Research Of Lightning Induced Overvoltage On Overhead Lines

The overhead distribution lines are exposed in the air, so they are apt to be damaged by lightning and cause lightning overvoltage. The overvoltage may causes line protection device break or even causes circuit electrical equipment damage, 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 35kV and lower overvoltage levels 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 overvoltage on overhead distribution lines.This paper analyzes the production principle of lightning induced overvoltage and researches a variety of theories and methods about induced overvoltage calculation at home and abroad. It studies overvoltage which might appear on overhead lines when lightning strikes towers from different angles. This article analyzes of the physical process in detailed used Maxwell's electromagnetic field theory when lightning strikes tower. Then it researches the main factors that impact the induced overvoltage simply, such as tower parameters and the length of the uplink leader.This thesis also researches the factors which affect the amplitudes and the wave shapes of the lightning induced overvoltage 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. According to the theoretical analysis of generation process of induced overvoltage and parameter model used in simulation, this paper builds appropriate circuit parameter model and lightning current model. Then it simulates and analyzes the process of lightning strikes towers used PSCAD (Power System Computer Aided Design) in order to improve the lighting resisting level. In the simulation, it primarily simulates the following circumstances: there is no protection measures, enhance the line insulation and install overhead ground wire and arrestors with different grounding resistance. Though the simulation results and monitoring in field, it obtains the measures of improve the lighting resisting level of lines. The research of this thesis is of instructional significance to prevent the overhead distribution lines from lightning.