A new snow and ice load map for mechanical design of power lines in Great Britain

• Cylindrical ice accretion models are used to analyse power line ice loads in the UK.
• We estimate return levels of wet snow loads at 131 weather station locations.
• Rime icing is simulated with a high resolution numerical weather prediction model.
• The highest ice loads are expected in the wettest parts of the Scottish highlands.
• The final results are interpolated to a map of 500 m resolution.

A new high resolution map of extreme snow and ice loads has been produced. Wet snow accumulations on overhead power lines are estimated using observations from a network of surface synoptic weather stations, while areas of severe in-cloud icing (rime icing) are identified from high resolution numerical weather prediction model simulations. Ice loads at 50 year return period were estimated using the “Peaks-Over-Threshold” (POT) method and interpolated to a high resolution map using regression kriging. The results indicate a significant variation with elevation and latitude, with the highest loads expected in the wettest parts of the Scottish Highlands. In-cloud icing occurs mainly above 300–400 m and is the dominant icing type above 400–600 m depending on the location. The final icing map demonstrates how state of the art atmospheric icing models can be successfully utilized to estimate the icing climate even when only very limited measurements of actual icing are available.