LANSING (AP) – The head of the state’s utility board on Friday dismissed speculation that Michigan may have been the starting point for Thursday’s widespread power outage.

All the DTE Energy plants that shut down went down simultaneously Thursday afternoon, making it unlikely that a problem at one plant triggered the closing of others or caused the collapse of the transmission grid, said Public Service Commission Chairman Peter Lark.

The state will know more about how millions of Michigan residents were left sweltering without lights or air conditioners after PSC staff delve into the outage. The commission on Monday plans to order an investigation into what caused Michigan to suffer the largest blackout in its history, Lark said.

Although no cause has been determined, officials are taking particular interest in a series of power line interruptions that occurred in the Cleveland area during the hour before the blackout hit Thursday, racing across the region from southern New England to Michigan.

Two minutes after the last of these Cleveland-area line problems there were “power swings noted in Canada and the eastern U.S.,” said a document made public late Friday by the North America Electric Reliability Council.

But the NERC document cautioned “it’s not clear if these events caused the (wider blackout) or were a consequence of other events.”

The outage stretched from the Northeast to Canada and Michigan, where it caused blackouts from Detroit to Lansing.

NERC spokesman Tim Gallagher said it’s unclear if the tripped lines were what started the power outage, or were just an effect of something else happening on the power grid.

About the time power was disrupted at 4:11 p.m. EDT Thursday, technicians noticed a stunning development on the northern leg of “the Lake Erie loop” that connects transmission lines in Ohio and Michigan before circling through Canada to New York: some 300 megawatts of electricity moving east into Ontario abruptly reversed course and within seconds 500 megawatts of power suddenly were moving west.

Electricity flows on its easiest path so it is believed the change in direction was caused by a sudden reduction in power somewhere on the line at the western end of the loop, investigators suggested.

“This was a big swing back and forth,” said Michehl Gent, president of NERC, an industry-sponsored group that tracks power grids to assure their reliability. Power levels began to fluctuate throughout the grid, causing generators and other systems to trip across the region to protect equipment.

Somewhere in the process, a number of power stations owned by Detroit-based DTE Energy and Jackson-based Consumers Energy Co. were knocked out, Gallagher said.

“There was an imbalance between supply and demand to the east of us and, almost instantaneously, that caused an imbalance of supply and demand in our system and the breakers opened,” said David Joos, Consumers Energy president and chief operating officer.

Lark said he was surprised so much of the grid collapsed in the United States and Canada and wants to find out how the state can protect itself from blackouts in the future.

The Public Service Commission already had a meeting scheduled for Monday, which is why the order to investigate the outage will be issued then, he said. “We’re going to look into it from a Michigan standpoint,” he added.

The Michigan and Ontario electrical grids, usually tied together at several points, remained unplugged from each other Friday, Gallagher said.

Deciding when to reconnect the two “is just going to depend on how long it takes them to get the system restored to the point where they’re comfortable and stable,” he said.

Michigan began deregulating its electricity market several years ago. As part of that, both DTE – formerly Detroit Edison – and Consumers Energy sold their transmission lines, Lark said.

Gov. Jennifer Granholm, in an appearance Friday night on CNN, said the transmission system is now run by owners outside the state and hasn’t seen any new investment for upgrades in 20 years.

“The people who own the transmission system are out of state and are not necessarily … accountable,” she said. “This issue of who owns the transmission, who owns the generation, who owns the distribution, all of those are areas we’re going to have to look at.”

Lark barely had time to get used to his new job as commission chairman before the outage hit. The appointment of the former state assistant attorney general took effect Aug. 4 and was approved Wednesday by the state Senate, just a day before a portion of the state went dark.

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