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- Aerodynamic damping (1)
- Conductor cables (1)
- Freileitungen (1)
- Monitoring (1)
- Naturmessung (1)
- Nonlinear finite element simulation (1)
- Overhead transmission lines (1)
- Wind (1)
- Wind tunnel experiments (1)
- bundle conductors (1)
Investigation on the dynamic behavior of an OHL conductor bundle with light and heavy ice accretion
(2016)
Under a variety of possible cable vibrations which overhead line conductors can suffer, galloping identifies by large amplitudes at rather low frequencies. Changes of the cross-section as by ice-accretion provide the basis for such vibrations through an aerodynamic instability of drag and lift responses under wind excitation. Two different types of light and heavy ice bodies attached to a quad bundle conductor are analysed in wind tunnel tests. The results of aerodynamic drag and lift coefficients are investigated by means of a finite element model under turbulent wind excitation. It was found that instability can be well simulated for the heavy ice accretion but not for the case of lightly iced conductors.
Aerodynamic damping of nonlinear movement of conductor cables in laminar and turbulent wind flow
(2015)
It is widely accepted that aerodynamic damping is a decisive parameter influencing the dynamic response of overhead transmission line conductors in turbulent wind flow. But anyway, methods of how to account for the effects of aerodynamic damping differ significantly and so might do the results. In this work, the source of aerodynamic damping shall be revised leading to the well-known formulation for a linear pendulum being the result of the relative velocity between the structure and wind flow. Based on wind tunnel tests and validated by simulations, the differences to a pendulum movement of a sagging cable are shown. The reasons for that deviation are the large deflections, resulting in a movement non parallel to the acting wind flow. For some analysis, in particular those in frequency domain, it is practically not possible to incorporate aerodynamic damping implicitly by fluid structure interaction. If the dynamic movement can be linearized at a working point of the mean deflection, a modification to the linear approach is suggested. This approach is validated by simulation with a finite element model of an existing overhead transmission line, calibrated with onsite measurements for wind velocities at lower levels. Further accent is put on the different possibilities to incorporate aerodynamic damping in time step analysis, such as Rayleigh damping or modal damping. The differences between both approaches are emphasized and modal damping is shown to be the most adequate representation of aerodynamic damping.
Im Rahmen eines Forschungsprojekts zur Tragverhaltensstudie von Freileitungsseilen unter Böenbeanspruchung soll durch die Kombination von Naturmessungen, Windkanalversuchen und numerischen Simulationen versucht werden, das mechanische Verhalten von Freileitungsseilen und turbulenter Windbeanspruchung genauer abzubilden. Die Unsicherheiten bei der Modellierung dieses Zufallsprozesses sollen durch Windkanalversuche und Naturmessungen auf ein Minimum reduziert werden. Im vorliegenden Beitrag werden Ergebnisse von Simulationen mit den Beobachtungen aus den Naturmessungen verglichen und bewertet. Ziel des Forschungsvorhabens ist die Bewertung der aktuellen Bemessungsvorschriften für die Berücksichtigung von Wind auf Leiterseile.