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Power Play

Impressive, maybe, but these systems are still more or less Band-Aids. The installation at Marcy represents the first attempt at major surgery for the grid. The diseased arteries are the two 345,000-volt transmission lines that run south from Marcy to New York City: one skirts Albany and then chases the Hudson; the other traverses the Catskill Mountains to the west before it heads for Manhattan. With a push of a button, a series of breakers at Marcy will reconfigure the station’s circuits to pump electricity from one line to the other as needed ( see “The Electronics Solution at Marcy,” below ).”We will have the ability to actually alter the flow of energy-take it off of one line, put it on another line, particularly if that line is starting to get into an overload condition,” says Gerald LaRose, who runs the Power Authority’s mission control center at Marcy.

LaRose is particularly eager to relieve the line connecting Marcy to New York City via Albany. The operators know it as Marcy-South, and it is easily the state’s most congested high-power transmission line, stuffed to capacity 25 percent of the time and skating within 100 megawatts of overload for much of the rest. The line is obsessively monitored, and each time it approaches critical, the New York Independent System Operator, the agency that manages the state’s grid, must cease adding power to it-indeed, to all of the highly connected circuits running throughout central New York. Even those lines with spare capacity must be squelched, since some fraction of any additional power could reach the stressed Marcy-South line and push it over the edge.

On a hot day when power demand is peaking, squelching electricity flowing from upstate could spell trouble in New York City. At best, the city must fire up expensive and polluting gas- or oil-fired power plants to make up for the constrained flow of hydropower from Quebec. At worst, neighborhoods could be plunged into darkness. While this worst-case scenario has yet to happen, experts agree that New York City is becoming ever more vulnerable.

Then there is the matter of getting cheap electricity to Long Island, one of the country’s fastest growing areas. There, too, power electronics could change everything. The problem is that New York City literally stands between Long Island and cheap power. Squeezing more electricity past this massive bottleneck is nearly impossible. The transmission lines running into New York City are simply too full to carry additional power onward to Long Island. So while Connecticut residents just 40 kilometers away across the Long Island Sound gorge on vast amounts of cheap juice flowing down from Canada’s hydroelectric plants, the eccentricities of the existing grid mean electrically isolated Long Islanders must fend for themselves, relying on local generators to supply a hefty 93 percent of peak power demand. This is one reason that Long Island endures some of the highest electricity rates in the country.

Power electronics is providing a solution so compelling that it is driving the construction of the first U.S. high-power line built by transmission entrepreneurs, who see a huge profit in bridging Long Island’s power gap. As in the Marcy system, two power processors will control energy flow on this transmission line, which will stretch underneath the sound. But instead of sitting back-to-back as they do at Marcy, the processors will lie on opposite shores, sucking AC power out of one grid, pumping it as DC power under the sound via a 42-kilometer underwater cable, and regenerating the AC wave on the other side. (The conversion to DC cuts costs, because underwater AC cables are more expensive than their DC counterparts.) “You want 100 megawatts to go in one direction? Just turn the dial. Want it in the other direction? You just turn the dial,” says Jeffrey Donahue, president of Transnergie U.S., a subsidiary of Montreal-based power giant Hydro-Qubec and the builder of the $120 million link.

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