Simulated analysis of lightning shielding failure performance of UHVAC transmission lines

Accurately assessing the shielding performance of ultra high voltage(UHV) transmission lines has a great reference value for design and construction of lines. We introduced a method for analyzing the shielding failure rate(SFR) of UHV transmission lines based on leader progression model(LPM) and three-dimensional dividing of shielding failure region, in which the actual arc sags and heights from local ground of transmission and grounding conductors in the areas were divided into any scale. To verify the method, the shielding failure trip rate(SFTR) of the 1000 kV UHVAC demonstration line in China and its relation to shielding angel and slope gradient were calculated. Conclusions can be drawn as follows: the SFTR of the ZMP2 and ZBS2 towers in typical plain and mountainous terrain are 0.0575 times/(100 km·a) and 0.0322 times/(100 km·a), respectively, which are acceptable for safe operation of UHV transmission lines in China; the SFTR can be lowered by adjusting sags of the conductors; the conductors at outside of the mountain slope is easier to be struck, and the SFTR increases with shielding angle and slope gradient; the shielding failure under large current occurs far away from the lines.