Further developments of the equal-area criterion for multimachine power systems

An efficient method for determining the transient stability of a multimachine power system is presented. For a given disturbance, the method identifies the critical machine by observing the variation in accelerating power of the severely disturbed machines. The critical machine is considered to be the one which has a tendency to initiate the instability. The transient stability of the system is determined by checking the stability limit of only the critical machine through a modified equal-area criterion. The stability limit or critical situation is diagnosed from the simultaneous occurrence of zero accelerating power and speed of the critical machine in the postfault period. Unlike the previous equal-area criterion method, the proposed method does not require the computation of an unstable equilibrium point. Also, the latter method releases some of the assumptions made in the former method. The proposed method was tested on three power networks and the results obtained were compared with the actual values and those reported previously.