Vibration Characteristics And Vibration Reduction Of Transmission Tower-line System Under Gust Excitation

High-voltage transmission tower-line system has the characteristics of light weight,high flexibility and small damping.It is sensitive to earthquake and wind,and is prone to vibration fatigue damage and dynamic collapse under extreme conditions.Among them,the problem of transmission tower vibration caused by wind load,especially typhoon,is more prominent.In this paper,the inherent characteristics of transmission tower-line system and the vibration suppression of transmission tower are studied by using finite element model analysis and testbed test.Firstly,the finite element model of transmission tower-line system is established by using beam-pole hybrid element.The modal analysis of transmission tower,transmission line and "two towers and three lines" system is carried out,and the inherent characteristics of the system are obtained.The modal test is carried out on the test bench by hammering method.The test results are in good agreement with the finite element analysis.At the same time,the influence of suspension of transmission line,insulator state and vertical of transmission line on the natural frequency of transmission tower is studied on the test bench.Secondly,the stress-strain analysis of the transmission tower is carried out.In the test,the stress distribution of the transmission tower is obtained mainly by electrical measurement of resistance strain gauge,and the stress state is obtained by strain gauge.The stress analysis of the transmission tower is carried out after the signal is transmitted to the node through the full bridge circuit.At the same time,the stress analysis of the transmission tower is carried out on the finite element model,which is in good agreement with the test results.Then the actual transmission tower model is established,and the wind-induced vibration response of the transmission tower-line system,the fatigue life of the transmission tower under wind load and the mechanical properties of the transmission tower under the condition of line disconnection are studied.Based on the harmonic superposition method,the fluctuating wind load is simulated,and the wind load is loaded on the finite element model of the transmission tower.The general rules of the displacement and stress responses of the transmission tower under the wind load are obtained.The stress response of transmission tower under random wind load is analyzed by rain flow counting method,and the fatigue life of transmission tower under wind load is calculated by P-S-N curve.At the same time,the mechanical properties of transmission towers under the condition of line breakage caused by typhoon are analyzed.Finally,according to the stress distribution characteristics of transmission tower and the response characteristics of wind load,a composite pendulum tuned mass damper(TMD)device is designed to suppress the first-order vibration mode of transmission tower.Composite pendulum TMD consists of springs,mass blocks and adjustable dampers.It is installed on the cross-arm of the transmission tower test-bed,and its mass,stiffness and damping are designed through parameter optimization analysis.The test results show that the device can effectively suppress the first-order vibration of the transmission tower.