Vibration of overhead line conductors

This paper is a resume of available data concerning the causes of and remedies for wire failure in overhead line conductors subject to the ?eddy? vibration due to steady winds ranging from 5 to 25 m.p.h. The theory of eddy vibration is first outlined and tests are detailed dealing with the effect on wire failure of such factors as tension and the design of clamp and conductor. Studies of clamp and conductor motions during vibration are also described. It is shown that wire failure is caused mainly by the ?nicking? action between wires occasioned by the clamping stresses, and to a lesser degree by the ?hammering? between conductor and clamp. The ?nicking? weakens the wires locally and thereby prevents full use being made of their fatigue strength. Though it is difficult to reduce the ?nicking? action, other data showed that a reduction of wire failure could be obtained by a lowering of the working tension, and that the effects of ?hammering? could be reduced by a suitable design of clamp. Geographical factors favourable to vibration are then discussed, and data are set out which indicate that in general light and hollow conductors are more susceptible to vibration than other types. The ?non-vibrating? conductor due to Preiswerk is also described. A discussion then follows of the various methods which have been employed in practice to reduce wire failure (i.e. methods of reinforcing the conductor at the clamp against the bending caused by vibration, the use of dampers, festoons, etc.). All.these methods have been more or less successfully employed, and each has its advocate. It appears, however, that wire failure can be reduced by a suitable application of either, though it has not been found possible to make a definite statement concerning their relative costs, which in any case must depend on local conditions. In recent years, however, the tendency has been to employ dampers. The ?dancing? of conductors is then discussed. This is not a very frequent occurrence, and - there is consequent difficulty in formulating mitigative measures.