Practical design of transmission line tensions

PRECISE CALCULATIONS are seldom justified in the determination of the sags and the tensions of transmission lines, because the effect of many of the variables bearing on tension are indeterminate: no practical equation exactly describes a suspended cable; the conditions of conductor loading are, of necessity, idealized; the elastic properties of conductors are not constant; and additional errors are inevitable during construction. However, the catenary is taken as the form assumed by a suspended cable, the equation of which is
$y=C\ {\rm cosh}{x\over C}$
.