Torque-Angle Characteristics of Synchronous Machines Following System Disturbances

A method of predetermining the torque-angle characteristic of a synchronous machine following a system disturbance is of importance in calculating the transient stability limit and in evaluating the effect on this limit of additional rotor circuits or of a change in excitation. In the first part of this paper equations are derived which are of sufficient generality to evaluate such factors. Two types of system disturbances are considered: 1. Switching in or out of a connecting line, 2. Occurrence of a balanced three-phase system fault. In the second part, an actual case of switching out a connecting line is calculated and the results compared with field tests taken on the New York Power and Light Corporation´s system. No attempt has been made to draw any general conclusions as to the effect of amortisseurs or changes in excitation. A subsequent paper will present results which have been obtained from the application of the method presented in this paper.