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4.6.5. Adapting overhead lines to increasing temperatures

Electric transmission and distribution network providers in the United Kingdom face increasing risks from heat waves, which pose a threat to their power infrastructure. Thermal expansion can cause power lines to sag, hence their clearance from land can become a danger to the general public. Sagging may also result in contact with trees and other structures, and hence in electrocution or fires. Furthermore, the electrical current that passes through overhead power lines must be reduced under high ambient temperatures to prevent the overheating of equipment. Finally, warmer power lines can result in decreased efficiency due to a process known as de-rating. All of these impacts ultimately result in risks of accidents, power cuts and revenue losses, as well as cascading network failures.

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Western Power Distribution (WPD) is a large electric utility in the United Kingdom. WPD cooperated with the Energy Network Association (ENA) in order to operationalise adaptation measures in its infrastructure. Such adaptation measures included increasing the height of poles supporting power lines, installing conductors with hotter operating limits and implementing the use of ‘low-sag’ conductors. The most cost-effective measure identified was to increase the minimum design temperature of new overhead lines, which would require increasing the design height of wood poles by 0.5 metres. This adaptation accommodates the projected increases in sagging without exceeding legal limits on the height of overhead lines. Moreover, WPD participated in a project that updated the UK Distribution Industry’s understanding of conductor ratings for overhead lines. This projected is expected to lead to an update of national standards. Finally, WPD and various other UK energy companies are also developing a software tool that will allow UK energy companies to optimise their overhead line ratings.

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Cooperation among relevant institutions turns out to be the major enabling factor for this initiative. Members of electricity network operators have been brought together with government and regulating agencies in the ENA-led Climate Change Adaptation Task Group. The Task Group yields approaches to identify impacts of climate change on electricity TSO and DSO networks, and to develop and select cost-effective and efficient adaptation measures.

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