation.