Identification and analysis of experiment-driven model for galloping in multi-conductor transmission lines

Galloping instability is considered to be one of the most important wind-induced effects in overhead transmission lines which can cause severe damage or forced outages. The improved understanding of this phenomenon and the associated predictive capabilities are at the centre of ongoing research. The use of minimal dynamic models and high level of modelling abstraction allows to narrow the analysis on the critical factors influencing this phenomenon. Among these, owing to its complex physics, the characterisation of aerodynamic loading associated with the rotational activity of a multi-conductor bundle in cross-flow has traditionally relied on crude assumptions regarding the location of the aerodynamic centre. This work aims to determine and assess the location of this point under the angular reorientation of a four-conductor bundle within a newly developed identification framework, leveraging two established mathematical models and experimental data. The damping matrices corresponding to the two chosen models are correlated and the least square optimisation problem is formulated to identify the location of the aerodynamic centre. Under the gradually increasing bundle angular reorientation, it is found that, whilst the aerodynamic centre maintains a direct upstream azimuthal orientation, the distance from the geometric centre of the bundle fluctuates significantly. The resulting updated model, which uses the new configuration-dependent aerodynamic centre specification, is then successfully validated against the reference model and experimental data with the aim to be eventually transferred to real-world scenarios in industry. Based on the obtained characteristics, it is suggested that the configurational dependency of the aerodynamic centre is caused by the combined influence of the cyclic symmetry and aerodynamic shadowing between the upstream and downstream cables inherent to the multi-conductor bundles. • Galloping instability has a major impact on the design of transmission lines. • Eigenvalue analysis is used to find analytical solutions for galloping stability. • An aerodynamic centre represents rotational motion when using quasi-steady theory. • The galloping instability is mainly driven by the mean torsional displacement. • The critical wind speed is governed by the lift force acting on the body.