Apparent impedance correlation of transient energy margin and time simulation

A procedure was developed to relate the transient energy margin of a multimachine power system to the apparent impedance of a line protected by an out-of-step relay. In this procedure, only the multimachine system parameters are used, and the conventional intermediate step of forming a two-machine equivalent is eliminated. A technique for generating the swing impedance locus is described. The method is tested for a loss of generation disturbance on a 23-generator equivalent of the Florida Power & Light Co. network. The results obtained are compared with time simulation results