Condition assessment and failure probability of existing transmission lines

Thousands of transmission lines built in North America over the last 115 years are still serving beyond their original design life. To establish an efficient refurbishment program for those lines, it is imperative to evaluate their damage states and failure probabilities. In this paper, a fuzzy weighted average technique is proposed and integrated into the failure probability. For damage assessment corrosion rate is assumed to be a time-invariant random variable. Since the failure probability has no exact solution, an approximate solution using Edgeworth series which allow the failure probability to be expressed in terms of the first four moments of the cumulative distribution function of the safety margin is proposed. A computer program was developed to calculate the damage states and the failure probabilities of existing transmission lines. The proposed method is expected to improve effectiveness of transmission lines maintenance and refurbishment programs. A case study is presented.