By Robert Tanner and Jim Krane
The Associated Press

Click to view map (PDF file) showing a detailed sequence of tripped transmission lines causing the blackout. (AP photo) | ZOOM |

Waves of power strong enough to run a mid-sized city swung wildly between the Midwest, New York and Canada. In Cleveland, the voltage dropped to zero "like a heart attack." In Connecticut, a chunk of the control room's wall of maps suddenly flashed green - no juice.

At a monitoring nerve center in Valley Forge, Pa., that oversees the tangle of transmission lines and substations from New Jersey to West Virginia, a huge field of electricity dropped out and drained north.

"It was so massive," says Phillip G. Harris, president of PJM Interconnection, which controls electricity in much of the mid-Atlantic region, describing the flashflood of electrons bursting the nationwide system of controls Thursday.

Engineers watching the power storm on their screens were as helpless to stop it as the people whose elevators jerked to a stop mid-floor in Michigan or whose subway trains ground to a halt in New York City.

Once it got rolling, the great blackout of 2003 swept from Ohio to Canada to New York City in the time it takes to recover from a sneeze, leaving millions in eight states and Canada suddenly without electricity on a steamy summer afternoon.

So far, the search to fully understand the string of failures that led to the biggest blackout in U.S. history has turned up broken alarms and an initial trio of failed high-voltage lines in Ohio owned by Akron-based FirstEnergy Corp. Investigators also are looking at the overall aging infrastructure of transmission lines, serving a technology-driven society of cell phones that snap photos and of talking computers, the stuff of science fiction when many of the towers and transformers went up decades ago.

The men and women at the control panels and computer screens - technicians and engineers and security monitors - watched it all happen. Investigators are turning to them, and the equipment they run, for answers.

Some workers had an instant of warning time. Others were blindsided, dumbstruck, incredulous.

Going, going ...

It's 4:05 p.m. EDT Thursday, and the system is wobbling. Utilities in Canada and the eastern United States see increasingly wild power swings as voltage flows first in one direction, then another.

"What we saw was small swings of our flow, our power flows to Ontario," says William Museler, president of New York Independent System Operator, a utility provider in upstate New York. "We were supplying Ontario with about 1,000 megawatts at the time this started. Those power swings started at about 100 megawatts. They went to 800 megawatts - ultimately went into the range of about 3,000 megawatts. When it got to that range, that's when the system became unstable."

One hundred megawatts is enough to power several huge auto plants; 3,000 megawatts is enough to keep the entire city of Tampa running.

It's 4:09 p.m. By now, power has begun to drop slightly in Cleveland - then it plummets.

"It happened to us so quick. The voltage was lower than we wanted and then ... boom! It just dropped," says Jim Majer, commissioner at Cleveland Public Power, a city-owned utility. "It was like a heart attack. It went straight down from 300 megawatts to zero."

The nation's electrical grid is balanced between power plants that pump out huge amounts of electricity and its power-thirsty consumers - cities, industrial plants, baseball stadiums, air-conditioned skyscrapers. When the grid works, individual failures seal themselves off so power keeps flowing. When it fails, the often tenuous supply-demand balance can spur massive surges one way or the other, shutting down substations and generators as they try to protect themselves from damage.

And that's just what happened Thursday.

It's now 4:10 p.m. In Newington, Conn., the nerve center at Convex - the Connecticut Valley Electric Exchange - is quiet. Then the lights dim and the room goes dark. The air-conditioning drops and there is a momentary pause. The utility's backup generator kicks in.

Everything goes wild in the control room, where Peter Brandien and three operators monitor a wall of lights that trace the electrical grid of lines and substations of Connecticut and western Massachusetts in red and blue - a "status board" 15 feet high and 48 feet long.

"This thing was so wacky. Your initial thought was 'Is this real?' " Brandien recalls. "The western part of Connecticut all turned green, and the whole board started flashing."

The phones begin to ring: Technicians from farther north in New England are calling.

Unhesitating, relentless, the blackout sweeps across the East; generators, substations and nuclear plants automatically disconnect in a daisy chain of split seconds. Millions of people see lights and computer monitors flicker, dim and go dark.

It's 4:11 p.m. The monitors on duty at PJM Interconnection, which operates the energy market from New Jersey to West Virginia, watch, stunned and disbelieving, as electricity drains northward.

"They saw it happen, and there was very little they could do to influence it," says Robert Hinkel, PJM operations manager. "An operator can't react in less than a second."

Amid the gloom, there is a bright spot: Automatic protections succeed in confining the blackout in PJM's coverage area to northern New Jersey and northwest Pennsylvania.

And other electrical systems manage to isolate themselves, too: Buffalo, N.Y., survives as an island of twinkling lights in the enveloping darkness.

The Ohio dis-connection

Now, as utility crews check transformers for damage and homeowners seek repairs for damaged electronics, investigators conduct the post-mortem, examining records of glitches buried in computer logs in the arcane language of mechanical switch behavior.

They are looking back to the hours - and days, weeks and months - before the catastrophe.

One warning sign already uncovered: The Ohio transmission lines suspected as the blackout's origin were buzzing with excess electricity earlier Thursday, causing trouble for their neighbors, says Pat Hemlepp of American Electric Power Co. in Columbus.

And on the shores of Lake Erie, hours before the blackout, a cloud of ash and a big whooshing sound spewed out of the three chimney stacks at FirstEnergy's Eastlake, Ohio, coal-fired power plant as it shut down. Why the 680-megawatt plant went offline is still not clear, but FirstEnergy spokesman Ralph DiNicola says the company is examining if it had any connection to the first of the transmission lines to go down.

The ash blanketed cars, homes and picnic tables in the village of Timberlake.

The town's mayor, Sam Santangelo, says the ash showers happen every now and then. And he should know: He lives no more than 1,000 feet from one of the stacks.

But with the power going out soon after along the lake, and then the massive blackout, he adds, "It makes you wonder."