Safe Ratings for Overhead Line Conductors

Many factors must be considered in establishing safe ratings for overhead copper line conductors. Most important is the low-temperature annealing and loss of strength of the hard-drawn copper itself. Others are the effect of atmospheric conditions and line location relative to structures and topographical features tending to obstruct the wind. The actual construction details of the line, such as ground clearances, conductor splices, and connectors are pertinent, as are the policies of the personnel responsible for maintaining the line. This paper attempts to show how these factors can be evaluated to establish operating ratings, indicating how readily available data can be utilized, pointing out the lack of completely satisfactory data on other points. Procedure is stressed rather than results, as the influence of local conditions upon many of the factors precludes publication of ratings which are entirely safe to apply without careful investigation of the effect upon the particular copper conductors to which they are to be applied.