Prediction and characterization of three-dimensional multi-mode coupled galloping of multi-span ice-accreted transmission conductors

Abstract

This study presents a nonlinear analysis framework of three-dimensional galloping of multi-span ice-accreted transmission line conductors suspended by insulators. The vertical, lateral and torsional conductor displacements are described by modal displacements with mode shapes of single span conductors, and the insulators are modeled as pendulums. The aerodynamic forces on the conductor are modeled using quasi-steady theory. The linear equations of motion with respect to the static equilibrium are also derived. The analysis framework is applied to two- and three-span four-bundled ice-accreted transmission conductors with complex eigenvalue analysis and response history analysis. A harmonic balance approach is also proposed for a direct calculation of steady-state galloping response. The accuracy and efficiency of the proposed frameworks are verified using the results estimated from a finite element model. The similarities and differences of galloping characteristics, i.e., initiation condition, steady-state amplitude, dynamic tension, between single- and multi-span conductors are investigated. The role of suspension insulators on multi-span galloping is clarified. The longitudinal motions of insulators result in reduced vertical modal frequencies of conductor, thus lead to different galloping characters. The galloping of multi-span conductors with closely spaced modal frequencies can be initiated from multiple modal branches with a beating phenomenon.