Energy Method to Compute the Maximum Amplitudes of Oscillation Due to Galloping of Iced Bundled Conductors

The paper presents a modal model to describe the interaction between a 4-conductor bundle and wind. A finite-element model of the bundle is used to perform a linear analysis, to extract mode shapes and natural frequencies of the system. The motion of the expanded bundle is then described through mode coordinates representing the first horizontal, vertical and torsional modes. Wind tunnel tests were performed adding templates over the cables to mimic the presence of ice over the same conductor bundle; tests allowed to characterize the aerodynamic coefficients of the entire bundle and provided data for the model validation. The model was then applied to a case study to predict the maximum oscillations produced by iced conductor galloping. Time-domain simulations were used for the purpose, together with an alternative approach named energy method; this last directly estimates the amplitude of limit cycles avoiding the integration of the equations of motion and can be much more useful from the engineering point of view.