This paper presents a novel methodology to identify critical contingencies that produce short-term voltage stability problems (STVS). The proposed methodology classifies the state of the pow-er system for each contingency, assessing the voltage stability of the post-contingency dynamic response from the calculation of the maximal Lyapunov expo-nent (MLE) and dynamic voltage indices at each bus and the whole system. In order to determine the crit-ical contingencies, the values of the indices and the results of the classification of the post-contingency state are statistically analysed. The methodology is tested in the New England 39-bus system, obtaining satisfactory results in relation to the identification not only of the most critical contingencies but also of vulnerable buses to voltage instability. New contri-butions of this work are the contingency classifica-tion methodology, the algorithm for calculating dy-namic indices and the method of classification of the operating state as a function of the STVS problem magnitude.
POWER SYSTEM CONTINGENCY RANKING BASED ON SHORT-TERM VOLTAGE STABILITY INDICES