Heat wave stresses Mid-Atlantic power grid again

NEW YORK (Reuters) - U.S. electric companies urged consumers to keep cutting back on energy use on Wednesday as a record-breaking heat wave kept a stifling grip on the Mid-Atlantic states, straining power plants and distribution lines and leaving some customers without power.

Consolidated Edison Inc of New York said it had restored power to about 18,700 customers in the metropolitan area over the past 24 hours, but still had 6,300 homes and businesses suffering in the triple-digit heat without service.

Forecasters predicted no relief from the scorching heat on Wednesday. The mercury in New York, Philadelphia and Washington could reach 100 degrees F (about 38 degrees C) for a second consecutive day before dropping to the low 90s on Thursday.

Despite the heat, which on Tuesday set records for the date in New York, Philadelphia and Boston, and many other areas, the region's grid operators forecast peak electricity demand on Wednesday would not break record highs set during a brutal heat wave in 2006.

Utilities said the region had enough power to keep air conditioners humming even with the mercury returning to the triple digits from New York to the Carolinas.

Still, authorities were taking precautions to prevent any disruptions to service.

The state-owned New York Power Authority on Wednesday again activated its demand response program, which pays large business and government customers, such as Citibank and New York City, to cut back on energy usage.

Con Edison asked businesses and government offices in New York to conserve energy by shutting nonessential lights and discretionary equipment, such as extra elevators or escalators, turning off pumps for ornamental fountains, limiting the cooling of buildings, and using emergency generators to offset some of the electricity they take from the power grid.

On Tuesday night, Con Ed imposed a voltage reduction, or brown out, of up to 8 percent in parts of Brooklyn and Queens to allow workers to fix overheated cables supplying power to several neighborhoods.

PEAK DEMAND RECORDS TO SURVIVE

While the utilities struggle to keep up with the demand, the regional grid operators, which oversee several local power companies, do not expect to see their 2006 records fall.

PJM, operator of the biggest grid in the United States, forecast peak demand Wednesday would fall short of the all-time record because the heat was baking only the eastern part of its territory.

"To break the 2006 peak, it really needs to be hot everywhere, not just in the East," PJM spokesman Ray Dotter said Tuesday.

PJM's power usage reached 136,398 megawatts on Tuesday, the highest since 2007, and was expected to climb even higher to about 137,800 MW Wednesday afternoon.

That was still well short of the grid's all-time record of 144,644 MW set in August 2006 when a brutal heat wave blanketed the entire system.

PJM serves more than 51 million people in all or parts of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia.

One megawatt powers about 1,000 homes.

The New York Independent System Operator, which operates the state grid, said demand Tuesday reached 33,452 MW, easily beating the 2009 peak, but just short of the all-time record of 33,939 MW set in August 2006. For Wednesday, the ISO forecast demand of just over 31,000 MW.

ISO New England, which operates the region's six-state power grid, forecast demand Wednesday would reach 27,000 MW for a second day in a row, beating last year's peak, but still about 1,000 MW shy of the August 2006 record of 28,130 MW.

(Reporting by Scott DiSavino; Editing by Walter Bagley)