Research On Lightning Overvoltage Analysis And Suppression Method Of Half-wavelength AC Transmission Line

In order to solve the problem of energy globalization and to promote the supply and demand relationship of energy internal circulation,ultra-long-distance and large-capacity transmission will become the main global energy transmission method in the future.UHV half-wavelength AC transmission refers to the AC transmission mode with voltage level of1000 k V and above and the transmission distance is exactly equal to half the wavelength length of the working frequency.Half-wavelength AC transmission technology has some unique advantages of its own,such as electrical distance can be equated to 0,large transmission power,no reactive power compensation and other unique advantages.However,due to the high voltage level of the half-wavelength transmission line,when a lightning strike occurs,the line will cause a very high overvoltage,if not timely suppression of overvoltage,will endanger the safety of substations and electrical equipment,so this paper focuses on the study of overvoltage caused by lightning strike half-wavelength line and its lightning strike overvoltage suppression strategy research.In this paper,the line-related models(e.g.,tower,insulator,and lightning models)of the EHV transmission line are first constructed using PSCAD/EMTDC electromagnetic transient simulation software.Based on the simulation model,the overvoltage distribution is analyzed when four lightning strikes occur on the line(i.e.,lightning strike bypass fault,lightning strike bypass unshorted,lightning strike backfire fault,and lightning strike backfire unfaulted).In this paper,a zinc oxide arrester(MOA)is selected to suppress overvoltages generated on half-wavelength transmission lines.As a gapless oxide arrester,its excellent voltammetric characteristic curve,has a better suppression of overvoltage effect.Its voltammetric characteristics lie in the normal operation of the line is equivalent to open circuit(the current flowing through the MOA is very small);in the line when the voltage exceeds a certain threshold value,the MOA resistance drops sharply,releasing energy,followed by the role of energy discharge.Based on the lightning overvoltage problem on the UHV semi-wavelength transmission line,the use of zinc oxide surge arrester on the initial arrangement strategy for lightning overvoltage suppression and simulation to verify the feasibility of the program,roughly divided into two steps: first consider the economics of the premise that every300 km arranged a group of surge arresters,found that the suppression effect does not work,then every 100 km arranged a group of surge arresters,to optimize the arrangement strategy to achieve suppression The purpose of lightning overvoltage.Then the actual situation and the actual thunderstorm situation combined with the simulation of heavy lightning area,proposed lightning overvoltage suppression strategy and simulation to verify its suppression effect.As the actual line,it is not possible to have just 3000 km of transmission lines,so on the basis of the natural half-wavelength line,the tuning module containing tuned half-wavelength line is introduced and simulated and analyzed under the distribution of tuned half-wavelength lightning overvoltage,through the distribution of lightning overvoltage on the line,the initial arrangement strategy containing tuned half-wavelength line overvoltage suppression is proposed,simulation to verify its suitability,if not feasible,further proposed to modify and improve the program,so that the proposed program has a good suppression effect in four lightning strikes,and then simulation to verify the feasibility of the program.