Improved Calculation of Sag for a Conductor Supported at Unequal Heights

Abstract

The sag of conductors of an overhead line is determined from the horizontal tension at the lowest point of the conductors. In a conductor supported at unequal heights the lowest point is calculated, together with the horizontal tension, from hyperbolic expressions using an iterative procedure. In practice the hyperbolic functions are usually approximated by their first two terms. While the results are close to the actual values some differences may arise because the approximate methods may not converge to the exact values. The Newton Raphson sag method presented in the paper applies the Newton Raphson method to obtain fast convergence to the exact values. It is inherently more accurate than the classical iterative procedure based on approximating the hyperbolic functions; and the convergence criterion may be set as small as required. The method is also applicable to a conductor supported at equal heights.