The Nuclear Regulatory Commission's headquarters in Rockville, Md., said each of the nuclear plants was operating in a safe mode on backup power. Utilities said it could be days before they're at full power and generating electricity.
The massive effort of restoring power includes coordination of several states to guard against fluctuations that could lead to more damage, officials said.
Locally, each system was inspected for damage before it was restarted - a process that further slowed the restart effort. “We won't bring back customers only to have their power go out five minutes later,” Chuck Krueger, a Toledo Edison Co. spokesman, said.
Detroit Edison Co.'s Fermi II nuclear plant in northern Monroe County and FirstEnergy Corp.'s Perry nuclear plant east of Cleveland were among the nine that were shut instantly.
The process of restarting nuclear plants is more involved because of the complexity of the technology. “You can't just turn them on by flipping a switch,” John Austerberry, Detroit Edison Co. spokesman, explained.
Nuclear power produces 20 percent of the nation's electricity. By having nine plants shut down at once - plus having Davis-Besse idle - the nation lost production from nearly a tenth of its 103 nuclear plants.
Electricity slowly was being restored at FirstEnergy's Bay Shore coal plant near Toledo starting about 6:30 p.m. The process was to take hours, Mr. Krueger said.
Tony Earley, chief operating officer of DTE Energy, Detroit Edison's parent company, said Detroit was unlikely to have power restored today. As of last night, the only Detroit Edison customers to have power restored were in Michigan's Thumb region and other rural areas, he said.
“The risk is if we bring back the system too fast, it won't be able to handle the load,” Mr. Earley said, adding the process likely would take the rest of the weekend.
Detroit businesses were urged to stay closed today. “If we have a normal weekday tomorrow, we will not have enough to handle the load. That's why we're requesting that businesses treat it like a long weekend and stay closed,” he said. “This isn't a Detroit Edison issue. This is a national issue. The grid is designed to be inter-connected.”
An electric grid has circuit breakers much like a house, intended to shut off damage from a bigger cascading failure, said Charlie Severance, director of strategic business development for WPS Energy Inc., of Green Bay, Wis.
WPS supplies power to parts of the Toledo area under the state's electric-choice program, but its electricity is transmitted through power lines of Toledo Edison, which is owned by FirstEnergy Corp. of Akron.
Some circuit breakers reacted fast enough to preserve power in small pockets around northwest Ohio even while major metro areas, such as Toledo, generally were dark.
Areas that kept power included parts of West and South Toledo, Perrysburg, and other isolated locales, plus parts of Findlay and Bowling Green.
``The automatic trips kicked in, so the system worked as it was meant to,'' said Kristen Baird, a spokesman for FirstEnergy. ``There are outages, but Toledo is in decent shape,'' Ms. Baird said last night.
But the remainder of FirstEnergy's 2.2 million customers in Ohio didn't fair as well.
The cascading power failure initially knocked out six FirstEnergy generating plants in Ohio that provide the utility with about 5,000 of its 13,000 megawatt generating capacity.
FirstEnergy's Ohio plants in Mansfield and Stratton were unaffected, as was its Beaver Valley nuclear plant in Western Pennsylvania and its gas-fired standby plant near Defiance, Ohio.
Mr. Severance said the key to keeping power flowing during the bigger grid failure was being in an area where power demands did not exceed supply to that area and require supplemental power from elsewhere.
``Let's say the city of Pittsburgh and the surrounding county had enough generation being supplied to it to serve that load and that four or five additional lines came into that area to offset increased demand.
“When the failure comes, if those circuit breakers on those lines coming in are tripped quick enough, you cut off that area from the outside,'' Mr. Severance said. ``And if the load in that area was balanced with supply, the area would able to balance itself and maintain power.
``But if the lines coming in aren't tripped quick enough, there would be a surge that would black out the entire city,'' he added.
Islands of power formed in the Toledo area because there were pockets where the circuits reacted quickly enough to cut those areas off from the cascading grid. Power still was being sent from FirstEnergy power stations to those pockets.
Mr. Severance said northwest Ohio was fortunate in that it was at the far western end of the power failure, which rolled east to west.
``It sounds like there are several incredibly large transmission lines that come from Canada and that the power loads were pretty heavy there. When one line [shut down], the other lines had to pick up that load. If one of those overloads, it will trip over and that means there's that much load on the other lines,'' Mr. Severance said. ``I suspect what happened there was a cascading effect and in most places the grid collapsed before these islands of power could form.''
Restarting the system is done in a backward manner, he said. Pockets are isolated intentionally and power to meet the demand of that pocket is supplied. Pockets are restarted one by one.
``They have generators with what they call `black start' capability. They get it ready and then they flip a switch to handle some specific load. They get that area in balance and then move on. The recovery time will take hours as long as there is no major damage,'' he said.