Wake-induced oscillations The Dance of the Wires

Wake-Induced Oscillations

This document explores the phenomenon of wake-induced oscillations, particularly in bundle conductors where aerodynamic interactions lead to various types of motion. These oscillations are significant in understanding the behavior of conductors under wind influence and their potential impact on structural integrity over time.

Wake-induced oscillations are primarily observed in bundle conductors, where some sub-conductors are situated in the wake created by those positioned to the windward side. This arrangement results in a shielding effect, where the windward conductors influence the aerodynamic behavior of their leeward counterparts. Four distinct types of wake-induced motion can be identified: sub-span mode, vertical galloping, horizontal galloping, and rolling.

The oscillation mechanism is fundamentally driven by the wake, which reduces drag coefficients on the leeward sub-conductors while simultaneously generating lifting forces. As a result, the leeward conductor begins to oscillate. Due to the presence of conductor spacers within the bundle, this movement is transmitted to the windward conductor, causing it to participate in the oscillation as well.

Although these vibrations typically do not cause significant reductions in phase-to-phase distances, they can absorb a portion of the mechanical power from the wind. This absorption can lead to fatigue in the conductors, especially when the oscillations occur repeatedly over extended periods. Understanding these dynamics is crucial for the design and maintenance of overhead power lines and similar structures subjected to wind forces.