Obtained by emtp program and the egm , this paper studies on lightning protection performance on 500kv double circuit transmission line the distributed parameter model of tower is built when analyzing the back stroking lightning protection performance for double circuit line , it can truly reflect the spreading course of lightning current on the tower , furthermore , considering the randomness of working voltage ' s phase when lightning strokes the top tower and supposing the probability of lightning appearing arbitrary phase in a cycle of ac is equal , this paper brings forward the statistical method to calculate the rate of back stroking on double circuit line 本文利用emtp程序、擊距法對500kv同桿雙回線路的耐雷性能進行了研究。在分析同桿雙回線路的反擊耐雷性能時,建立了桿塔的分布參數(shù)計算模型,此模型可以真實地反映雷電流在桿塔上的傳播過程。并針對雷擊塔頂時,導(dǎo)線運行電壓相位角的隨機性,本文假定雷擊出現(xiàn)于交流一周期的任一角度區(qū)間內(nèi)的概率相等,提出了利用統(tǒng)計法計算同桿雙回線路的反擊跳閘率。