Islanding Operation During the 2019 Alto Adige Snowstorm Emergency

The paper describes the events that led, in November 2019, to a local blackout in Trentino-Alto Adige (Northern Italy). The events were caused by a heavy snowstorm that resulted in about 7000 faults on the electric system for short-circuits, trees falling on electrical lines etc. In consequence, a 132 kV portion of the grid, and the underlying MV/LV distribution grid, remained isolated from the national transmission grid a part of the 132 kV power system. Overall, approximately 25 thousand customers were involved in a local blackout for more than 24 hours. However, the blackout has been mitigated by the attempts of operating the local system as an electric island, exploiting the black start capability of hydro power plants with enough power capacity to supply the island resulting from the disconnection. The paper describes the main features of the island operation, the main problems encountered until the final restoration, the lessons learned and provides a set of suggestions in order to mitigate the effects of such heavy weather phenomena in the future.