| Most of the fault trips of transmission lines are caused by external force or natural disasters.For 35 kV Transmission lines,the problem of fault trips caused by induced lightning overvoltage is the most prominent.Limited by the frequent impact of mined areas,the 35 kV Transmission Line in Shaoguan area is facing a lot of lightning damage test.Due to the number of old lines,the early design considerations are not comprehensive,resulting in a lot of pressure on equipment operation and maintenance.In order to reduce the trip rate of the line,control the risk of voltage loss of single power substation,relieve the load transfer pressure of the distribution network,guarantee the power supply of villages and towns,and improve the satisfaction,it is the key to do a good job in the lightning protection of 35 kV Transmission line.Based on the research and analysis of the calculation method of lightning induced over-voltage of transmission lines,the mathematical model of the research object is established,and the main factors that will affect the induced over-voltage of overhead transmission lines are described.Based on the lightning activity and the practical effect of lightning protection in Shaoguan area,the lightning protection effect is analyzed and the improvement strategy of lightning protection measures for 35 kV Transmission Lines in the area is proposed The research contents include:1)describe the basic knowledge of line induced lightning overvoltage and the significance of studying induced lightning overvoltage.This thesis expounds the current situation and existing problems of the research,and analyzes and summarizes the calculation methods of induced lightning overvoltage.2)the process of lightning generation and thundercloud discharge is described,and the formation,characteristics and physical structure of thundercloud are introduced.3)the calculation method of electromagnetic field around lightning channel is introduced.Two kinds of field line coupling models,Taylor model and Agrawal model,are described respectively.Through two different considerations of the influence of the earth conductivity,the electromagnetic field in the corresponding case is obtained.Select the best model to complete the calculation of induced lightning overvoltage.Finally,considering the engineering practice and the main factors affecting the induced lightning overvoltage,the simplified model is applied and analyzed.4)Collect the operation data of transmission lines in Shaoguan area,analyze the current lightning protection situation of 35 kV Transmission lines,identify the causes offrequent lightning trips,through the application of actual lightning protection measures for transmission lines in mountainous areas,analyze the effect of lightning protection and the areas to be improved,and finally put forward optimization suggestions for lightning protection measures for 35 kV Transmission Lines in mountainous areas.Through the theoretical elaboration and calculation analysis of induced lightning overvoltage,it is considered to strengthen the line lightning withstand level to carry out induced overvoltage protection.According to the current situation of 35 kV Longjiang line lightning protection,in the application practice,play the role of gain between some lightning protection means,through calculation and analysis,formulate practical lightning protection measures,respectively,put forward measures such as erecting lightning protection wire,replacing insulator,installing non power frequency continuous current discharge gap device.It is concluded that the best lightning protection measures considering the actual operation of the line and the characteristics of lightning resistance. |
PDF Full Text Request