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Eingeladener Vortrag (wissenschaftliche Konferenzen)
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MOSYTRAF - Monitoringsystem zur Tragverhaltensstudie von Freileitungen unter Böenbeanspruchung
(2014)
Im Rahmen des Forschungsvorhabens MOSYTRAF (Monitoringsystem zur Tragverhaltensstudie von Freileitungen unter Böenbeanspruchung)
werden seit Ende 2011 kontinuierlich Windgeschwindigkeiten entlang eines insgesamt 800 m langen Freileitungsabschnitts gemessen. Gleichzeitig wird die resultierende Windkraft aus Wind auf Leiterseile an den Isolatoren erfasst. Dadurch soll der Zusammenhang zwischen Einwirkung und Bauwerksreaktion möglichst zuverlässig ermittelt werden. Dabei ist besonderes Augenmerk auf die kurzzeitigen
Windgeschwindigkeitsspitzen, die Böen gerichtet. Diese erfassen anders als die konstante mittlere Windgeschwindigkeit, nicht die gesamte Länge des Freileitungsabschnitts, sondern nur einen eingeschränkten Bereich. Aus diesem Grund erfolgen die Windmessungen an insgesamt 13 Stellen entlang des Abschnitts und geben ein fein aufgelöstes Bild des Windfeldes. In dem Beitrag werden Messergebnisse beispielhaft präsentiert und einige Plausibilitätskontrollen vorgestellt, da dies einen unerlässlichen Schritt bei Naturmessungen darstellt. Ausgehend von einem Übersichtsdiagramm der bisherigen Messergebnisse wird die Aufgabenstellung und die Zielsetzung der Messkampagne erörtert.
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.
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.
Windeinwirkungen auf Freileitungen wurden in der Vergangenheit meist an exponierten Standorten bestimmt. In einem Langzeitversuch wurden seit 2012 an einer mit moderner Messtechnik ausgerüsteten 380-kV-Leitung der 50 Hertz Transmission GmbH, die im nicht besonders exponierten Gelände verläuft und somit den Leitungen im Netz entspricht, die Windgeschwindigkeiten entlang der Leiter und deren Auswirkungen auf die Stützpunkte gemessen. Die Messungen und die begleitenden Auswertungen bestätigen die heute verwendeten normativen Vorgaben für die Windwirkung auf die Leiter von Freileitungen, soweit dies in der relativ kurzen Zeit von fünf Jahren möglich ist.
Overhead transmission lines are very sensitive structures in regards to wind action. The cables, spanning over a few hundred meters contribute in particular to the overall action on the suspension towers. These slender structures incorporate both structural nonlinearities from the large deformation of the cables and aerodynamic nonlinearities which need to be accounted for when it is to estimate the system response to strong wind events. In this work, a finite element procedure is presented to model an existing power line section using nonlinear cable elements. The wind force is assumed quasi-steady with force coefficients determined in wind tunnel test on a conductor section. Further, aerodynamic damping is incorporated by considering the relative velocity between cable nodes and oncoming wind flow. The results are compared with on-site measurements of the cables support reaction. The results show a significant effect of damping since almost no resonant amplification is visible both in observation and simulation. In addition, wind tunnel tests approved aerodynamic damping to be large for the system of sagging cables, but nonlinear in its nature. It is concluded, that the dynamic response of overhead transmission line cables has to be modeled with care, considering all sources of nonlinearities. That is of particular interest in case of random excitation such as wind because the peak response depends on the probability distribution of the system's response.
MOSYTRAF-Monitoringsystem zur Tragverhaltensstudie von Freileitungsseilen unter Böenbeanspruchung
(2014)
Overhead transmission line cables under wind gust loading - measurements and numerical simulations
(2014)
Overhead transmission lines with conductor cables spanning over a few hundred meters are highly sensitive to the action of wind. Particularly wind acting on the cables signifies a major load on the suspension towers. In order to identify critical loading parameters and the load-response mechanism of those structures, measurements are carried out along a high voltage overhead transmission line capturing the acting wind field as well as the structural response of the cables. A finite element model of the structure is built and used to simulate the system's response. A method is presented which allows generating a complete wind field for all the models nodes incorporating measured wind velocities and estimated parameters of the acting wind. The full scale measurements of both action and reaction will be compared to the numerical results.
