The outage on Atel's 380 kV power line over the Lukmanierpass happened at around three in the morning, caused by a flashover to a tree in the Brunnen area (canton Schwyz). Atel immediately took all measures necessary to limit the effects of the outage. Power line outages like this are nothing unusual and do occur from time to time. In view of Italy's heavy electricity imports, it is vital for all grid operators to coordinate rapidly and execute the correct responses. Such action was evidently not effective enough in this case: around half an hour after the Atel line outage, a second power line in Misox overloaded and shut down. According to our information, two power lines from France into Italy were interrupted at almost the same time. Afterwards, all power lines to Italy became cut off in a cascade of failures. The exact technical sequence of events and their possible causes are the subject of detailed investigations.
Aare-Tessin Ltd. for Electricity Corporate Communications