A probabilistic approach to the Poffenberger-Swart bending stress of conductors subject to aeolian vibrations

Overhead electrical transmission line conductors are prone to aeolian vibrations, resulting from the alternate shedding of vortices in the wake of the cable. Aeolian vibrations are characterized by small-amplitude high-frequency flexural oscillations and, whenever not properly controlled, can induce wear damage and fatigue failures of the conductor. The standard technical approach to the assessment of aeolian vibrations and residual life of overhead conductors is based on the Energy Balance Method (EBM) and the Poffenberger-Swart formula for bending stresses. This approach relies on the main simplifying assumption of mono-modal oscillations. Typical aeolian vibration records, however, clearly show that several modes can be simultaneously excited due to wind variations in time and along the span. In this work a new approach is proposed for the prediction of aeolian vibrations of conductors within a probabilistic framework. The proposed approach allows to account both for non-linearities typical of internal damping of metallic cables and multi-modal contributions to aeolian vibrations in a straightforward and mechanically sound way. The proposed approach paves the way to a full probabilistic description of the Poffenberger-Swart bending stresses, making a further step towards a more refined definition of the expected life of overhead conductors.