The Northeast blackout of 2003 was a widespread power outage throughout parts of the Northeastern and Midwestern United States, and most parts of the Canadian province of Ontario on Thursday, August 14, 2003, beginning just after 4:10 p.m. EDT.
Most places restored power by midnight (within 7 hours), some as early as 6 p.m. on August 14 (within 2 hours), while the New York City Subway resumed limited services around 8 p.m. Full power was restored to New York City and parts of Toronto on August 16. At the time, it was the world's second most widespread blackout in history, after the 1999 Southern Brazil blackout. The outage, which was much more widespread than the Northeast blackout of 1965, affected an estimated 55 million people, including 10 million people in southern and central Ontario and 45 million people in eight U.S. states.
The blackout was due to a software bug in the alarm system at the control room of FirstEnergy, which rendered operators unaware of the need to redistribute load after overloaded transmission lines dropped in voltage. What should have been a manageable local blackout cascaded into the collapse of much of the Northeast regional electricity distribution system.
According to the New York Independent System Operator (NYISO)—the ISO, responsible for managing the New York state power grid—a 3,500 megawatt power surge (towards Ontario) affected the transmission grid at 4:10:39 p.m. EDT.
For the next 30 minutes, until 4:40 p.m. EDT, outages were reported in parts of Michigan (Detroit), Ohio (Cleveland, Akron, Toledo), Ontario (Toronto, Hamilton, London, Windsor), New Jersey (Newark), and New York (New York City, Suffolk, Nassau, Westchester, Orange and Rockland counties, Rochester, Syracuse, Binghamton, Albany).
This was followed by outages in other areas initially unaffected, including all of New York City, portions of southern New York state, New Jersey, Vermont, Connecticut, as well as most of the province of Ontario. Eventually, a large, somewhat triangular area bounded by Lansing, Michigan, Sault Ste. Marie, Ontario, the shore of James Bay, Ottawa, New York, and Toledo was left without power.
According to the official analysis of the blackout prepared by the US and Canadian governments, more than 508 generating units at 265 power plants shut down during the outage. In the minutes before the event, the NYISO-managed power system was carrying 28,700 MW of load. At the height of the outage, the load had dropped to 5,716 MW, a loss of 80%.
Essential services remained in operation in some of these areas. In others, backup generation systems failed. Telephone networks generally remained operational, but the increased demand triggered by the blackout left some circuits overloaded. Water systems in several cities lost pressure, forcing boil-water advisories to be put into effect. Cellular service was interrupted as mobile networks were overloaded with the increase in volume of calls. Multiple cell sites were out of commission due to power outages. Television and radio stations remained on the air, with the help of backup generators, although some stations were knocked off the air for periods ranging from several hours to the length of the entire blackout.
High heat played a role in the initial event that triggered the wider power outage. Much of the affected region reached temperatures higher than 31 °C (88 °F) that day, increasing energy demand as people across the region turned on fans and air conditioning. This caused the power lines to sag as higher currents heated the lines.
Most of the Amtrak Northeast Corridor service was interrupted, as it relied on electricity for its signaling and crossing systems; electrified commuter railways also shut down. Via Rail in Canada was able to continue most of its service. All airports in the affected area closed immediately, there were no departures, and incoming flights had to be diverted to airports with power.
The reliability of the electrical grid was called into question and required substantial investment to repair its shortcomings.
In areas where power remained off after nightfall, the Milky Way and orbiting artificial satellites became visible to the naked eye in metropolitan areas where they cannot ordinarily be seen due to light pollution.
Most places restored power by midnight, as early as 6 p.m. on August 14, and the New York City Subway had resumed limited services around 8 p.m. Some areas lost power for only four to eight hours; these are: Albany and parts of Long Island in New York; three‐quarters of New Jersey; parts of Pennsylvania, Ohio and Michigan; New London County, Connecticut; parts of downtown Toronto, Mississauga, and London in Ontario; portions of western Ottawa in Ontario, including Kanata and south to Kingston; a number of areas of the Regional Municipality of Niagara in Ontario; and parts of Southwestern Ontario, particularly areas near the Bruce Nuclear Generating Station.
By the next morning (August 15), some areas of Manhattan regained power around 5:00 a.m.; Staten Island regained power around 3:00 a.m. Half of the affected portions of Ontario regained power by the morning. By early evening of August 15, two airports, Cleveland Hopkins International Airport and Toronto Pearson International Airport, were back in service. By August 16, power was fully restored in New York and parts of Toronto. 500,000 Detroit Edison customers were still without power at 10:00pm August 15; all were restored by 6:30am August 16.
Within the area affected, about 200,000 people continued to have power—in the Niagara Peninsula of Ontario; the easternmost corner of Ontario (centered on Cornwall); northwestern Ontario (west of Wawa); and the Buffalo, New York area, excluding southern Erie county, along the shore of Lake Huron via a feeder line to Owen Sound from Bruce Nuclear Generating Station. Three of the four Bruce B units were able to throttle back their output without a complete shutdown, then reconnect to the grid within five hours: the portion of New York state including parts of Albany and north and west of Albany, a small pocket of mid-east Michigan, the Upper Peninsula of Michigan, and small pockets in New Jersey. The unaffected area was protected by transmission circuit devices at the Sir Adam Beck Hydroelectric Generating Stations in Niagara Falls (coincidentally, the starting point of the Northeast blackout of 1965) at a switching station of the hydroelectric power station in Cornwall, as well as central New York state. Philadelphia and the surrounding mid-Atlantic areas were also completely unaffected because PJM disconnected them. The Saint Clair power plant in East China Township, Michigan, remained online for about 36 hours, and residents were informed that the plant would have to shut down in order to facilitate the reboot of the whole system. Orrville, Ohio, was able to restore power within an hour disconnecting the local utility from the larger grid and restarting the coal-fired generator.
Power grid management concepts
The load on any power network must be immediately matched by its supply and its ability to transmit that power. Any overload of a power line or generator can cause costly damage, so the affected device is disconnected from the network if an overload is detected.
The electrical resistance of a power line causes it to produce more heat as the current it carries increases. If this heat is not sufficiently dissipated, the metal conductor in the line will expand and lengthen, so that it sags between supporting structures. If the line sags too low, a flash over to nearby objects (such as trees) may occur, causing a transient increase in current. Automatic protective relays detect the excessively high current and quickly disconnect the line, so the load previously carried by the line is transferred to other lines. If the other lines do not have enough spare capacity to accommodate the extra current, their overload protection will react as well, causing a cascading failure.