An Appraisal of Modelling Strategies for Assessing Aeolian Vibrations of Transmission Lines

Assessment of Aeolian vibrations of overhead electrical conductors and guard wires is a relevant technical problem, usually solved through an application of the Energy Balance Method (EBM). The reliability of the EBM results can be strongly affected by the criteria adopted to define the input data (e.g. the wind power) as well as by the modeling assumptions adopted to describe the dynamics of the line. The present paper investigates the effects of different modeling strategies on the outcomes of the EBM. The transmission line spans are modelled through a dynamic substructuring approach: the mechanical impedance matrix of each structural element (e.g. the cables) is defined through a continuum approach and then assembled to lumped components (e.g. the dampers) to obtain the impedance of the overall system. Natural frequencies and mode shapes are then determined through a forced vibration method, which allows to easily handle non-proportional damping, typical for the problem at study. Different structural models to describe both the cables and the passive damping devices are presented. Several different strategies to model the wind power input and the self-damping of the cables are also considered for comparison purposes. The proposed formulation is then applied, within the framework of the EBM, to estimate the aeolian vibration amplitude of some well documented power lines, for which experimental data are available in the literature.