Investigation Of Lightning Protection Performance Of Yun-Guang ±800kV UHV DC Transmission Line

Long term operation statistical results showed that trip accident due to lightning striking form a big share of all transmission line accidents. So, research of lightning protection performance of UHV transmission line is one of essential subjects especially for the coming construction of UHV transmission lines in china. Therefore, it has important scientific significance and engineering practical value to carry out lightning protection calculation about the UHV transmission line. This thesis discussed the back strike protection performance and lightning shielding performance of the±800kV Yun-Guang UHV transmission line systematically.The leader progression flashover model of insulators and multi-wave impedance model of towers are built based on investigation results of discharge mechanics of insulators and lightning impulse response tests results of towers separately. The ATP-EMTP simulation model used for investigating back strike flashover of UHV transmission line is built, which considers the nonlinear characteristics of ground resistance while lightning impulse current through it.According to the similarity between the lightning discharge and the large gap discharges at the last stage, a new lightning shielding model based on the leader progression is built. The randomicity of progress path of descending lightning leader is applied in the model to research the lightning shielding performance of UHV transmission line, as well as considers the effect of the operation voltage and the ground gradient on the creation, development and final jump of the ascending leader. Compared the electric geometry model (EGM), the computation results of the model in this paper is higher, but it is more access operation results of transmission line. The model in this paper represents the physical process of lightning discharge.The back strike protection performance and lightning shielding performance of the Yun-Guang±800kV UHV transmission line are discussed. The results indicate that the back strike protection performance is so perfect that the probability of back flashover accident is low, with the decrease of ground resistance, the decrease of tower's height and the reinforcement of insulation level, the back strike protection performance is enhanced. The influence of tower height on the back strike protection performance is obviously, the probability of back flashover accident is quite higher, while the height of tower up to 80m.The lightning shielding performance is reduce with the adding of shielding angle, the steepening of ground gradient, and the increase of tower's height. Negative shielding angel should be adopted on the Yun-Guang±800kV UHV transmission line. The shielding angel should be -5°, when the tower's height does not exceed 60m and ground gradient is less than 30°. The shielding angel should be -10°, when the tower's height exceeds 60m and ground gradient is more than 30°.