The detection and damping of overhead-line conductor vibration

Overhead-transmission-line conductors are peculiarly prone to aeolian vibration generated by eddy vortices formed as the wind passes across the conductor. Unless steps are taken to reduce this vibration, failure of the conductor by fatigue wear at the clamp may occur after a few years´ service. The various methods of detecting vibration are reviewed. These include vibrating-mass recorders, directly-coupled pen recorders, electromagnetic transducers, resistance and piezo-electric strain gauges, and piezo-electric accelerometers. The dampers described include: (a) Tuned dampers: pneumatic, hydraulic, spring and suspended-weight (Stockbridge) types. (b) Impact dampers: vibrating-pad, vibrating-lever, plastic-tube and plastic-spiral types. (c) Reinforcing devices: armour rods, festoons, cable absorbers, tape and springs. (d) Special conductors. Details are given of experimental work performed on 33, 132, and 275/380kV lines to detect and damp vibration. For convenience, vibrating-mass recorders were used. The damping efficiencies of several types of damper are given, the vibration of twin-conductor bundles is compared with that of single similar conductors, and the vibration characteristics of special steel-cored-aluminium conductors are examined. Data are also given on the effectiveness of various arrangements of dampers fitted to the very long spans across the Rivers Usk and Severn, and a method is suggested for damping such long spans with multiple Stockbridge dampers.