| As the lifeblood of China's power transmission,high-voltage transmission lines have made outstanding contributions in solving the uneven distribution of power resources,easing energy-intensive areas of energy tension.In recent years,with the continuous development of China's UHV project,HV transmission lines not only carrying the burden of traditional power transmission,but also support the development of nuclear energy,wind energy and other clean energy.In order to ensuring the safe and reliable operation of the power system,it is necessary to ensure the safety and reliability of transmission lines' operation.However,due to the distribution of economic centers in China and the geographical factors,some EHV transmission lines are inevitably erected in the wilderness,mountains and other places exposed to the natural environment,thus increasing the probability of suffering from natural factors.Among the natural factors which affect the operation of transmission lines,lightning accidents have the greatest impact.According to the statistics of 220 kV and above transmission lines,40% to 70% of tripping accidents are caused by lightning.Lightning has become a major threat to the safe operation of transmission lines,seriously affecting the safety and reliability of transmission lines and power systems,so dealing with the lightning protection work to improve the lines' mine level is very meaningful.The main work and achievements of this paper are as follows:(1)Analyzed the significance and principle of lightning protection of high voltage transmission lines,the development course and main measures of lightning protection.The development process of lightning protection of transmission lines is analyzed from four stages,the principle of lightning protection of transmission lines and the lightning protection measures which are mainly used in engineering are studied,which laid the foundation for the follow-up work.(2)The principle of lightning overvoltage and its calculation method are studied.In order to study the lightning protection measures of transmission lines,the characteristics of different stages of lightning discharge and the lightning current waveform applied in engineering calculation are analyzed,which provided the theoretical basis for the proposed lightning protection measures.At the same time,the calculation method of lightning overvoltage and induced lightning overvoltage are studied,and Analyzedthe factors influencing the lightning protection level.(3)For the two lightning accidents of 500 kV Yangbei ? line in recent years,through analyzing the basic situation of the fault line and the weather conditions and lightning location at that time to judge the lightning strike position,and carried out on-site treatment.Through twolightning accidents,the lightning protection level of the transmission line of Yangbei ? line is studied,and the improvement measures are proposed.(4)Finally,this paper built an 8-pole 500 kV EHV transmission circuit simulation model on the ATP / EMTP platform.Aiming at the situation of lightning protection measures in Yangbei ? line transmission line,the feasibility of installing lightning arrester to improve the level of mine line is verified by simulation.The results show that the lightning arrester can greatly improve the line lightning protection level,even when the grounding resistance is large,the line lightning level is enough to meet the engineering design requirements,it has some reference value of 500 kV EHV line lightning protection design. |
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