Statistics for In this paper, a fast method of evaluating the transient stability of power systems using a topological energy function is presented. This is applicable to the case when the load buses are uncoupled and for a class of nonlinear voltage dependent loads. A topological energy function (TEF), using centre of angle (COA) formulation, is used for computation of the stability region. A power Invariant transformation is presented which leads to the decoupling of load buses in a practical system with connected load buses. Although the load characteristics do not remain invariant under this transformation, approximations can be introduced to facilitate the analysis. A numerical example is precentod to illustrate the application of the method. © 1986 by Hemisphere Publishing Corporation.