中文摘要：

为评估、计算输电线路雷电屏蔽性能即绕击性能，基于长空气间隙放电理论建立了特高压直流输电线路雷电屏蔽的先导发展模型，并用该模型计算了拟建立的云广±800kV直流特高压输电线路雷电屏蔽性能。计算结果表明：随着地面倾角、保护角的增加，线路屏蔽失效率明显增加，特高压直流输电线路最好采用负保护角运行。

英文摘要：

According to the operation data abroad, the tripped--out accidents caused by shielding failure amount to a large percentage of the tripped--out accidents caused by lightning strike on the UHV AC transmission lines. Based on the discharge theories of long air gap, a leader propagation model on lightning shielding failure is presented in this paper. The leader propagation process and the selection of the lightning striking point are assumed to be related with the＇space electric field distribution around the transmission lines in this model. The initiation of the upward leader from the transmission lines and the final jump between the upward and downward leaders are determined respectively by the electric field calculation on the transmission lines and the air gap between the upward and downward leaders. Based on this model, a calculation program on the estimation of lightning shielding performance of transmission lines is built in this paper. With this program, the lightning shielding performance of Yun--Guang ± 800kV UHV DC transmission lines to be constructed is calculated. The results indicate that the shielding failure radio will increase with the increment of the slope angle and the shielding angle. Therefore, the negative shielding angle is suggested to be adopted in UHV DC transmission lines.