Abstract
A new calculation method of critical wind speed based on three degrees of freedom (3-DOF) is proposed for galloping problem of iced transmission line. Based on the quasistatic theory, the aerodynamic load of iced transmission line is obtained, which considers the influence of transverse and torsional motion on the relative wind angle of attack. Finally, the equivalent galloping model of 3-DOF iced transmission line is established. At the initial angle of attack, the aerodynamic load is expanded by Taylor, and the unsymmetrical linear aerodynamic coefficient matrix is obtained. The Routh–Hurwitz criterion is used to judge the stability of iced transmission line system, and then the critical wind speed is calculated. The in-plane and out-plane frequencies corresponding to the first-order mode of the transmission line are solved by the analytical method and numerical simulation method. The results obtained by the two methods are compared and verified. The influence of dimensionless transmission line parameterλon the in-plane and out-of-plane frequencies is discussed. The aerodynamic coefficients of the iced transmission line are measured by wind tunnel test and the aerodynamic characteristics are analyzed. According to the theoretical formula, the critical wind speed is calculated by MATLAB. The critical wind speed determined in this paper is compared with the critical wind speed determined by Den Hartog and Nigol theory. The influences of torsional vibration frequency, ice thickness, and ice shape on critical wind speed are analyzed. The research results of this paper have important theoretical significance for the stability judgment of iced transmission lines.
Highlights
Galloping is the self-excited vibration of transmission line under the action of wind load [1]
The new mechanical model of the 3-DOF iced conductor is established, and the aerodynamic coefficient is expanded by Taylor at the initial angle of attack. e galloping vibration of the iced conductor under static wind is studied, and the vibration equation of the 3-DOF iced conductor is obtained by neglecting the inertia coupling term and the load stiffness term
In the wind tunnel test, different wind speeds, ice thicknesses, and ice shapes are set. e aerodynamic coefficients in three directions of the iced conductor are measured by wind tunnel test
Summary
Galloping is the self-excited vibration of transmission line under the action of wind load [1]. Is theory considers the main vibration of transmission line but ignores the influence of horizontal vibration and torsional vibration on galloping. Later, based on this theory, Parkinson [5], Davenport [6], and Iwan [7] developed this theory. Is theory considers the eccentric coupling and ignores the influence of lateral vibration on galloping of transmission lines. As far as the author knows, considering the changes in wind field and conductor position at different times, the galloping mechanical model of the iced conductor with three degrees of freedom has not been studied. Based on the quasistatic theory, a 3-DOF vibration mechanical model for galloping of the iced conductor is established in this paper. Based on the quasistatic theory, a 3-DOF vibration mechanical model for galloping of the iced conductor is established in this paper. e influence of the conductor structure parameters on the stability of the iced conductor is studied. e critical wind speed of the iced conductor is calculated by MATLAB software based on the stability discriminant
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