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Power Grid Fends Off Soaring Temperatures, Record-Breaking Demand

Broiling heat and record-breaking demand across several parts of the country last week sorely taxed the U.S. power grid, but utilities and grid operators were able to successfully meet demand while avoiding a repeat of the disastrous August 2003 blackout.

One of the more dramatic events of last week was PJM Interconnection's decision on Wednesday to institute a 5% voltage reduction in portions of its territory to maintain system reliability in the face of an intense heat wave.

The voltage reduction initially was instituted for the utility territories of Baltimore Gas & Electric, Potomac Electric Power (Pepco), Dominion and the Potomac Edison portion of Allegheny Power. The voltage reduction later was extended to the territories of Public Service Electric & Gas (PSE&G), PECO Energy, Jersey Central Power & Light and the eastern portion of PPL Electric Utilities.

PJM on Wednesday night canceled the voltage reduction, along with a request for public conservation of electricity in the Mid-Atlantic region and Virginia. PJM said it had adequate electricity supplies to meet the demand for power throughout the day. With the arrival of cooler temperatures, electric system conditions were expected to get back to normal last Thursday.

Meanwhile, power grid operators and utilities alike across the U.S. knocked down old electricity demand records. ISO New England (ISO-NE) on Wednesday reported that New England's electricity use reached an all-time high. Preliminary data collected by the ISO showed that electricity use reached 26,942 MW, surpassing the previously established record of 26,749 MW set a week ago, on July 19.

Philadelphia's PECO Energy Wednesday said that power demand had reached a new all-time high. PECO Energy reported power demand on its system peaked at 8,695 MW at 5 p.m. Wednesday afternoon, only a day after a three-year old record was broken Tuesday.

PECO saw peak demand rise a bit each day -- only 6,044 MW on Sunday with a high temperature of 89 degrees, 7,740 MW on the first business day of the week with temperatures reaching 96 degrees, 8,359 MW on Tuesday when the mercury rose to 97 degrees, and 8,695 MW Wednesday in the late afternoon when power from the residential, commercial and industrial customers combined to plateau for the day.

The peak demand represents the highest amount of electricity being used during the peak hour of the day, while total electricity delivered on Tuesday exceeded 165.7 million kilowatt-hours, which also set a new record for a 24-hour period. The previous record for a day was established July 6, 1999.

In New York, Con Edison Wednesday night said it set a record for peak electricity demand of 13,059 MW at 5 p.m., eclipsing the former record of 13,003 MW set earlier Wednesday at 4 p.m. Wednesday also marked the first time in Con Edison's 123-year history of delivering electricity that peak demand had surpassed the 13,000 MW mark. Four of the top 10 electric peak loads of all time have been reached so far this summer.

Earlier in the week, the New York Independent System Operator (NYISO) on Tuesday said that for the second consecutive week, extreme heat and humidity drove statewide electricity usage to record level. Between 4 and 5 p.m. Tuesday, the NYISO recorded an hourly average peak load of 32,075 MW, which broke last week's record of 31,741 MW, set between 3 and 4 p.m. July 19.

Turning to the South, South Carolina Electric & Gas Co. (SCE&G) for the second straight day set new records Wednesday for peak demand on its system and overall usage of electricity by its customers.

The company's system-wide peak demand reached 4,820 MW for the one-hour period ending 4 p.m., topping the short-lived high mark of 4,692 MW, set on the previous day. Prior to the current heat wave gripping South Carolina, SCE&G's peak demand record had stood at 4,574 MW for more than a year; that mark was set July 14, 2004.

Again breaking the previous day's record, SCE&G customers used a one-day record of 95,639 MWh of electricity, topping the previous day's high of 91,013 MWh. SCE&G had sufficient internal generation to meet the high load demand for both days.

For the second day in a row, Progress Energy Carolinas customers set a record for peak electricity usage Wednesday. In fact, customer electricity usage July 27 set an all-time 24-hour record.

Between 4 and 5 p.m. Wednesday, Progress Energy's 1.4 million customers in the Carolinas used an estimated 12,572 MWh of electricity, eclipsing the record set Tuesday afternoon (12,232 MWh). For the full day, customers used a total of 250,671 MWh, which surpassed the 24-hour record set Jan. 19 of this year (245,977 MWh).

Before Tuesday, the previous summer peak-demand record was 11,977 MWh, set in July 2002. The previous all-time record was 12,004 MWh, set Jan. 24, 2005.

The Tennessee Valley Authority (TVA) on Tuesday reported that it met the highest demand for electricity ever recorded in its seven-state service area Monday, July 25, exceeding the previous record by more than 1,500 MW without a single sustained interruption to its customers.

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