A NEW CONTINGENCE Y RANKING METHOD BASED ON FUZZY-SET THEORY

This paper presents a new approach for power system contingency ranking based on fuzzy-set theory. It is best known that human experts and system operators, past experience are important basis in security evaluation of any power system Since, these experts and experiences usually use linguistic variables, uncertainty and imprecision exists in knowledge representation. However, it is possible to transform these linguistic variables to fuzzy-set theory concepts. Initially those contingencies that will cause loss-of-load, loss-of-generation, or islanding are first identified. Then, after computing of post - contingent quantities ( fine flows, bus voltages ) for other possible contingencies by 1P-1Q iteration of FDLF, a severity value is introduced for each post-contingent quantity upon human experts and operators' experience. These values play the role of membership functions for any linguistic variable. A set of fuzzy reasoning rules duo to operators' heuristic rules is used to construct an Intelligent Computation Unit (ICU) to generate the severity indices of contingencies This method is shown to be much faster and more precise than ealier proposed fuzzy reasoning approach [1].