AUGUSTA, Maine – Two utility companies unveiled plans Tuesday for a $1.9 billion overhaul of Maine’s electricity transmission lines aimed at bolstering reliability and encouraging large-scale wind power development in Aroostook County.

Central Maine Power and Maine Public Service Co. filed applications on Tuesday with state regulators for two massive transmission line projects. If approved as proposed, the projects would likely be paid for by all New England energy consumers with Maine ratepayers accounting for about 8 percent of the cost, officials said.

The first project would build an additional, 345-kilovolt transmission line along the existing CMP corridor, passing through nearly 80 communities from Orrington to Newington, N.H. The $1.4 billion expansion is part of a long-term plan to upgrade the state’s aging power infrastructure, which studies predict could encounter serious reliability problems as early as 2012 without major fixes.

The second project would connect northern Maine communities to the New England power grid. While such a connection has been discussed for years, it was regarded as economically unfeasible until recently when Aroostook County became the hot spot for potential wind farm development in the state.

Brent Boyles, president and CEO of Maine Public Service, said the northern Maine transmission line upgrade is tied to Horizon Wind Energy’s proposed development of up to 800 megawatts of wind energy in The County.

That proposal, which would comprise several separate projects, would transform the landscape of Aroostook County with 400 wind turbines — each standing roughly 400 feet tall — dotting farm fields and hillsides.

A subsidiary of Horizon Wind, Aroostook Wind Energy, has been busy lining up willing landowners, but opposition to the unprecedented project is brewing.

Boyles said the two transmission line projects, combined with Horizon Wind’s proposal, would generate thousands of construction jobs and funnel tens of millions of dollars into municipal coffers.

“If Maine has ever seen this level of economic activity before, it surely hasn’t been recently,” Boyles said during a press conference in the State Capitol. “Wind projects will transform Aroostook County’s economy, and these transmission projects will significantly benefit the economy of the entire state.”

Tuesday’s announcement highlights some of the financial and logistical challenges facing utilities, all of which directly affect ratepayers.

Maine’s electricity transmission infrastructure has not changed much since 1971, but demand has increased significantly over that time. Meanwhile, demand for electricity from renewable sources is growing thanks to a combination of skyrocketing energy prices, changing social values and government policies aimed at encouraging “green” energy.

Yet Maine — and particularly northern areas — lacks the transmission capacity to accommodate larger renewable energy projects.

That transmission line bottleneck became painfully evident last month when the architects of a proposed biomass energy plant near Millinocket found out access to the power grid was maxed out. Another renewable energy company, First Wind, had secured the remaining access for its Stetson Mountain project, a 38-turbine wind farm now under construction near Danforth.

Sara Burns, president and CEO of Central Maine Power, said Maine is at an energy “crossroads.” Oil and natural gas produce 74 percent of the state’s electricity, which Burns said is the reason why “small general service rates” have risen roughly 50 percent since 2000.

“We have an opportunity to begin to change this fuel mix in Maine,” Burns said.

Erin O’Brien, spokeswoman for New England-ISO, the region’s power grid operator, said Maine’s existing system is “nearing its limits” in terms of capacity and reliability.

New England-ISO has been working for several years with CMP and Bangor Hydro-Electric Co. on plans to upgrade transmissions lines. O’Brien would only say that the organization is continuing to study the prospect of connecting northern Maine to the grid.

But O’Brien said diversifying the source of power by adding more renewables to the region’s energy mix should enhance reliability and reduce the rate fluctuations tied to fossil fuel prices.

“A blend of resources will best serve New England’s needs moving forward,” she said. “There is no single solution.”

Maine state government is actively encouraging development of wind energy by designating large portions of the state — including much of The County — as areas for expedited regulatory review of wind projects.

Boyles said Maine Public Service has received inter-connection requests for 1,250 megawatts of wind power, including Horizon Wind’s 800 megawatts worth of projects. He declined to name the other developers or locations, citing federal disclosure rules.

Boyles and Burns said they hope northern Maine will be connected to the New England power grid by late 2010, thereby allowing the first phases of Horizon Wind’s projects to come on line. Boyles said his company already holds the right-of-way for a 25-mile gap between the two transmission lines.

“For years, we kept it clear” with plans to build, Boyles said. “Up until now, we didn’t have an economic reason to build. Now with wind [projects] we do.”

Gabriel Alonso, chief development officer for Texas-based Horizon Wind, said the company is making progress lining up landowners willing to host turbines in return for sizable annual lease payments. The individual projects will be built in stages if they receive regulatory approval. But Alonso said he hopes the first phase will be operational by late 2010.

“We will see,” Alonso said. “The process will take some time.”

The two transmission line proposals would face funding problems without ISO-New England’s assistance, and funding from ISO-New England is not a sure thing even if Maine chooses to stay in the regional power grid, said Richard Davies, Maine’s public advocate. In recent months Maine has been exploring the possibility of withdrawing from the grid.

The many factors at play complicate the playing field, but it’s clear that something needs to be done to prepare for wind power projects, boost competition and maintain the reliability of the power grid, Davies said from his office in Augusta.

“It’s somewhat akin to playing three-dimensional chess while blindfolded,” Davies said. “We don’t have much choice but to go forward based on the information we have now and figure out a way to evolve if something new comes along.”