| UHVDC transmission project has its unique advantages like large transport capacity;high power supply;high transport efficiency and long conveying distance(as it can solve the problem of optimize the allocation of resources).since the continuous development of UHVDC project like the long line corridor.There is a high risk of the UHVDC lines suffered by lightning when the circuit goes through a complex landform and the lightning climate is changeable.Therefore,the lightning protection research of UHVDC project cannot be ignored.Therefore,it is very important to study the lightning protection of the UHV transmission line in order to put forward scientific lightning protection measures.This thesis first discusses the principle and calculation methods of lightning protection lightning overvoltage is formed,with the wine lake Hunan section of UHVDC transmission lines as the research object,in-depth study of the tower,topography,grounding resistance,external insulation level,climate and other factors on the lightning protection performance.ATP-EMTP electromagnetic transient simulation program and established a lightning back-flashover model of UHVDC transmission line in JiuHu line,Hunan province.The simulation results show that the lightning strikes performance of UHVDC transmission lines is related to the height of the tower pole,the grounding resistance of the tower,and the level of the insulation outside the line.The higher of the tower,the grater scope of the tower triggered lightning,the higher rate of the tower to counterattack,the higher rate of the counterattack flashover;Grounding impedance value across the cross-over voltage attenuation rate,the greater of the ground impedance value,the higher of the rate of the counterattack flashover.Icing,rainwater,PH value and pollution directly affect the external insulation level,so that the insulator is vulnerable to breakdown and the counterattack flashover rate increased.The lightning stripping performance of the UHVDC transmission line in JiuHu line,Hunan is analyzed by EGM,which is more suitable for the terrain along the corridor along the corridor of Hunan province,and the influence of line working voltage and wind speed along the corridor is taken into account in EGM.The analysis shows that the lightning stripping performance of UHVDC transmission lines is highly correlated with line working voltage,terrain and topography along the corridor,lightning protection angle,wind speed and transmission line.Considering the operating voltage and regardless of the working voltage,both the lightning level and the flashover rate are significantly different,regardless of the working voltage of the lightning level was significantly higher than the wire to consider the working voltage;ground angle of more than 15 degrees,Significantly increased;the smaller the protection angle,the smaller the degree of damage to the flashover,from the time,the flashover rate increased by 1.7 times.The greater the protection angles of the lightning protection line,the shorter the protection arc and the increase of the exposed arc area,so the greater the flashover rate is.When the wind speed is from 10m/s to 25m/s,the protection angle of the outer negative conductor is negative The angle of change into a positive angle,the damage from the flashover rate from 0.0511 times/(100km.a)increased to 1.1073 times/(100km.a).And the wind speed increases so that the inner side of the positive polarity of the wire protection angle is getting smaller and smaller,with the ground slope of the shielding effect,the inner polarity of the wire collision flashover rate of 0.The conclusion of this thesis has the reference value for the lightning protection of UHV DC project in Hunan section of the lake,and provides a theoretical basis for the development of scientific lightning protection measures. |
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