A RELIABILITY APPROACH TO TRANSMISSION EXPANSION PLANNING USING FUZZYFAULT-TREE MODEL

In this paper, a fuzzy fault-toe based reliability analysis of an opti mally planned transmission system is presented. A fault-tree is constr ucted using system minimal cuts. Fuzzy top event probabilities are cal culated using trapezoidal nature fuzziness of primary events. In part- I, system minimal cuts up to third order containing line components ar e determined based on the condition that the system fails if a load bu s fails. To establish the rank of the components and cut sets, the rel iability improvement index (RII) is calculated by preventing the failu re of each component and cut set separately. To establish the degree o f sensitivity of components, the sensitivity index is calculated based on the change of the top event probability caused by the change of fu zziness of failure probability of each component. In part-II, system m inimal cuts up to first order which contain lines only are determined based on the criteria that (a), the system fails if overload occurs in a line or bus voltage variation is more than +/-11% and (b), the syst em fails if overloading in a line and bus voltage variation more than +/-11% occur simultaneously. Finally, a maximum reliable configuration is derived for the said criterion by adding lines step by step in the routes with the highest positive RII value. (C) 1998 Elsevier Science S.A. All rights reserved.