Lightning Protection Of ±500kV Three-circuit VSC-HVDC Overhead Transmission Lines On The Same Tower

Three-circuit VSC-HVDC Overhead Transmission Lines on the sale tower is beneficial to saving transmission line corridor.But comparing to single or double circuit transmission line,lightning protection design for three-circuit transmission lines is more complicated.The striking flashover rate should be strictly controlled especially in the situation of DC gird structure.Based on the background of Zhangbei ±500kV flexible DC power grid test demonstration project(single circuit),the lightning resistance performance of ±500kV three-circuit flexible DC transmission line on the same tower is studied.The main research work of the thesis is as follows:Firstly,the typical lightning parameters such as ground flash density and lightning current are introduced,and on this basis,the mechanism of lightning overvoltage generation is discussed.For the lightning protection performance analysis of overhead transmission lines,the wave process in parallel multi-conductor transmission lines is used.Discusses the analysis model of lightning counterattack and lightning deflection on the transmission line;It lays the foundation for the subsequent lightning protection analysis of ±500kV three-circuit flexible DC transmission line on the same tower.Secondly,based on the terrain and geomorphology,ground flash density and line parameters of the ±500kV flexible DC power grid test and demonstration project in Zhangbei,an electrical geometric model of±500kV three-circuit flexible DC transmission lines on the same tower was established,the influence of parameters such as conductor layout,tower height,topography and lightning protection angle on the lightning protection performance of three-circuit flexible DC transmission lines on the same tower,and the distribution of the deflection trip rate under different parameters is obtained.Finally,based on the ATP-EMTP simulation software,a counter-attack analysis simulation model of ±500kV three-circuit flexible DC transmission line on the same tower was established,the variation law of the lightning strike resistance level and strike trip rate of the transmission line with the arrangement of the pole conductor,grounding resistance,tower height and other parameters were studied;Analysis of the lightning resistance performance of deflection and counterattack of integrated lines,the layout plan of the pole wire and metal return line of ±500kV three-circuit flexible DC transmission line on the same tower is proposed.The research results laid the foundation for the lightning protection design of the follow-up±500 kV three-circuit.