Theoretical and experimental analysis of a TMD device for over head power transmission lines

The most common technology in the world for the construction of powertransmission over head lines is via suspended conductors attached to towers. As one can easily imagine, these conductors are subjected to vibrations induced by wind. The magnitude of the induced vibrations depends on the cable-wind interaction, but it’s pretty right saying that it becomes more dangerous especially when the line is in open spaces without natural obstacles (e.g. deserts, lakes, plains without woods) due to possible presence of laminar wind. With the scope of reducing the magnitude of this kind of vibrations and protect the line (and the users) from out of service, many type of dampers have been designed during the years. The thesis presented in this document analyses one of the most common devices used for this scope: a tuned mass damper invented in the ‘20s by G. H. Stockbridge, from who inherited its common name “Stockbridge” still used nowadays. This damper can cover a range from few Hz up to maximum 200 Hz with amplitude normally less than 100 mm, the so called range of Aeolian vibrations, excited byshedding of vortices in the vertical plan: it is this alternative motion in the vertical plan to cause a fatigue stress to the conductor. The investigation focuses on both modelling and experimental study of this mechanical device: the aim is obtaining the mathematical expression for the Frequency Response Function (FRF) of the damper in order to have a powerful tool for optimizing its design with a sensitive analysis, and correlate the FRF parameters thanks to the experimental data obtained in the lab tests of a prototypal damper on the shaker. All the analyses are developed in collaboration with "Officina F.lliBertolotti" S.p.A., an Italian company with long experience in manufacturing of fittings for power transmission over head lines, and with the Polytechnic of Turin, Dynamics Identification Research Group.