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Research and operational activities to cope with wet snow impactson overhead power lines in current and future climate over Italy

pubblicazioni - Memoria

Research and operational activities to cope with wet snow impactson overhead power lines in current and future climate over Italy

Sono stati studiati i cambiamenti di temperatura e precipitazione e le variazioni di alcuni eventi estremi in Italia, sulla base delle più recenti simulazioni climatiche ad elevata risoluzione spaziale. I risultati indicano un inasprimento delle condizioni climatiche nel corso del secolo.

The last heavy wet snowfall in the Abruzzo region (16-18 January 2017) caused serious problems for the safety and operation of the Italian Electric System. During this event, wet snow sleeves on overhead lines reached 15 kg/m in areas where the design criteria did not exceed 5 kg/m. As the frequency and intensity of extreme phenomena have been increasing over the Italian territory in the last 15 years, there is an urgent need for a Climate Change Resilience Planning of the entire electrical system to cope with extreme phenomena and to minimize potential power outages. In operational management, the Transmission and Distribution operators require accurate weather forecasts to alert the areas affected by extreme events and, at the same time, they ask for appropriate information to adopt efficient adaptation actions to increase the resilience of the system.

To this aims RSE has developed the weather forecast system WOLF (Wet-snow Overload aLert and Forecast), based on RAMS, a Numerical Weather Prediction model, and the Makkonen model, a simple cylindrical accretion model for wet snow, to estimate ice loads expected on high and medium voltage national grid. Moreover, on the basis of the forecasted meteorological conditions, the system provides an estimation of the current required to maintain a power line ice-free. Another important request of stakeholders and policy-makers consists of planning properly the future overhead lines, as well as strengthening the existing network by taking into account the snow loads expected in the coming decades over the whole national territory. However the current climate information do not allow to develop an accurate action plan and to integrate it into decision making.

To respond to these needs some wet-snow projections expected in medium term have been elaborated on the basis of the state of art climate models, i.e. 14 EURO-CORDEX simulations at horizontal resolution of 0.11° (about 12 km) under the emission scenario RCP 8.5. The results highlight a wet-snow load increase of about 70-100 % over the Alps, especially in the Northern and Western mountain regions with a good agreement among the models, whereas a decrease of about 20-40 % in the Po valley with a medium confidence. In the Central and Southern Italy the signal has been found weaker (wet-snow is expected to decrease of about 10- 20 %) with low confidence. Larger uncertainties characterize the Central and Northern Apennines where the signal is almost absent and no useful information can be inferred for these areas.

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