August 4, 2013

Inadequate transmission lines keeping some Maine wind power off the grid

Ratepayers will likely bear the cost of future upgrades to fix the problem, which could get worse.

By Tux Turkel tturkel@pressherald.com
Staff Writer

After spending $1 billion in Maine to build 11 projects, wind energy companies have a problem: The transmission lines connecting them to the New England grid sometimes are too weak to carry all their power.

click image to enlarge

First Wind’s Stetson wind farm, in Washington County near Danforth, is among the turbine projects in New England that sometimes can’t send their power into the grid because local transmission lines are too weak. The problem is expected to become worse as more wind farms are built, and the regional grid operator is exploring ways to improve the situation.

2010 Maine Sunday Telegram file photo/Gregory Rec

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When that happens, the region's grid operator orders the wind farms to reduce output or stop running, a process called curtailment. Letting them all operate at certain times could overload the grid and jeopardize reliable service.

The problem could get worse in the future, according to the grid operator, if many more wind projects go on line, as planned.

Wind companies knew about these constraints when they built the plants. But federal utility rules meant to encourage renewable energy let them install feeder lines that meet only minimum standards.

Upgrading transmission lines will take money, and that will come from ratepayers. It's too soon to say how much the upgrades would cost.

But the investors in wind farms still make money, even if the power isn't sold on the grid, because of how these projects are financed and the rates companies have negotiated for their energy.

Projects in Maine, where most of New England's wind output is located and where far-flung additions are planned, appear most at risk for being taken off line or cut back. That's because they are located in remote areas most likely to be serviced by dated transmission lines. Boston-based First Wind, Maine's leading developer, says roughly 20 percent of the power at four Maine projects was curtailed last year, although at least half of that was due to construction in a major transmission corridor.

Several strategies are under study by the power grid's independent systems operator, or ISO, to better integrate wind power into the system. Wind power produced 1 percent of New England's energy last year, up from virtually nothing in 2005.

Until now, the systems operator hasn't tracked how much wind power is being turned away, or which projects are most at risk of curtailment. It's starting to collect that information.

ISO-New England also is starting to develop more sophisticated ways to forecast what will be available from wind for next-day power production. That will become essential if New England develops an offshore wind industry, because wind patterns are different in the mountains than they are along the coast.

But these measures won't eliminate the need to beef up transmission lines closer to the turbines, according to Stephen Rourke, vice president for systems planning at ISO-New England.

"As we get more and more wind, we are going to need to see some enhancement to the network, more transmission lines built, to unlock large amounts of wind," Rourke said in an interview with the Maine Sunday Telegram. "Our work will help but not solve the problem."

In a recent background paper on the issue, ISO-New England set out the challenges.

The region now has 700 megawatts of installed wind capacity, with 500 megawatts in Maine. That's enough installed capacity to supply more than 150,000 homes, based on average annual output. Projects that could triple today's capacity are in the planning stages. The trouble is, most are located in rural areas, far from customers.

"The transmission resources in these parts of New England were built to serve the native load, but not designed to accommodate the addition of generation sources or the movement of large amounts of power," the paper explains.

A DOUBLE SET OF STANDARDS

More than 8,000 miles of high-voltage lines connect 350 power plants in the six New England states. Many lines are being upgraded, including Central Maine Power Co.'s backbone system that runs from Orrington through southern Maine. As part of CMP's upgrade, big 345-kilovolt lines were extended to Detroit and Lewiston.

(Continued on page 2)

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