Model test on the effect of hillside on lightning shielding performance of ±1100 kV transmission lines

Abstract Lightning damage is one of the main causes of faults in transmission lines. To study the effect of terrain on the lightning shielding performance of UHV transmission lines, with negative 250/2500 μs switching impulse voltage, a large-sized model of the Z38102AL tower with the ratio of 1:12.5 for ±1100 kV UHV transmission lines is used to conduct the simulation tests in hillside in this paper. According to the pictures of discharge process, the discharge process of transmission line around the hillside area is analyzed. The results show that the ground potential rise in the hillside area changes the space electric field, and the attraction of the slope to the downward leader makes the transmission lines in the hillside area more vulnerable to lightning. The test results show that the equal probability curve of the shielding failure spatial region is inclined parabola curve, and the shielding effect of the slope is weak, the dispersion of discharge increases, which leads to the decrease of the difference in the attraction ability of the conductor voltage polarity to lightning. By comparing the test results with the plain model test, the results show that distribution of discharge is larger and the total shielding failure probability is higher in hillside area. Conclusively, under the influence of hillside slopes, the increase of exposure space and the change of space electric field caused by the rise of ground potential have a stronger effect on the shielding failure probability than the polarity effect of conductor voltage, which makes the difference of conductor polarity in hillside area smaller. It is found that the influence of voltage polarity of ±1100 kV conductor on the probability of shielding failure is stronger by comparing the results of ±1100 kV test and ±800 kV test.