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Texas grid ends power alert; extends conservation call

Jan 6 (Reuters) - Texas power grid conditions had returned to normal by mid-morning Monday, the grid operator said, hours after declaring an emergency to deal with soaring power demand as residents turned on heaters to cope with frigid weather.

The Electric Reliability Council of Texas (ERCOT), which had declared the emergency at 6:47 a.m., asked residents to keep taking steps to conserve electricity. The grid agency was able avoided rotating outages by calling on demand response programs under which some customers curtail power use in times of high demand.

"Cold weather will continue through tomorrow morning, and we will continue to monitor conditions closely," said Dan Woodfin, ERCOT director of system operations. "Consumers are encouraged to use electricity wisely, and a conservation alert remains in effect throughout the ERCOT region."

Operators at the Luminant's Comanche Peak nuclear plant, one of the largest power plants in the state, reduced power at one of two reactors early Monday, according to nuclear regulators. .

Real-time power prices jumped to $5,000 per megawatt-hour at 6:30 a.m. (0030 GMT) and remained at or near the $5,000 price cap for the next hour before dropping below $1,000, according to the ERCOT website.

ERCOT implemented two stages of its emergency plan to protect the grid as power reserves dropped below 1,750 megawatts.

One megawatt can power about 500 homes during mild weather conditions and about 200 homes during high-demand months, ERCOT said.

Power demand reached 54,486 MW in the hour ending at 8 a.m. Monday, the grid agency said, shy of the all-time record for January.

Tuesday morning's power demand is forecast to reach 56,018 MW, according to the grid website.

ERCOT said it issues power warnings when there is a likelihood rotating outages will be needed to reduce load.

Rotating outages are controlled, interruptions of electrical service usually lasting up to 45 minutes that are initiated by each utility when supplies of reserve power are exhausted. Without this safety valve, ERCOT said generators would overload and begin shutting down to avoid damage, risking a domino effect of a region-wide outage.

The biggest power companies in Ercot include units of privately held Energy Future Holdings, CenterPoint Energy Inc , American Electric Power Co Inc, PNM Resources Inc, NRG Energy Inc, Calpine Corp and Exelon Corp.