A hot day, big demand, and pop goes the power

By Erin Ailworth
Globe Staff / July 8, 2010

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No matter how well-prepared electric utilities may be, on a hot day the demand is sometimes too much for one circuit or cable, and pop: Somewhere, the power goes out.

If the problem occurs within NStar’s transmission network, two things happen nearly simultaneously: An alert goes out to the utility company’s engineers and dispatchers; and a light blinks on the “Big Board,’’ a computerized map of transmission lines that occupies one long, crescent-shaped wall in NStar’s energy management center on Massachusetts Avenue.

Lights flashed Tuesday night, when 4,000 NStar customers found themselves without electricity because of outages scattered across the company’s service region, which stretches from Burlington to Marshfield. More than 2,500 National Grid customers also went dark.

Utility crews worked yesterday to restore power to those customers, and to handle new outages caused by increased demand as people tried to stay cool after several hot days. Early in the day, several hundred customers at NStar and National Grid were without power, with those ranks decreasing as the day went on.

The outages, mostly in small pockets throughout the region, are not unusual in this type of weather, utility officials said. Issues often crop up at times of peak demand such as early evening, when people get home from work and crank up the air conditioning, turn on the television, and start cooking dinner.

“When the system is being pushed to its limit for several days in a row like this, we do expect to see some problems arise here and there,’’ said Caroline Allen, a spokeswoman for NStar.

Part of the problem in a heat wave, Allen and others said, is that transmission lines and cables have been worked hard for several days in a row, with little time to cool down. The problem becomes worse if temperatures remain high late into the night, when demand on the grid would typically drop.

Jerrold Oppenheim, a lawyer who advocates for low-income groups, said that though he knows communities have been without power, he hasn’t yet heard any complaints.

“Given the heat, I think we’ve been pretty lucky,’’ Oppenheim said.

“In this kind of heat, it’s horrible when you don’t have air conditioning or even a fan. And for people who are dependent for their health and safety on clean air or air-conditioned air, or even oxygen, in the most extreme cases, it can be devastating, catastrophic.’’

Calling the heat wave “very punishing,’’ Jim Owen, spokesman for the trade group Edison Electric Institute, said he anticipated a few outages, but hoped they were short-lived and as contained as possible.

“Nobody wants a power outage — whether it’s five minutes or five hours — least of all a utility company,’’ he said.

Last year, National Grid customers experienced an outage about once every 14 months, for an average of 106 minutes. That’s a drop from 2008, when outages occurred about once a year and lasted an average of 176 minutes.

NStar customers experienced an outage roughly every 15.6 months, lasting an average of about 83 minutes, in 2009. Previously, outages occurred about every 15 months but on average, lasted only about 76 minutes.

At NStar’s command center, workers monitor transmission lines around the clock. Some problems can be handled remotely, with a computer program capable of rerouting power around problem spots so that outages affect the smallest possible area.

Yesterday, Craig A. Hallstrom, vice president of electric field operations, surveyed the Big Board as he walked the floor of NStar’s emergency management center, where staff scanned computer data and took calls from customers reporting problems.

“When you think about it, these guys are the air traffic controllers of the transmission system,’’ Hallstrom said. “You’ll get an alarm. It will say ‘X’ breaker opened and you’ll get a light [on the board], and that’s the signal that something happened, and they’ll jump into action.’’

Erin Ailworth can be reached at