同塔四回输电线路随着线路回数的增加，铁塔高度和横担宽度较单回线增加明显，杆塔塔型对线路的耐雷水平有较大的影响。为了正确评估500 kV同塔四回线路横塔和竖塔的耐雷水平，采用改进电气几何模型（electric geometry method，EGM）与电磁暂态程序（elector-magnetic transient program，EMTP），对比了2种杆塔在不同的地面倾角以及杆塔接地电阻下的耐雷性能，对三避雷线与单耦合地线的防雷效果进行了研究。计算结果表明，横塔的耐雷性能明显优于竖塔，建议在雷害严重地区或是山区采用横塔，在线路走廊紧张地区采用竖塔。

With the increment of circuit number in the transmission lines with four-circuit on a tower, the height and width of tower would increase obviously, which could largely influence the lightning withstand performance of the line. In order to accurately assess the lightning withstand performance of both horizontal and vertical tower, the improved electric geometry method(EGM)model and elector-magnetic transient program (EMTP)are applied to calculate the lightning withstand performance of the two tower type under different ground dip angel and grounding resistance. The results show that the lightning performance of horizontal tower is much better than the vertical one. Therefore, it is highly recommended that horizontal tower be applied in mountain area or serious lightning area, while the vertical tower be applied in the area where the line corridor is scarce.