It was an outage that affected nearly 55 million people, including 10 million in Ontario, for hours, days or even a week in some cases. It caused the loss of nearly 19 million hours of work in Ontario alone, a $2.3-billion drop in manufacturing deliveries, and a 0.7% decline in Canadian GDP in single month.
The U.S. and Canadian governments created the joint U.S.–Canada Power Outage Task Force, with a mandate to study the events and make recommendations with a view to avoiding another economic catastrophe of that scope. The Task Force made a total of 46 recommendations, several of which have been implemented across North America.
The sequence of events in the outage
It all started around 12:15 p.m., when data from the grid serving the area around Cleveland-Akron, Ohio was suddenly no longer available to transmission system operators, who thus unknowingly found themselves operating their systems with erroneous data.
At 1:31 p.m., a unit tripped at Eastlake Power Plant, in a suburb of Cleveland, resulting in a loss of 600 MW on the system and consequently the loss of a large amount of reactive power compensation. This disrupted the generation/load balance, putting the system in a precarious situation, unbeknownst to the operators.
Around 2:15 p.m., a computerized alarm system failure, lasting a good part of the afternoon, meant that system operators were not alerted to the situation.
At 3:05 p.m., three 345-kV lines tripped and reclosed several times, as nearby tree branches came into contact with the conductors. At 3:46 p.m., when the alarm system came back up, operators saw that the system had deteriorated and reliability was threatened. The same 345-kV lines tripped again and did not reclose this time, overloading 138-kV lines, which tripped in cascade. In all, sixteen 138-kV lines were tripped out of service. According to the conclusions of the U.S.–Canada Outage Task Force, the operators could have taken action at this point, by initiating wide-scale load shedding to restore the generation/load balance.
At 4:05 p.m., a fourth 345-kV line in northern Ohio tripped. Within eight minutes, over 55 million people were without electricity.
Causes of the outage
This situation could have been avoided, or at least attenuated. The Task Force reported that there were a number of contributing factors to the outage:
- A lack of planning and inadequate understanding of the state of deterioration
- Insufficient diagnostic support
- Poor vegetation control
- Vulnerable computer systems
- Unclear and non-mandatory reliability standards
Consequently, its report made recommendations on every aspect of reliability of the Bulk Electric System.
Implementation of the mandatory standards regime
One of the report’s main recommendations was to make the North American Electric Reliability Corporation (NERC) reliability standards mandatory in the United States and Canada. The governments of both countries moved quickly to pass laws on power system reliability. In Québec, the National Assembly adopted Bill 52 modifying the Act respecting the Régie de l’énergie making entities in Québec subject to the reliability standards adopted by Régie de l’énergie.
Impact of NERC standards
In November 2004, NERC published a first version of its reliability standards (known as Version 0), which included operating policies, planning standards and compliance requirements. They were adopted in February 2005. On June 18, 2007, the reliability standards became mandatory in the United States.
Examples of standards with positive impact
- Standard FAC-003 requires each entity to develop and implement a vegetation management program. If incidents caused by vegetation are too frequent or have extensive repercussions here or elsewhere, the Régie de l’énergie could impose financial sanctions or a remedial plan.
- Standard EOP-008 deals with emergency plans for loss of control centre functionality. Each entity must ensure that any system operation activities that could have an effect on the reliability of the generation and transmission system will be maintained at all times.