The 2003 Italy blackout was a serious power outage that affected all of the Italian Peninsula for 12 hours and part of Switzerland near Geneva for 3 hours on 28 September 2003. It was the largest blackout in the series of blackouts in 2003, involving about 56 million people. Causes Power went off at about 03:20 local time on 28 September 2003. Initial reports from Italy's electricity supplier, GRTN, stated that at the power line which supplied electricity to Italy from Switzerland two trees are falling on the line near the town of Brunnen, causing it to trip; and also that the two 400 kV power lines between France and Italy tripped due to sudden increased demand from those two power lines. Later, it has been shown that the trip of the first line from Switzerland - the so-called "Lukmanier" line - was caused by a tree flashover in Switzerland. The flashover was due to sagging of the conductor as the line was heavily loaded. The cascading effect disrupted power flow to Italy from the two main exporting countries France and Switzerland. GRTN lost control of the grid in the next 4 seconds, with the lines to neighbouring countries tripped one by one amid the cascading effect. Swiss electricity company ATEL later concurred that a power line between Switzerland and Italy went out for a few hours. Frequency dropped down to 49 Hz, due to the loss of import power. Within the next 2.5 minutes, frequency went further down until the under-frequency threshold of 47.5 Hz was hit and all generators were tripped according to the under-frequency protection settings. The reason for the blackout was that during this phase the under-voltage load shedding (UVLS) could not compensate the additional loss of generation, when ca. 7.5 GW of distributed power plants tripped during under-frequency operation (cf. figure "Frequency behavior in Italy in the transitory period", UCTE report, April 2004, p. 115). Effects The night of 27 September 2003 is the night of the annual overnight Nuit Blanche in Rome, Thus, many people were on the streets and all public transportation were still operating at the time of the blackout (at about 3:00 on 28 September 2003) despite the fact that it was very late at night. The blackout caused the carnival to end early. Several hundred people were trapped in metro trains. Coupled with heavy rain at the time, many people