On-line security of an electric power system using a transient stability contingency screening and ranking technique

In this paper a three-step technique is presented for on-line contingency screening, ranking and transient stability assessment based on a hybrid method. This efficient and robust approach combines the advantages of the time domain integration schemes to compute the initial system trajectory with the equal area criterion. The computer programs developed by the authors were integrated in the software package TRANsySTEM. In order to validate the established mathematical models as well as the software package, the transient stability of the New England test power network was studied. The results obtained with the hybrid formulation were compared with the solutions produced by a time domain simulation program and show a very close agreement. Consequently, the proposed technique classifies correctly, without any dangerous diagnostic or false alarm, all the analysed situations. In addition, this approach provides the transient stability margins as well as the critical machines of the severe contingencies, therefore enabling further design of corrective security actions. Finally, some conclusions that provide a valuable contribution to the understanding of the transient stability assessment of a multimachine power system are pointed out.