Damage assessment and soft reliability evaluation of existing transmission lines

This paper introduces a methodology for reliability assessment of existing-transmission structures and lines in the presence of structural deterioration. A model for damage assessment of existing-transmission structures is proposed. The model uses fuzzy weighted averages formula (FWA) and utilizes a fuzzy computational technique called resolution identity of fuzzy sets. The damage-state of the structure or line is a fuzzy function that can be used to fuzzily or "soften" the probability of failure of the existing transmission-structure or line. The model for probability of failure is derived as a function of the cumulative distribution of the standardized safety margin and the damage-state of the structure or line. The probability of failure is then expressed in terms of the first four moments of the safety margin probability distribution function. The proposed method produces a realistic reliability assessment of existing structures or line. A numerical example is given.