Studies On Bifurcation Characteristics And Limit Cycle Oscillation Of Subspan Oscillation For Two Bundled Conductors

The wake-induced oscillation of transmission lines caused by wake effects of bundled conductors is a self-excited vibration with medium frequency and amplitude. It is caused by a mutual interaction between fluid and structure, is generates complex flow-structure coupled movement. Bundled conductors are widely used in power transmission engineering. However, wake-induced oscillation of transmission lines is very severe under the action of wind load. It has great damage on power transmission engineering. So in order to prevent the occurrence of oscillations and ensure the safe operation of the transmission project, it is necessary to do deeply research in wake-induced oscillation of transmission lines. so many researches about wind-induced vibration of overhead transmission conductor have been done. Usually, wake-induced oscillation is explored by wind tunnel experiment, which cost much and spends long time. While theoretical research and simulation calculation of wake-induced oscillation is not thorough. Research literatures of the wake-induced oscillation of transmission lines were studied. This paper investigates the stability and bifurcation happen in the two bundled wake-induced oscillation of power transmission lines.Firstly, the governing equations of the subspan oscillation system are established. Then central manifold theory is used to reduce the dimension of the subspan oscillation system, and limit cycle oscillations near these two Hopf bifurcation points are also obtained. two points of instability velocity are obtained too. The stability of limit cycle oscillation is acquired between two Hopf bifurcation points. The successor function method is used to analysis the types of the Hopf bifurcation points. Then, Subspan oscillation model of the leeward conductor lying in the wake of the windward conductor is given. the incremental harmonic balance method(IHB) is used to derive function of solving high-order limit cycle oscillation of subspan oscillation system, and limit the first three harmonics response of cycle oscillation of subspan oscillation system are obtained. The result show that subspan oscillations exist only in a certain range of wind velocity. With the increase of harmonics, the impact of higher harmonics significantly weakened. The results of first harmonic agree with numerical results of Runge-Kutta well. The influence of span and original position of the leeward conductor to subspan oscillations has been analyzed, which provide the technical support for measures to prevent the subspan oscillation. Lastly, Mechanical and FLUENT are used in the ANSYS Workbench, flow-structure interaction of the wake-induced oscillation of two bundle conductors is solved. Geometry, Fluid Flow(Fluent), Transient Structural and System Coupling are used, the dynamic response of the wake-induced oscillation of two bundle conductors is researched in the whole span. Analyzed the phenomenon of the wake-induced oscillation of two bundle conductors under different wind speed deeply.Through analyzing the bifurcation characteristics and limit cycle oscillation of two bundled conductors, this paper reveals the vibrating mechanism and analyzes the effect of environmental and structural parameters on the oscillation system. The investigation provides meaningful references for inhibiting the oscillation of bundled conductors, which is of significant theoretical and applied meanings.