Sag calculations for suspended wires

The method here described for calculating sags, and strains in suspended wires was devised to shorten the process of the transmission line computations, especially where the effect of temperature is to be considered. The method is a semi-graphical one and involves no numerical operations other than may be performed by the simplest slide rule manipulation. The method is based on the assumption that the suspended conductor conforms to the catenary, which is generally considered to be the actual fact, although as far as the writer is informed no scientifically accurate verification on a large scale under practical conditions has been attempted. The results obtained by the use of the catenary basis will not differ from those derived from the usual parabola formulae more than 10 per cent in the strain for a sag of 7.5 per cent. For larger sags, however, the difference rapidly increases. A description of the use of the method will be given, followed by a brief statement of the mathematical justification therefor.