A fault tree is constructed with the help of failure modes of different components of thegas power plant. And, an expression is obtained for evaluating the probability of failure of thisplant using minimal cut set approach. All the failure probabilities are represented as intervalvalued trapezoidal vague set due to uncertainty in the collected data and accordingly fuzzyreliability of the system is evaluated using interval valued vague sets arithmetic operations. Themajor advantage of using interval valued vague sets, over fuzzy sets and vague sets, is thatinterval valued vague sets separate the positive and negative evidence for the membership of an
element in a set and also the values of the membership and non-membership of an element in aset are intervals instead of a single real number. By using this approach fuzzy system reliabilitycan be analyzed in a more flexible and more intelligent manner.