Dynamic Characteristic Analysis Of Transmission Tower-line System Under Micro-topography And Micro-meteorology Conditions

With the development of the power grid,more and more transmission lines are built in mountainous areas.The transmission tower-line system has the characteristics of high flexibility and large span,and is vulnerable to extreme weather conditions in the micro-topography area.It is mainly manifested in the destruction of transmission tower and line system caused by extreme wind load,which may lead to line tripping,or even accidents such as tower overturning and line breaking.It is of great engineering significance to improve the design method of transmission line windproof and to study the response of tower-line system under micro-terrain wind field.The main contents of this paper are as follows:CFD numerical simulation method is adopted and typical wind-induced transmission tower-line system accident cases are selected.The three-dimensional wind field characteristics of pass-hillside micro-topography are studied.The research shows that in the micro-topography of the mountain pass,the acceleration effect of the narrow wind pipe near the surface is obvious,and the average wind speed in the horizontal and vertical directions is obviously increased.In the near ground of the hillside,the transverse wind speed increases greatly,while the vertical wind speed increases less.By comparing the micro-topography wind field with the flat geomorphic wind field,the wind speed correction coefficients of typical measuring points are calculated and compared with the design specifications of transmission lines.The results show that the correction coefficient of wind speed in transmission line design specification is on the small side.Based on the ANSYS platform,the finite element model of the transmission tower is established by using beam elements.The vibration characteristics of the accident tower are analyzed by modal test.The results show that the main vibration mode of the transmission tower is based on the overall oscillation of the tower head along the X and Y directions and the overall torsion along the Z direction.The wire sag is determined according to the catenary equation.The link element is used to simulate the insulator string.Based on the transmission tower model,a finite element model of the three-tower two-wire system was further established.The modal test results of the tower line system show that the vibration mode of the tower line system is dominated by the wire vibration,and the frequency is much lower than the vibration frequency of the transmission tower.The finite element simulation was carried out in combination with the CFD pass-hillside micro-topography wind field and tower line system.The wind-induced response of the transmission tower line system is calculated from two aspects:the maximum displacement of conductor deviation under wind field and deflection angle of insulator string under wind field.The flat geomorphic wind field and the micro-topographic wind field are calculated separately,and the influence of vertical wind speed is considered separately.Comparing the calculated values of the transmission line design specifications,the results show that the wind deviation design values of transmission line design regulation basically meet the requirements for flat terrain wind fields.For the pass-hillside micro-topographic wind field,because the acceleration effect of micro-topographic wind field and the existence of vertical wind speed are not considered in the specification,the design value of the specification is on the low side.