News Staff
Canadian Press
August 15, 2003

The electrical power grid is like a rope linking a team of mountain climbers. On a good day, someone slips and is hauled to safety. On a terrible day, someone slips and pulls everyone off the mountain.

Thursday was a terrible day for Ontario and the northeastern United States.

The grid is a web of transmission towers, power lines and computers linking generators to distribution centres and, eventually, to that air conditioner in your window.

Jim Haynes, a vice-president of Newfoundland and Labrador Hydro, calls it the biggest machine in the world.

Norm Rubin of Energy Probe in Ontario says the grid has saved the day countless times by allowing power companies with shortages to make up their needs from others who have surpluses.

"There is safety in numbers or interconnectedness – most of the time," he said. "The grid has saved Ontario from blackouts."

The public doesn’t notice when it works. They do when it fails.

The grid is incredibly complex. Alternating current surges through the system at 60 cycles a second, all synchronized and in harmony like an orchestra.

Computers struggle to match supply with demand, while keeping power loads at safe levels. Generators are brought on line or shut down as demand peaks or ebbs.

When something goes wrong, as it did Thursday, the rope can pull the climbers off with frightening speed.

At about 4:10 p.m. EDT on Thursday, the system was humming along, with engineers preparing to bring up more power to drive rush-hour subways and meet the demands as people got home from work, turned up the air conditioning, fired up the stove and clicked on the TV.

Something, somewhere – no one has pinpointed the culprit – went wrong. A generator fell off line. A transmission line failed.

The system surged and tension built up on the rope. All the intricately balanced factors began to clash. At this point, though, the event should still have been isolated. Somehow, it wasn’t and a dreaded cascade began.

"Lines are going to fail, plants are going to fail, that happens every day," said Mr. Haynes. "It’s why did it cascade to such a big event?"

Machines began to act automatically

"All this equipment is designed to protect itself," Mr. Haynes said. "They go into, ‘I don’t care what’s happening in the outside world, I’m tripping to protect myself.’"

Along the line, circuit breakers tripped and fuses blew to take areas off the grid and protect equipment from the suddenly unstable flow. Each of these caused more ripples along the grid – one more climber falling.

Mr. Haynes described the events: "More load and then there’s an overload somewhere else, a line is tripped you get generators going out. In a matter of two or five minutes, even seconds in some systems, it’s all flat."

Technicians at generating stations – coal and gas-burners, hydro dams and nuclear plants – watched the demand levels fall as segments of the grid tripped out. They had power coming out with nowhere to go and they killed the generators. The nuke operators shut down their reactors.

Within seconds, much of the northeast U.S. and most of Ontario was down. The whole team fell off the mountain.

With the system shut down, the problem became one of getting the lights back on.

It isn’t just a matter of throwing a switch, Mr. Haynes said. Everything must be resynchronized.

He likened it to a homeowner who plugs in one appliance too many, trips a circuit-breaker and then simply resets the breaker without taking something off the line.

"By the time he’s back upstairs, the breaker’s gone again. You’ve got to take something out of the circuit. The power system’s no different."

There’s another problem. Coal- and gas-fired stations take time to get steam up and generators turning if they’ve cooled down.

Mr. Rubin said Ontario’s nuclear plants, which provide more than a third of the province’s power, take 36 hours to restart after a shutdown.

Once the power comes back, the questions begin. Is the grid obsolete? Is it the victim of stinginess? Is there new technology available that would prevent a recurrence?

Maybe, but that’s impossible to answer until the cause is traced and it will be a long post-mortem.

"There will be a lot of engineering reviews of this particular situation, how it happened and what happened," Mr. Haynes said.

"It’s not only the root cause. The root cause may have been a transmission line that failed. The question is, if that failed, that’s okay . How come everything else happened?"