On the Mechanism of Transient Instability of Power Systems: Improved Results

In recent studies, using energy functions associated with a critical group of machines, transient stability results which are less conservative than other existing results, have been obtained. The existence and identity of a critical group is ascertained in these studies by off-line simulations. In the present paper, we establish stability results for a multi-machine power system with non-uniform damping, and use these to establish the identity of the critical group of machines in a power system due to a given fault. The applicability of the present results in obtaining an estimate of the domain of attraction of an asymptotically stable equilibrium of a power system is demonstrated by means of a specific example.