To make power network planning and decision-making of operation and maintenance more scientific

a method for estimating optimal economic life interval of transmission line based on minimum annual average cost of life cycle is proposed. The method considers not only the enlistment age

but also climate

natural disaster

geographical and external forces

components

civil work

operation and maintenance as influencing factors on the failure rate of transmission lines. The least squares support vector machine (LS-SVM) is then adopted to calculate the failure rates of ordinary failure

large failure and catastrophic failure to make calculated results more credible. In addition

this method uses the theory of interval analysis to calculate different costs of transmission lines

which successfully eliminates the error of cost calculation due to simplex setting value. In the end

a case study proves the effectiveness of the proposed method in evaluating optimal economic life interval of transmission lines

and points out the guidance effect of the evaluation results on power network planning and decision-making of operation and maintenance. This work is supported by National Natural Science Foundation of China (No. 51107112).