STABILITY AND INFLUENCE FACTORS ON ICED CONDUCTOR WITH THE PARTICIPATION OF MULTI-ORDERED TORSIONAL MODES

A dynamic model for iced conductor describing the coupling of the first four in-plane and torsional modes has been established by applying the Galerkin method. Subsequently, the Bifurcation theory was employed to study the critical unstable condition of every mode. Galloping laws of iced conductor were analyzed under different parameters including wind velocity, torsional ratio, cable length and initial tension. Numerical procedures were finally used to verify the theoretical results. The results indicate that with the consideration of the first four torsional modes, the real parts of the eigenvalues for the first four in-plane modes experienced two Hopf bifurcations as the wind velocity increased, performing limited vibration. The increase in the torsional damping ratio could enlarge the instable region of in-plane modes. The longer cable length made a left shift of Hopf bifurcations for both in-plane and torsional modes, denoting that in-plane galloping would be substituted by the torsional ones in longer cable length. Initial tension had a remarkable impact on in-plane modes, but no obvious influence on the torsional ones. The conclusion can provide theoretical basis for conductor optimization.