The Rayleigh method in network calculations

An approximation method for determining the input impedance of a resistive circuit, or one in which the reactance-resistance ratio is the same for every branch, hence permitting treatment as a resistive circuit, is presented. The method is based on the minimum power-dissipation characteristics of such networks and provides both an upper and a lower bound to the true impedance. It is presented with the view that in certain cases, as in power-system short-circuit calculations where the resistive component may often be neglected, the necessity of evaluating high-order determinants or manipulating star-mesh transformations can be eliminated.