Research Of Calculation And Prevention Of Lightning Induced Overvoltages On Overhead Distribution Lines

The most part of the overhead distribution lines are exposed in the air,so they are apt to be damaged by lightning and cause lightning overvoltages,which will interrupt power supply and affect users' production and lives.For the overhead distribution lines,the damage of direct lightning is worse than induced lightning,so the research of the overhead distribution lines has mainly focused on direct lightning for long time,and the research of induced lightning is rather less.Researches indicate that the main factor of 10kV overhead distribution lines' flashover or faults by lightning is induced lightning instead of direct lightning,the proportion of the faults by induced lightning exceeds 90%.Therefore, it's significant to research the calculation and prevention of lightning induced overvoltages on overhead distribution lines.There are many articles on the calculation of lightning induced overvoltages on overhead distribution lines,but the ground is considered as a perfect conductor in most articles of China.This thesis researches the calculation model of the lightning induced overvoltages on overhead distribution lines by nearby lightning while the ground is considered as a perfect conductor and an unperfectly conductor,then applies electromagnetic transient emulator programme ATPDraw to validates the calculation model of the lightning induced overvoltages on overhead distribution lines.The result indicates that the calculation model of the lightning induced overvoltages on overhead distribution lines researched in this thesis is adapt to calculate the lightning induced overvoltages on overhead distribution lines.This thesis also researches the factors which affect the amplitudes and the wave shapes of the lightning induced overvoltages on overhead distribution lines,the result indicates that parameters such as the parameters of lightning current,the high of the line,the position of lightning and ground conductivity affect them.Finally,from the angle of reducing lightning induced overvoltages,this thesis does research on the calculation of lightning induced overvoltages on overhead distribution lines when coupling lines are installed.Then this thesis analyzes the installed position of a coupling line in 10 kV overhead lines when the lines are arrayed in triangle or in one line,the result indicates that when the coupling line is installed among phase lines the lightning induced overvoltage is reduced more. This thesis calculates the best installed position of a coupling line in 10 kV overhead lines when the lines are arrayed in triangle or in one line.The research of this thesis is of instructional significance to prevent the overhead distribution lines from lightning.