Critical weather conditions such as the 1998 Ice Storm that hit the north east of the American continent resulted in the failure of many distribution lines, leaving a great percentage of the population without service for up to a month. Such events highlight the need to reconsider the design of overhead distribution lines. Currently, distribution line structures are built according to deterministic design criteria that is not optimal and does not reflect variability in environmental conditions as a function of location. This paper examines the use of probabilistic methods to evaluate the structural strength of a typical medium voltage line under wind and ice loads. Since the principal component of the line is the wood pole, only failure modes associated with failure of poles are presently considered. The methodology consists in establishing a failure model of the line based on strategic poles (end and angle poles) and intermediate poles, and estimating the structural reliability of typical poles with Monte Carlo simulations. For the location considered in the study, the analysis indicates a strong dependency of reliability estimates on wind loads alone and cobmined ice and wind loads. The effects of span length and wood pole deterioration on reliability are also investigated.
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