Study On Wind And Rain Loads Of Transmission Lines Under The Action Of Typhoon

Overhead transmission lines are the important part of the power grid,and its safe operation is decisive for the stability of the power system.Because transmission lines are usually built in the wild,they are often subjected to severe meteorological conditions which may result in various types of accidents,especially in coastal typhoon areas.Under the influence of extreme weather such as typhoons will affect the operation of the local grid and even catastrophic tower collapse accidents may occur.The failure mechanisms of lattice transmission towers under the extreme wind conditions of typhoons are not well known and such knowledge is important for the improvement of OHL(Overhead Transmission Line) design and to ensure the safe operation of transmission lines in typhoon-prone areas.From the perspective of the external loads on the transmission line under typhoon,this paper fully considers all the factors affecting the load and studies the dynamic response of the transmission line tower line system under typhoon load.According to the response result,the impacts of typhoon characteristics on transmission tower structure are analyzed.Firstly,the average wind speed and wind direction of the typhoon are solved by the YanMeng typhoon wind field based on the improved genetic algorithm(GA),and then the static load of the transmission line is determined.Based on the research above,a large number of wind speed samples are generated through numerical simulation method to predict the extreme wind speed of each wind direction in a different return period of a research point and provides guidance for the design of the transmission line.Then,considering the dynamic load caused by the pulsating characteristics of the typhoon,the commonly used pulsating wind speed spectrum is fitted with the parameters are appropriately corrected to study the pulsating wind speed spectrum suitable for a certain research point.At the same time,considering the direct additional load caused by typhoon accompanied by rainfall and the indirect influence of the surface changing of the rain-attached wire the aerodynamic parameters of the wire,the additional load of the transmission line caused by the typhoon accompanied by rainfall is studied from two aspects.Finally,taking all the above factors into account,the 2014 typhoon "Rammsasun" landed in Hainan Wenchang and caused the local continuous tower accidents as the engineering background,using ANSYS software to establish the three-tower four-line finite element model and carry out the corresponding dynamic response research of tower-line system under thetyphoon load.Firstly,considering the influence of wind direction on the force of the corner tower,the force of the corner transmission tower under different wind direction static typhoon loads is calculated.The results show that the horizontal and vertical tensions in the upward wind direction transmission line will offset some horizontal wind loads,thereby reducing the overall force of the corner tower.Subsequently,the inversion calculation of the pulsating wind and rain load on the 110 kV transmission line Baoyi ? line on the day of the accident was carried out and applied to the finite element model for calculation.The results show that,due to the turbulence characteristics of typhoon Rammasun,the dynamic amplification of the maximum axial force both in the windward and leeward sides reaches up to 284% and 266%,respectively.Then the amplification caused by the strong rainfall is calculated to be 19% on the windward legs(in tension) and 12% on the leeward legs(in compression).