This paper proposes a two-stage methodology for online identification of power system dynamic signature using phasor measurement unit (PMU) measurements and data mining. Only transient stability status is usually predicted in the literature to assist with corrective control, without the dynamic behavior of generators in the event of instability. This paper uses traditional binary classification to identify transient stability in the first stage, and then develops a novel methodology to predict the nature of unstable dynamic behavior in the second stage. The method firstly applies hierarchical clustering to define patterns of unstable dynamic be-
havior of generators, and then applies different multiclass classification techniques, including decision tree, ensemble decision tree and multiclass support vector machine to identify characterized unstable responses. The proposed methodology is demonstrated on a multi-area transmission test system. High prediction accuracy at both stages of identification is demonstrated.Index Terms-Corrective control, data mining, decision tree, ensemble, hierarchical clustering, phasor measurement units, power system dynamic signature, support vector machine, transient stability.Tingyan Guo (S'11) received the B.Eng degree in electrical and electronic engineering from the University of Manchester, Manchester, U.K., in 2011. She is currently working towards the Ph.D. degree at the same institution. Jovica V. Milanović (M'95-SM'98-F'10) received the Dipl.Ing. and M.Sc. degrees from