More than 600 angry Washington and Greene county residents turned out last night at the Washington County fairgrounds to oppose the construction of a high-voltage power line in their area.

The event, organized by the citizen's group "Stop The Towers," also drew a flock of local and state politicians, most of whom vowed to fight the project by Allegheny Energy Inc.

The plan involves the Greensburg-based energy company's proposed construction of a 240-mile, 500-kilovolt transmission line, extending from Washington and Greene counties to existing substations in West Virginia, ending in northern Virginia.

Also part of the plan is the construction of two substations, including a 502 Junction substation in Dunkard, southern Greene County, which will direct flow northward in Washington County and eastward into West Virginia.

The other substation, nicknamed Prexy, will be built along Thomas Eighty-Four Road in North Strabane, Washington County. It will include three smaller transmission lines that will branch off into South Strabane, Nottingham and Somerset townships.

Allegheny Energy's portion of the line extends about 210 miles at a cost of $820 million, with the total project estimated at more than $1 billion. The smaller portion of the line will be constructed and paid for by Dominion Virginia Power, which serves customers in Virginia.

Company officials have said they believed there was a misunderstanding over who would benefit from the new lines. Misconceptions that southwestern Pennsylvania would be providing power for Virginia are incorrect, officials said.

But many of the residents who turned out at last night's meeting, and another held Tuesday night by the company, said they don't buy it.

"I don't believe that," said Washington County Commissioner Larry Maggi after a company open house Tuesday at the Bentleyville Fire Hall. "They are having problems on the East Coast."

Tuesday's event was one of 10 open houses sponsored by Allegheny Energy during recent weeks to explain the company's plans. Although the Mid-Atlantic, from New York to northern Virginia, was identified by the federal government last year as an area in critical need of more power, company officials said power lines in southwestern Pennsylvania will serve electric needs in this area only. A separate line, at the 502 junction in Greene County, will transmit electricity to northern Virginia.

Residents said they believed the project would decrease property values and the quality of life, and possibly be a health and safety hazard. They also questioned the company's claim that it owns rights of way along all but two miles of the proposed 38-mile route through Washington and Greene counties.

"We are opposed to it," said Mr. Maggi. "We will do whatever we can to stop it. We do not want to lose our country charm."

"What do we get out of it? Nothing. We lose," said county Commissioner Diana Irey.

U.S. Rep. John Murtha, D-Johnstown, in a letter made public last night, opposed the power line project for the first time. He is congressman for a large part of the affected area.

Wendell Holland, chairman of the state Public Utility Commission, explained PUC procedures to last night's audience and said:

"There's nothing like being here. There's nothing at all like coming to the people and listening to what they have to say."

The upgrade was mandated by PJM Interconnection, which manages electric transmission services of the Mid-Atlantic power grid in 13 states and Washington, D.C. The proposed line is part of PJM's five-year regional electric transmission plan, meant to address future energy needs at certain points in the grid, such as southwestern Pennsylvania and northern Virginia.

If local lines aren't updated to a higher capacity, company officials have said customers in southwestern Pennsylvania can expect rolling blackouts and brownouts by 2011.

The existing 138-kilovolt lines aren't large enough to accommodate electricity load growth rates of about 4 percent in central and northern Washington County. Growth rates elsewhere in the region average about 1¹/₂ percent, company spokesman David Neurohr said.

PJM has asked Allegheny Energy to make the southwestern Pennsylvania line a priority, said company officials, requesting that the project be completed by 2010 if possible. It will be built even if a line to northern Virginia is not, Mr. Neurohr said.

The company is expected to file an application with the PUC soon, as it did in West Virginia last week. If construction permits are denied or not issued within the next year, it could kick in a backstop provided for in the Energy Policy Act of 2005, which gives the federal government the right to intervene with construction permits.