Characterising a transmission line conductor subject to free and forced vibrations

Abstract

Aeolian vibration is caused by vortex shedding due to the laminar flow of wind. It has low amplitude vibrations and is characterised by frequencies of between 3 and 150 Hz. It is the most common kind of vibrations in transmission lines. Since it occurs in the vertical plane, it causes alternating bending stresses, leading to eventual failure of the conductor cable. The study characterised free and forced vibrations of the Tern and ACSR Bersfort conductors. This was done according to IEEE Standards and general research on line conductors according to CIGRE guidelines. The characterisation experiments were conducted at the University of KwaZulu-Natal’s Vibration Research and Testing Centre (VRTC). The study was conducted to confirm the findings of a 2011 study by Mokeretla, which suggested that the Tern and ACSR Bersfort conductors’ self-damping characteristics could not be able to suppress Aeolian vibrations. The study found that the damping factors for forced and free vibrations on the Tern conductor were ≤ 0.02181 and ≤ 0.236, respectively. Also, it found that the damping factors for forced and free vibrations for the ACSR Bersfort were ≤ 0.024807 and ≤ 0.232, respectively. These findings suggest that the natural damping of the Tern and ACSR Bersfort conductors cannot suppress aeolian vibrations. Thus, this study collaborates the findings of Mokeretla.