Reliability and security assessment of existing transmission lines using fuzzy set theory

A new method for updating reliability and security of existing transmission lines is introduced. In this method, the uncertainty is divided into objective and subjective parts. The objective part can be processed by probability theory. The subjective part is dealt with by fuzzy set theory. Two fuzzy sets for each subjective factor, one for gravity of the subjective feature and the other for the effect on the event of interest are formed using linear membership functions. Fuzzy intersect is then used to merge the gravity and the effect of each subjective factor. To merge the objective and subjective information, a fuzzy conditional relation is formed and the composition of this relation with the subjective information is made. From the composition, a fuzzifier subset is extracted and the objective information is fuzzified