Northeast Blackout of 1965 - Cause

Cause

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 coming 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 protective relays, which are designed to protect the line from overload, tripped, isolating Beck Station from all of Southern Ontario.

With no place else to go, the excess power from Beck Station then switched direction and headed 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, NY. These areas ended up being isolated from the rest of the Northeast power grid and remained powered up. The Niagara Mohawk Western NY Huntley (Buffalo) and Dunkirk steam plants were knocked offline. Within five minutes, the power distribution system in the Northeast was in chaos as the effects of overloads and loss of generating capacity cascaded through the network, breaking it up into "islands." Station after station experienced load imbalances and automatically shut down. The affected power areas were the Ontario Hydro System, St Lawrence-Oswego, Upstate New York, New England, and Maine. With only limited electrical connection southwards, power to the Southern States was not affected. The only part of the Ontario Hydro System not affected was the Fort Erie area next to Buffalo which was still powered by older 25 Hz generators. Residents in Fort Erie were able to pick up a TV broadcast from New York where a local backup generator was being used for transmission purposes.