Environmental Criteria For The Selection Of Underground Transmission Cable Conductors

The results of major LCA studies show that under the assumption of European power mix, power losses dominate the cable impacts in nearly all categories, contributing with up to 96% to climate change for example. Therefore, it is relevant to focus primarily on the reduction of losses. Dealing with underground cable systems, it is essential to properly select the conductor for the expected service in the grid, because the metal core determines the amount of losses during the lifespan of the power link. Based on the scenario of a typical French underground circuit, the paper presents the calculations of cable losses, and illustrates a method to assess the optimal economic conductor taking into account the entire life span of the system, leading also to the best environmental solution with minimised losses. The French TSO has been developing models and methodology over the last decade in order to perform LCA on transmission systems. Leading the Cigre Working Group B1.36 [8], RTE has contributed to establish in 2015 a methodology dedicated to LCA for underground cables. In addition, a case study was carried out. This significant work allows the transmission system operators to identify the main environmental impacts of underground cables, their sources, as well as improvement targets. Electricity losses are identified as responsible for the main impacts (climate change for instance), while the extraction and the manufacturing phase of the metal components represent the outlines of mineral depletion impact. To overcome those environmental issues, different alternatives have to be compared, both to reduce losses and the mineral depletion. The study field needs to be extended to a more global scope, in order to integrate the whole benefits of the grid. The authors review and discuss their approach, results and works in progress within their company, with a common aim of the improvement of energy efficiency.