The power grid infrastructure is vulnerable to some extreme meteorological phenomena and this could create some difficulties in the safe management of the power system. The wet-snow accretion on OHL (OverHead Lines) is well-known to the Transmission and Distribution System Operators (TSO&DSO). The problem affects much of Europe, with an annual number of wet-snow type steadily increasing over the total number of snowfalls.

The problem imposes a greater attention to this phenomenon, either through a focused weather forecast both through active and passive mitigation strategies. RSE has developed WOLF (Wet snow Overload aLert and Forecasting) for OHL warning on the transmission power grid. The weather forecast system is already being tested at the Italian TSO.

WOLF together with wet-snow load, provides an estimation of the ant-icing current necessary to keep OHL free of wet-snow sleeve formations, supporting operators in adopting mitigation active strategies. In synergy with WOLF, an automatic station named WILD (Wet Snow – Ice Laboratory Detection) has been installed in the municipality of Vinadio in the west Alps, at an altitude of 950 m asl, for the verification of the forecasts system.

Through WILD measurements, it is possible to analyse in detail the weather conditions most critical for the wet-snow sleeve formation and, at the same time, to make the “tuning” of the parameters in the models of accretion and anti-icing. A prototype of an active anti-icing circuit is able to maintain snow-free the surface of a typical cable in any condition of wet-snowfall and a rotating system allows to measure and compare the sleeve accretion on different type of conductors.

In the terms of the passive mitigation, a qualitative test is being carried out at WILD station on innovative conductors materials provided by Italian TSO, characterized by different surface hydrophobic and ice-phobic treatments. The wet-snow accretions on new cables are compared, although qualitatively, in the same weather conditions with those on conventional conductors. This experimentation may be an important test to get a selection of materials to be used in the areas most exposed at wet-snow risk.