Impact of Thermal Stresses on the End of Life of Overhead Transmission Conductors

The majority of high-voltage transmission lines use aluminum conductor steel-reinforced conductors, which can be operated continuously at temperatures up to 93°C. Beyond this temperature, the aluminum strands begin to anneal over time and lose mechanical strength and thus, the original safety factors on tensile loading may be compromised. In this paper, the effect of operating electrical conductors at high temperatures on the conductors' end-of-life is investigated. As part of a large conductor expert system, the tensile failure probability is determined by solving the limit-state equation of the conductor subjected to environmental and operational conditions, using Monte Carlo simulations. The integration of the thermal model with the conductor expert system provides asset managers and operators with a complete spatiotemporal view of the aging state of the conductor system, bringing a whole new dimension to effective transmissions asset management, for scheduling of line maintenance and replacement, and for planning future transmission systems.