The computational investigation of the wind-induced vibration of overhead conductors.

Abstract

The reliable transmission of high-voltage electricity through overhead electrical conductors is a cornerstone of the modern industrialised world. Any situation or phenomenon that impedes the functioning of this network warrants investigation. An example of which is the occurrence of aeolian vibration. This is caused by airflow over the conductor breaking off into alternating turbulent vortices. These vortices can cause an alternating lift force on the conductor, resulting in unwanted vibrations and damaging fatigue loading. The Vibration Research Testing Centre (V.R.T.C.) of the University of Kwa-Zulu Natal is investigating the effects of this problem experimentally by oscillating an overhead conductor in a test facility. An electrodynamic shaker is used in a frequency and amplitude range equivalent to that produced by measured wind power input. This method is limited because only a single point force input to the conductor is possible as well as the limited span length. The aim of this research was to investigate the effects of aeolian vibrations and to develop a model that can verify the results of the V.R.T.C. This model can also be used to analyse scenarios that cannot be experimentally tested. A mathematical simulation of an overhead conductor subject to various wind power and single point oscillator inputs was developed. The mathematical simulation was performed using the MATLAB computing environment in the form of a finite element model. The model consists of a number of beam elements, arranged linearly to form a cable model, with suitable end conditions and driving inputs. The system was solved using a varying time-step 4th order Runge-Kutta solving method. The results of the model were compared to tests performed at the V.R.T.C. on a sample conductor length.