Northeast blackout of 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, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Pennsylvania, 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 human error that happened days before the blackout. Maintenance personnel incorrectly set a protective relay on one of the transmission lines between the Niagara generating station Sir Adam Beck Station No. 2 in Queenston, Ontario. The safety relay, which was to trip if the current exceeded the capacity of the transmission line, was set too low.
As was common on a cold November evening, power for heating, lighting and cooking was pushing the electrical system to near its peak capacity. Transmission lines heading into Southern Ontario were heavily loaded. At 5:16 p.m. Eastern Time, a small surge of power originating from the Robert Moses generating plant in Lewiston, New York caused the improperly set relay to trip at far below the line's rated capacity, 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 designed to protect the line from overload, tripped, isolating Beck Station from all of Southern Ontario.
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