Adapting overhead lines to climate change: Are dynamic ratings the answer?

Thermal ratings of overhead lines (OHL) are determined by the current being carried and ambient climatic conditions. Higher temperatures as a result of climate change will give rise to lower ratings, and thus a reduction in current-carrying capacity across the electricity network. Coupled with demand growth and installation of renewable generation on weaker sections of the network, this could necessitate costly reinforcements and upgrades. Previous UK-based work applying a subset of data from the UK Climate Projections model (UKCP09) has indeed indicated likely reductions in the steady-state OHL ratings under worst-case temperature increases. In the present work, time series data from the full UKCP09 probabilistic climate change modelling framework, including an additional algorithm to incorporate hourly wind conditions, is applied to OHL ratings. Rather than focus purely on worst-case conditions, the potential for an increased risk of exceeding nominal ratings values on thermally constrained OHL is analysed. It is shown that whilst there is a small increase in risk under future climate change scenarios, the overall risk remains low. The model further demonstrates that widespread use of real-time dynamic rating systems are likely to represent the most cost-efficient adaptation method for lines which are frequently thermally constrained.