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For the second time this month, frigid temperatures are putting the heat on the Tennessee Valley Authority.

With temperatures projected to drop into single digits today and Friday in parts of TVA's seven-state region, the federal utility is operating under a power supply alert and may again briefly limit electricity to customers with interruptible service contracts to ensure adequate power delivery for most of the 9 million people served by TVA.

A majority of homes and offices in the Tennessee Valley are heated with electricity and cold temperatures this morning could push TVA's overall power demand above 32,000 megawatts for the second time in three weeks. On Jan. 7, TVA set an all-time record for the most electricity used in a single day when temperatures never got above 21 degrees Fahrenheit in the Valley. Temperatures remained below freezing for nearly three days in Chattanooga.

"We did exercise our right to reduce some power delivery for those with interruptible power contractors for a few hours (on Jan. 7), the first time we had done that in several years," TVA spokesman Jim Hopson said. "We have alerted our customers with interruptible service contracts that we may have to curtail some power again."

TVA is operating under a conservation operation alert to limit any unnecessary maintenance work that could jeopardize power generation and the utility is preparing to fire up its combustion turbines and other generators to help meet the high power demand through Friday.

TVA is benefiting by abundant water in its upstream reservoirs to maximize its hydro generation from its 29 power-generating dams. But TVA is without either the Raccoon Mountain Pumped Storage Plant, which is still being repaired, or its new Watts Bar Nuclear Plant Unit 2, which won't be finished until the end of next year.

More than 1,200 customers with interruptible power contracts were affected by TVA's power curtailment on Jan. 7 and collectively they reduced consumption at the peak by more than 1,000 megawatts. Most businesses reduced operations or delayed some work during the interruption and made up for the lost work time later.

The power interruption forced the closing of Murray State University in Kentucky, and 40 percent of the MSU buildings suffered damages from frozen pipes when a backup generator failed to work as planned. Classes were not in session at Muray State at that time, however.

At Severstal Columbus, a steel mill in northern Mississippi, electricity use was cut late Jan. 6 from 325 megawatts to 85 megawatts and didn't return to normal until 9 a.m. the next morning.

"Without the process heat we did experience some moderate water freezing issues," said Barry Steele, the power distribution and energy systems supervisor at Severstal. "However, none of them created serious production issues upon restarting our operation."

TVA customers with interruptible power contracts agree to limit their power use within five minutes of a notice from TVA. In exchange for agreeing to such temporary interruptions, such customers enjoy more favorable electricity prices. TVA has not had to interrupt power for such customers in several years due to milder winters and the recession-induced cutback in overall demand.

Overall, TVA has maintained reliable delivery of electricity to its customers equal or greater than 99.999 percent every year since 2000.

TVA's all­-time record winter demand peak was set on the morning of Jan. 16, 2009, at 32,572 megawatts when temperatures across the Tennessee Valley averaged 9 degrees. The all­time record demand on the TVA power system was 33,482 megawatts on the afternoon of Aug. 16, 2007, when temperatures averaged 102 degrees.

Contact Dave Flessner at or at 757-6340.