Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 114796

114796 - Power Transmission Lines Vibration Analysis From Karman Vortex Shedding, a Case Study 

Overhead power transmission cables are exposed to a variety of weather phenomena which can deteriorate conductors and even cause them to fall, thus causing power outages and other problems. One of the weather elements responsible for this is the action of the wind.
This phenomenon can give rise to failures due to fatigue stresses and even short circuits due to direct contact or approximations between bare conductors.
Cables are structures that are characterized by low internal damping, low rigidity, and low weight and due to this they are not capable of dissipating the total excitation energy, therefore they can reach large vibration amplitudes.
It is important to highlight that the transmission and distribution lines present a non-linear and highly dynamic behavior in the presence of wind vibrations. Therefore, a rigorous and detailed analysis is required to guarantee the safety and reliability of the electrical system.
There is a variety of vibrations depending on the layout of the lines. This article specifically studies power transmission lines vibration analysis from Karman vortex shedding. Also, it is analyzed the damping response of drivers subjected to such vibrations, considering the influence of suspension and fastening structures.
Karman oscillations originate when wind flows over an obstacle and creates vortices in its wake, which can induce vibrations in the line when the wind speed approaches the natural frequency of the structure. In this situation, vortices appear on the side of the obstacle opposite to the flow and alternately detach, forming a Von Kármán Vortex Street. These vortices create areas of low pressure and cause the object that forms the obstacle to suffer forces that tend to move it alternately towards the areas of low pressure.
Some factors that influence the intensity and frequency of oscillations include wind speed and direction, line geometry, and environmental conditions.
To mitigate the effect of wind vibrations, there are damping systems such as Stockbridge dampers, SVD Dampers and Damper Spacers, which have the purpose of dissipating the energy absorbed by overhead conductors. These systems must be dimensioned according to the conditions to which both the phase lines and the guard cables will be subjected.
A theoretical-computational study on the behavior of resonant oscillations from Von Karman vortices is presented, through computational fluid dynamic modeling of an HTLS, i. e., high temperature, low sag type distribution power line. The analyzed test section is between two towers with 500m distance between them and, a distance between cables of 3.5m. The outer diameter of these cables was 6.64 mm.

Presenting Author: Veronica Correa Facultad de Ingeniería - Universidad Nacional de Asunción

Presenting Author Biography: Senior undergraduate student from the Electromechanical Engineering Department at Universidad Nacional de Asuncion.

Authors:

Axel Ibañez Facultad de Ingeniería - Universidad Nacional de Asunción
Santiago Schaerer Facultad de Ingenieria - Universidad Nacional de Asuncion
Veronica Correa Facultad de Ingeniería - Universidad Nacional de Asunción
Enrique Gimenez Facultad de Ingeniería - Universidad Nacional de Asunción
Matias Fernandez Ferreira Facultad de Ingerniería - Universidad Nacional de Asunción
Marcos Lorenzo Vera Bower Facultad de Ingenieria - Universidad Nacional de Asuncion
Jorge Kurita Facultad de Ingenieria - Universidad Nacional de Asuncion