At 5:16:11 p.m. on November 9, 1965, a backup protective relay at the Sir Adam Beck No. 2 hydroelectric plant, on the Ontario side of the Niagara River, did what it had been set to do. It tripped the circuit breaker on one of five 230-kilovolt lines carrying power north to Toronto.
The power on that line shifted onto the other four. Each was now loaded past the level its own relay was set for, and they tripped one after another in about two and a half seconds. Roughly 1,500 megawatts that had been serving Canadian loads reversed and was thrown onto the lines running south and east into New York State. Those broke apart too. Within four seconds, the interconnected systems of the region, known as CANUSE, had split into four isolated pieces.
In New York City, the load on Consolidated Edison’s generators jumped by 600 to 800 megawatts, then past 1,000. The industry’s operating guide told an operator that in a disturbance “a prime consideration is to maintain parallel operation throughout the interconnected system if at all possible.” There were no standing instructions saying at what point to cut the ties or drop part of the city to save the rest. The operator on duty, the Federal Power Commission later found, “did not make an immediate clear-cut decision.” Con Edison went down at 5:28 p.m. Most of lower New England and southern New York was dark about 12 minutes after the first relay moved.
The outage covered 80,000 square miles and directly affected an estimated 30 million people in the United States and Canada. In some places it lasted more than half a day.
Finding the cause was harder. An outage usually leaves something burnt or broken behind. Every system checked its equipment, and no faulty equipment was found. It was the early morning of November 15 before the Commission’s experts, working from the companies’ recording charts, traced the start to Beck.
The relay had been set in 1963 to operate at about 375 megawatts. Back then, the load on the lines north out of Beck was much lower. Since then, outages at a new Ontario steam plant had pushed up imports from the United States, and the winter peak was approaching. That evening, the average flow on the first line was 356 megawatts. Normal moment-to-moment fluctuation covered the rest. Ontario Hydro’s officials told the Commission that the people operating their system “were not aware” of the 375-megawatt setting.
By the time the Commission reported to President Johnson on December 6, Ontario Hydro had already taken measures so the same relays could not trigger another failure. The report put it plainly: “the risk of a precise repetition of the power failure is not the main point.” The basic question was whether “other previously unanticipated malfunctions” could set off a similar cascade. In hindsight, the Commission wrote, timely load shedding in parts of New York “might have avoided a city-wide blackout.” It asked every utility to reexamine how its system was designed and run, and called for stronger transmission networks and more coordinated planning between systems. It called the chance of a recurrence “remote.”
In June 1968, according to NERC’s own timeline, the electricity industry set up the National Electric Reliability Council, in response to the 1965 blackout and on the Commission’s recommendation.