HOUSTON, June 9 Power grids and utility delivery systems in the eastern United States mainly held on Monday and were expected to handle the strain as well on Tuesday as the first heat wave of the summer extends to a fourth day, utility and grid officials said.
On Monday, record temperatures over much of the state caused the New York power grid to surpass last summer's peak demand.
And it isn't even summer yet, pointed out Ken Klapp, spokesman for the New York Independent System Operator. Summer officially begins June 21 and record peak power demand is generally reserved for July and August.
The heat is expected to loosen its grip on the East by Wednesday, when New York City is to have a high of 87 degrees Fahrenheit (30.5 Celsius), down from 97 F (36.1 C) on Tuesday and 99 F (37.2) on Monday.
Scattered outages were experienced Monday in the Mid-Atlantic states, where the biggest single blackout -- in New Jersey -- affected 75,000 customers. Most of the houses and businesses without lights were expected to have power restored by Monday evening, said utility PSE&G, which is a unit of Public Service Enterprise Group (PEG.N).
A fire at a switching station in West Orange caused the blackout, and PSE&G officials said they did not know if the issue was related to the heat wave.
"The New York ISO (Independent System Operator) had no problems today," said Klapp, who said the state's power grid had an average peak between 4 and 5 p.m. Monday of 32,432 megawatts. That was 263 MW more than last summer's high, which was not experienced until early August. Tuesday's demand is forecast at just less than 32,000 MW.
"We had adequate reserve margins," he said. Every utility watches that cushion between demand and power supply closely and takes steps to pare demand if the reserve margin gets too thin.
Klapp and Ray Dotter of the PJM Interconnection power grid -- which covers 13 states from North Carolina to Michigan -- said utilities did not have to pare demand on Monday and are not expected to call for it on Tuesday.
Dotter said that while there have been no demand-response programs called upon yet, utilities have been asked to postpone routine maintenance on their generation plants and transmission lines.
A megawatt in the eastern United States can serve about 800 homes under normal conditions, but less than that during a heat wave when air conditioners increase per-customer demand.
The NYISO's record peak was 33,939 MW on Aug. 2, 2006.
At PJM, the largest U.S. power grid operator, Monday's pull on the system was about 130,000 MW, and Tuesday's is expected to fall off a bit to about 125,000 MW. This is well below the PJM record of 144,644 MW set in August 2006.
However, Dotter said, the eastern part of the grid including New Jersey, Pennsylvania and the rest of the mid-Atlantic will likely see almost as much power use as on Monday.
In New England, the grid operator, ISO New England, forecast demand would reach about 25,980 MW Monday and 27,020 MW Tuesday before sliding Wednesday. That is still well below the region's all-time record of 28,130 MW set in August 2006.
"We expect normal operating conditions barring any unexpected generation or transmission shutdowns," spokeswoman Erin O'Brien at ISO New England said.
The cooling trend that will reach the East on Wednesday is expected on Tuesday to cool Chicago and other major high power users in the Midwest, Dotter said. (Additional reporting by Scott DiSavino; Editing by Gary Hill)