Cost-Benefit for HV Transmission Line Renovation and Replacement Based on Failure Probability and Risk-Based Maintenance

Abstract

In this paper, the innovative method for cost-benefit analysis with risk-based maintenance cost and strategies for renovation and replacement of aged HV overhead transmission line (OHL) in Thailand is proposed. In the analysis, a transmission usage risk involving with renovation and importance index are concerned together with maintenance costs in order to calculate a risk-based maintenance cost. This cost comprises cost of replaced component, maintenance cost, reputation cost and cost of loss of selling electricity. The renovation index is computed from practical scientific quantitative test results and visual inspection while the importance index is computed from the criteria such as percentage loading, system usage, voltage level, contingency, failure record, age, human impact, pollution, public image of individual OHL; and finally those indices are plotted in a risk matrix. The maintenance tasks are suggested for different risk level; however, the risk-based maintenance cost is further compared with the new investment cost to determine a breakeven point for replacing the old line by the new one. Twenty OHLs in Thailand were analyzed in this paper. The results show that five OHLs with high risk and the age is over than 35 years should be planned for a new line while the others be proper maintained according to risk-based maintenance strategy. This innovative method can effectively help transmission utility making decision on transmission maintenance planning.