Power System Transient Stability Indexes for On-Line Analysis of "Worst-Case" Dynamic Contingencies

The need for on-line analysis of power systems stability vis-a-vis postulated disturbances is felt more than ever before in modern energy control centers. The lack of a general practically implementable analytical method, makes it necessary to consider special classes of contingencies each with its own particular a priori characterization amenable to on-line analysis. In this paper a particular class of disturbances, namely faults near generator terminals, are considered; these are regarded to be "worst-case" conditions. The effects of breaker operation and the load model are taken into account. Two stability indexes are defined depending on the load model. Their computation for individual faults involves evaluation of straightforward algebraic expressions and is thus extremely fast. Simulation results are presented which demonstrate the discrimination capability of the indexes and the validity of the overall approach.