U.S.-Canada Task Force Releases Power Outage Time Line

WASHINGTON, DC, September 12, 2003 (ENS) - One of the characteristics of the August 14 blackout that left some 50 million people in eight states and the Canadian province of Ontario without power was an apparent “voltage collapse” on portions of the transmission system surrounding and within the northern Ohio and eastern Michigan load centers, a task force investigating the incident said today.

The Joint U.S.-Canada Power Outage Task Force released a timeline of events that it says will be instrumental in determining the causes of the widespread outage. The timeline is not intended to explain why the blackout happened or to assign fault, only to provide an early picture of what happened, the task force said.

The task force was appointed by Prime Minister Jean Chretien and President George W. Bush to identify the causes of the power outage and to seek solutions to help prevent future outages.

"Dozens of expert investigators from both countries have been working diligently," U.S. Energy Secretary Spencer Abraham said. "They have interviewed utility and control-center personnel, examined vast amounts of computer data and sifted through thousands of documents to put this timeline together. But we must now arrange and analyze even larger amounts of additional information to lead us to the specific causes."

Canada's Minister of Natural Resources Herb Dhaliwal, co-chair of the task force said, "We have done a preliminary examination of the data. This sequence of events is only a first step in the process of uncovering what has happened on August 14th. To complete its work, the task force will continue to work with all the parties involved to further analyze the data, and come to an understanding of why this has happened."

power station

Power station control rooms across the Northeast, like this one at Niagara Mohawk's Dunkirk power plant, went dark August 14. (Photo by David Parsons courtesy NREL )
The timeline released today outlines significant physical and electrical events that occurred in a narrow window of time, before and during the cascade that led to the blackout. It reviews events beginning at approximately 12 noon EDT on that day, to provide a picture of the sequence of events and how the grid situation evolved over the afternoon.

It focuses chiefly on events that occurred on major transmission facilities of 230 kilovolts and greater and at large power plants.

Input to the sequence of events came from the North American Electric Reliability Council (NERC), Independent System Operators, utility companies and regulatory agencies from both countries.

The first event in the blackout sequence was a generator shutdown, called a generator trip, that occurred at 12:05:44 pm at American Electric Power’s 375 megawatt (MW) Conesville Unit 5 in central Ohio.

The next event, at 1:14:04 pm, was a generator trip at Detroit Edison's 785 MW Greenwood Unit 1 north of the Detroit area. This generator returned to service at 1:57 pm.

The third event, which occurred at 1:31:34 pm, was a generator trip at FirstEnergy Corporation's Eastlake Unit 5 in northern Ohio along the southern shore of Lake Erie which is connected to the 345 kV transmission system.

"These generating unit trips (shutdowns) caused the electric power flow pattern to change over the transmission system," the task force said.

Next a transmission line that is part of a pathway from southwestern Ohio into northern Ohio disconnected from the system due to a brush fire under a portion of the line, the task force reports. "Hot gases from a fire can ionize the air above a transmission line, causing the air to conduct electricity and short-circuit the conductors," the report said.

And so on from one event to another through Ohio, into Michigan. As portions of the system shut down, the continuing demand for power increased the load on the parts of the system that were still functioning.

power plant

Power plants like this one on Lake Erie failed. (Photo courtesy NREL)
At 4:10:38 pm, the largest operating cogeneration plant in the United States, Midland Cogeneration Venture in Midland, Michigan loaded to 1265 MW, tripped off line. This imposed heavier flows on the remaining transmission system, and left eastern Michigan and northern Ohio with very depressed voltages. The remaining transmission paths into the Detroit area from the northwest separated, the task force said.

When the transmission lines along the southern shore of Lake Erie disconnected, the task force explained, the power that had been flowing along that path immediately reversed direction and began flowing in a giant loop counterclockwise from Pennsylvania to New York to Ontario and into Michigan.

The cascade of power outages then moved through Pennsylvania, New York, Ontario, Québec, and Maritimes areas, with heavy power flows tripping generators along this pathway, separating one system from the next in line until more than 50 million people were left in the dark.

"This outline does not attempt to present or explain the linkages between the sequences of events that are described," the task force said.

In the coming weeks, task force experts will continue to analyze data from the thousands of transmission line events that occurred on the 138 kV system and on lower voltage lines over the several hours before and during the grid's collapse.

They will analyze the hundreds of events related to power plant interactions with the grid during this period, and the conditions and operations on the grid before 12 noon that may yield clues to the cause of the blackout.

And they will examine any actions taken, or not taken, by system operators prior to or during the outage.

"While we are making good progress," Secretary Abraham said, "this investigation is far from complete. The task force and its working groups and investigation teams have much work ahead of them."