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Blackout of 2003
Another line may have shorted out, utility says
08/27/03Peter Krouse and Teresa Dixon Murray
Plain Dealer Reporters
A second major Northeast Ohio transmission line linked to the largest power failure in U.S. history apparently shorted after sagging into a tree.
The South Canton-Star 345-kilovolt transmission line, one of several that connect FirstEnergy Corp. to American Electric Power Co., registered a ground fault as it went out of service Aug. 14, according to records released by American Electric Power.
AEP spokesman Pat Hemlepp said indications point to that ground trip being caused by contact with a tree somewhere on the portion of the line owned by FirstEnergy.
He would not reveal his source. American Electric Power owns less than one mile of the line where it connects to the South Canton substation in Stark County. The remaining 33-plus miles that dogleg north to the Star substation in Medina County are owned by FirstEnergy.
FirstEnergy did not deny the possibility that the line hit a tree, but spokeswoman Ellen Raines said, "At this point, we only have evidence of one tree contact and that's on the Hanna-Juniper line." That contact occurred in Walton Hills while workers hired by FirstEnergy were trimming trees nearby.
Steve Dupee, director of Oberlin Municipal Light and Power, said utilities should keep trees far away from big transmission lines.
The line from the Hanna substation in Portage County to the Juniper substation in Cuyahoga County carries thousands of times more voltage than ones seen on city streets.
"Anytime you see a transmission line, you'll see a wide-open swath cut around that," Dupee said. He added that utilities calculate possible sagging and plan generously for worst-case sagging. "Even though lines sag, they shouldn't ever touch the tree."
AEP is investigating whether two or perhaps three of its lines connecting AEP with FirstEnergy may also have had contact with a tree and shorted out. The East Lima-New Liberty 138-kilovolt line and the East Lima-North Findlay 138-kilovolt line both registered ground trips. But Hemlepp said sometimes a case of high load and low voltage, which existed at the time, can register a ground trip when there isn't one.
FirstEnergy normally cuts tree branches every five years in areas where they are near major transmission lines, Raines said.
In addition, workers inspect the transmission lines by helicopter or on foot at least twice a year - once in the spring and once in the fall, she said. Because some types of trees grow faster than others, workers trim some more often than every five years, Raines said.
In 2002, FirstEnergy did not trim branches in five areas where it had planned tree maintenance, according to a report filed with the Public Utilities Commission of Ohio, because "they were in good condition and maintenance could be deferred until 2003. Resources were used to maintain vegetation at other, more critical locations."
The areas were all near major transmission lines on FirstEnergy right-of-way property. Raines declined to say whether the Walton Hills area was among the locations where tree-trimming was delayed. But, she said, "We would only defer maintenance where it was unnecessary and when other areas needed it more."
The first transmission line to go out prior to the blackout was the 345-kilovolt FirstEnergy line connecting the Harding substation in Cuyahoga County to the Chamberlain substation in Summit County. It went down at 3:06 p.m. No reason has been given by FirstEnergy. An analyst with Cambridge Energy Research Associates, which has offered a hypothesis of how the outage occurred, has said it was not caused by an excessive amount of electricity on the line.
The 345-kilovolt Hanna-Jupiter line was next to go, at 3:32 p.m., followed by the South Canton-Star line at 3:41. Over the next 29 minutes, nine more lines connecting FirstEnergy transmission lines with AEP transmission lines were knocked out of service.
The severing of those ties apparently caused a surge in AEP power - still searching for the FirstEnergy customers it had been supplying - to shoot through Indiana and Michigan before returning to FirstEnergy's transmission area near Toledo, according to the Cambridge analysis.
That surge caused plants and transmission lines to shut down in Michigan and Ohio, putting them into blackout. It contributed, along with other events, to Ontario and New York blacking out as well.
PUCO spokeswoman Shana Gerber said state law doesn't require utilities to keep their lines certain distances away from trees. The state's investor-owned utilities, such as FirstEnergy and AEP, must simply establish a vegetation-control plan and file it with the state.
"They set their own clearance guidelines," Gerber said. "We just make sure they're meeting their own program goals."
The state's only mandate is that the utilities must do whatever they need to "in order to establish and maintain safe and reliable service," she said. Ohio and neighboring states have adopted national standards saying trees that can interfere with transmission and distribution wires should be trimmed or removed. The National Electric Safety Code also says that normal tree growth, adverse weather conditions, voltage and sagging at higher temperatures should be considered in determining the extent of trimming required.
While trees near lines pose a risk, Dupee noted that utilities often have trees around their rights-of-way because the public likes them. "A lot of people feel transmission lines are a blight on the environmental scheme," the director of Oberlin Municipal Light and Power said. "But if you have trees near those 345[-kilovolt] lines, I would think you'd want to pay big-time attention to them."
Plain Dealer reporter Becky Gaylord contributed to this story.
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© 2003 The Plain Dealer. Used with permission.
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