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Investigation on Nonlinear Characteristics of Iced Quad Bundle Conductors Galloping

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Tutor: LiuXiJun
School: Tianjin University
Course: General and Fundamental Mechanics
Keywords: Bundle conductor,Galloping,Spacers,Average method,Singularity theory
Type: Master's thesis
Year:  2012
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Galloping of iced transmission conductors is a self-excited vibration with lowfrequency and large amplitude under the action of wind load, which can result in thefailure of conductors, flashover between sub conductors and even also the destroy ofthe insulators, hardware and components of tower and so on, all of these can brings agreat challenge to the national economy and security. Thus, the investigation on icedconductor galloping has a very important significance in theory and practice. Thispaper focus on the iced quad bundle conductors, and the main work includes thefollowing several parts:(1) The iced quad bundle conductors are simplified as a single conductor, inwhich the effect of spacers stiffness and damping is considered. Then a continuumdynamics model for iced quad bundle conductors of three degrees of freedom invertical, horizontal and torsional directions is established by means of the Hamiltonprinciple, and the final dynamic equations of conductors and spacers are derived.Simultaneously, the torsional stiffness of bundle conductors is fitted to a cubicpolynomial function.(2) The numerical analysis for dynamic equations of system is achieved and thedisplacement and time curves and amplitude-frequency curves are also obtained andso on. Then the influence of related parameters about fluid density, damping ratio,line span on galloping amplitude and critical wind velocity is analyzed. The relationcurve between elastic properties of spacers and conductor galloping is obtained. Theresults indicate that the conductor galloping can be weakened to some degree with theproper enlargement of horizontal damping ratio, the reasonable increase of the massper unit length of conductor, the proper decrease of the length of transmission span,the reasonable setting of spring stiffness and damping on spacers and the avoidance ofareas such as the wind outlet and windward as much as possible when choosing theline path and so on.(3) In order to avoid the complexity of strongly nonlinear analysis, the conductortorsional vibration response is fitted to a cubic polynomial function. After substitutingit into the vibration equations of vertical and horizontal directions, the stronglynonlinear system can be translated into the weakly nonlinear system. Then by using the average method, the vibration of system is analyzed corresponding to thenon-internal resonance,3:1internal resonance and1:1internal resonance respectively.Finally, the influence of related parameters such as wind velocity, horizontal dampingratio, fluid density, line span on conductor galloping and the response curves ofconductor galloping to the variation of different parameters are obtained. The resultsshow that the approximate analytical solution of system is basically consistent withthe numerical solution.(4) The bifurcation equation is analyzed by using the singularity theory and thecorresponding transition sets and bifurcation diagrams of system are obtained. Thenswitching the unfolding parameter plan of system to the physical parameter plan, theplanar graphs of physical parameter are obtained. It can be seen that the stability ofequilibrium state is changed and the bifurcation of orbits of the solution of equation isappeared. Thus, we can identify the mechanical properties of this nonlinear systemdeeply.
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