Fuzzy-set based contingency ranking [power system security]

An approach based on fuzzy set theory is developed for contingency ranking of the Taiwan power system. In the proposed approach, the post-contingent quantities are first expressed in a fuzzy set notation. The heuristic rules used by system operators in contingency ranking are then compiled and coded in the form of fuzzy reasoning rules. These reasoning rules form the basis for combining the evidence from each post-contingent quantity and reaching the overall system severity index. Since the set of severe contingency cases have been derived based on operators past experience, it is expected that they will match the human expert´s judgments on what contingency cases are severe. The proposed fuzzy set approach has been applied to contingency ranking of the Taiwan power system which consists of 170 buses, 121 power lines, and 86 transformers