Panne de courant nord-américaine de 1965

The northeast blackout of 1965 was a significant disruption in the supply of electricity on Tuesday, November 9, 1965, affecting parts of Ontario in Canada and Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont in the United States. Over 30 million people and 80,000 square miles (207,000 km2) were left without electricity for up to 13 hours. The cause of the failure was the setting of a protective relay on one of the transmission lines from the Sir Adam Beck Hydroelectric Power Station No. 2 in Queenston, Ontario, near Niagara Falls. The safety relay was set to trip if other protective equipment deeper within the Ontario Hydro system failed to operate properly. On a particularly cold November evening, power demands for heating, lighting, and cooking were pushing the electrical system to near its peak capacity. Transmission lines heading into southern Ontario were heavily loaded. The safety relay had been misprogrammed, and it did what it had been asked to do: to disconnect under the loads it perceived. As a result, at 5:16 p.m. Eastern Time, a small variation of power originating from the Robert Moses generating plant in Lewiston, New York caused the relay to trip, disabling a main power line heading into Southern Ontario. Instantly, the power that was flowing on the tripped line transferred to the other lines, causing them to become overloaded. Their own protective relays, which are also designed to protect the lines from overload, tripped, isolating Beck Station from all of southern Ontario. With nowhere else to go, the excess power from Beck Station then flowed east, over the interconnected lines into New York state, overloading them as well, and isolating the power generated in the Niagara region from the rest of the interconnected grid. The Beck generators, with no outlet for their power, were automatically shut down to prevent damage. The Robert Moses Niagara Power Plant continued to generate power, which supplied Niagara Mohawk Power Corporation customers in the metropolitan areas of Buffalo and Niagara Falls, New York.