High accuracy measurement of deflections of an electricity transmission line tower

• Geodetic measurement of dynamic deflections of a lattice tower.
• Wind and cable-induced vibrations.
• High-accuracy measurements in a complex structural system.
• Hostile environment, unique opportunity for measurements.
• Dominant frequencies and constraints to structural analysis.

The displacements of the top of an H-type, 30 m-high lattice tower of a 150 kV electricity transmission line have been measured using a Robotic Total Station (RTS). Horizontal displacements approximately up to 30 mm and vertical up to 8 mm have been measured on a passive reflector set on the tower top during days with moderate wind. Measurements are reliable and above the noise level which is determined from measurements in a second reflector near the stable base of the tower. Displacements in the cross-wind direction were found larger than along the wind. Such measurements, probably the first to be made in a pylon, may be used to constrain models of their dynamics controlled by a very large number of unknown parameters.