COLUMBUS, Ohio -- Two Ohio companies at the center of the investigation into the nation's worst blackout warned state regulators five months ago that their power systems could overload if the grid linking U.S. and Canadian utilities had problems.
FirstEnergy Corp. and American Electric Power said in long-term forecasts that they didn't expect any of their own transmission lines or substations to fail this summer.
But both companies said that widespread outages were possible if the spaghetti-like system that links eastern states and Canada experienced unexpected changes in electricity flows, power transfers between regions, unexpected demands and extreme weather.
"Together, these factors ... may lead to overload conditions," FirstEnergy said.
Those are just the sorts of power grid disturbances that swept across eight states and the province of Ontario, Canada, on Aug. 14, spreading the outage to 50 million people.
Akron-based FirstEnergy is at the center of a U.S.-Canada inquiry of what caused the outage. The most prominent theory is that a FirstEnergy power plant in Eastlake, Ohio, and some of its electricity transmission lines failed, including one that sagged into a tree.
The resulting surge of power in Ohio spread, rocketing across transmission lines in Indiana, Michigan, Ontario, and New York and setting off automatic power shutdowns.
The two Ohio power companies say the Public Utilities Commission of Ohio has heard the same grid overload warnings from them for years and there is nothing that state regulators could have done with that information to prevent the blackout.
"It's just a statement of reality. It's a recognition of the fact that we are all interconnected and that there are strengths and weaknesses to that," Ralph DiNicola, a FirstEnergy spokesman, said Monday.
"The good is that being interconnected enhances reliability. The not-so-good is that what happens on adjacent systems could impact our system," DiNicola added.
Shana Gerber, a PUCO spokeswoman, said state regulators don't have the authority to help the utilities solve such reliability problems.
"All we can do is encourage these companies to participate in a regional transmission organization in which they can solve these issues internally," she said.
In Indiana, James P. Torgerson, chief executive of the Midwest Independent Transmission System Operator, told state regulators Monday that the grid manager has increased monitoring of FirstEnergy, adding data collection points to watch voltage flows on its lines.
Torgerson also said the Midwest operator needs to improve communication among utilities, which now rely on old-fashioned telephone warnings to relay problems. On the day of the blackout, there was little or no warning for most U.S. utilities and Canada.
"It's not very efficient when you have to start calling everybody," Torgerson told the Indiana Utility Regulatory Commission.
Control room operators called FirstEnergy when they detected problems, but didn't spot other conditions that would lead to a widespread outage, the Midwest group said.
FirstEnergy and AEP say investigators must look at what was occurring on the entire grid inside and outside Ohio in the hours before the blackout because abnormal activity elsewhere could have impacted their power systems' operations.
The PUCO asked power companies in an Oct. 15, 2002, letter to say in their annual long-term forecasts which transmission lines or substations were most likely to be overloaded and under what conditions. FirstEnergy and AEP filed their reports in April.
FirstEnergy identified none of its transmission system as failure prone. Parts of its report were sealed with some documents marked confidential. The utilities commission has asked it and other utilities to explain why the documents should not be released.
AEP's report said a transformer at its South Canton facility in northeast Ohio was the most likely to overload if other utilities on the grid had outages or heavy demand.
The Columbus-based company said it would install a higher-capacity transformer before this summer to prevent problems. AEP spokesman Pat Hemlepp said that work was done, increasing the transformer's capacity by 5 percent.
About 30 minutes before the blackout, a line co-owned by FirstEnergy and AEP tripped as too much electricity coursed over it. The line is connected to the South Canton facility, where FirstEnergy's grid interconnects with AEP's neighboring grid.