Research On Induced Lightning Overvoltage Calculation And Protection Technology Of Overhead Distribution Lines

The overhead distribution lines are an important part of power transmission and distribution and have an important position in the power system.With the development of China's power system,its grid structure is becoming more and more complex.Due to the low level of insulation,as the system capacity increases,the system is prone to accidents in the event of a lightning strike.If it is not handling properly,it may directly lead to the collapse of the power grid,which will bring immeasurable losses to people's production and life.According to related research,large-scale blackout trip accidents caused by inductive lightning accounted for 90% of lightning strike failure rate compared to direct lightning strike accidents with a probability of less than 20%.In view of the above problems,this paper quantitatively analyzes the induced lightning overvoltage on overhead distribution lines,and studies the lightning protection technology of the line.This is of great significance and practical for improving the lightning protection work of distribution lines,reducing the lightning trip rate and improving the reliability of power supply.This article main research content is as follows:1.This paper introduces the lightning discharge process and the formation mechanism of induced lightning overvoltage.2.The mathematical model of the lightning current(the mathematical model of the six lightning strikeback channels,the four current modes of the lightning channel)and the specific equations,characteristics and applicable scope of the electromagnetic field-transmission line coupling model are combined and compared.The transmission line model(TL model)and the double Heidler function are used to form the lightning current mathematical model.The Agrawal coupling model is the electromagnetic field-transmission line coupling model.3.In this paper,the two-dimensional time domain finite difference algorithm(2-D FDTD)is applied to the electromagnetic field calculation around the overhead distribution line and the inductive lightning overvoltage calculation on the line.After the algorithm is validated,using the algorithm to study the influencing factors of lightning overvoltage induced by distribution lines in the presence of uniform conductivity on horizontal ground.4.Using the 2-D FDTD algorithm,the influence of the upper and lower soil conductivity and the thickness of the upper and lower soil on the induced lightning overvoltage of the distribution line is analyzed for the mountain with dip angle of 0 degree and 45 degree and the conductivity level is layered.5.A comprehensive evaluation model was established using the 9/9-9/1 scale method in the analytic hierarchy process to study the induced overvoltage protection technology for overhead distribution lines.For the overhead distribution lines,the main lightning protection measures are proposed,such as installing lightning arresters,increasing the number of insulators,installing arcguiding insulators,and installing insulated cross-arms.Comprehensive evaluation from the aspects of service life,engineering cost,reduction of lightning strike rate,operation and maintenance,etc.,and the optimal lightning protection transformation measures are obtained,and applied to the actual lightning protection transformation demonstration project,combined with the data of lightning strikes before and after the transformation,the lightning protection effect analysis.