Safety Net Prevented a Wider Outage

The haywire power surge entered the lines about 8 a.m. after a simple human error by a crew at Pacific Gas & Electric’s San Mateo substation south of San Francisco.

Like a runaway train, the altered voltage surge rumbled north through the humming electrical lines toward one of America’s busiest cities, prepared to wreak its damage at every substation in its path--ruining equipment and potentially causing long-term disruption in electrical service.

What happened next, electric officials say, was nothing short of modern technological magic: A backup system kicked into place to automatically shut down 25 substations in the path of the abnormal surge.

The electronic safety net temporarily cut power to nearly 1 million people Tuesday, causing havoc throughout the Bay Area, but it averted longer-term problems and perhaps stopped the troubles from spreading farther into Northern California.

Scott Blakey, a PG & E spokesman, said: “The substations shut themselves down--all within the blink of an eye. Or two blinks.”

At a news conference Tuesday, Gordon Smith, president and chief executive officer of Pacific Gas & Electric, said the company’s safeguards effectively averted a disaster.

“It triggered a protective system that worked as it should have, that isolated the San Francisco Peninsula from the rest of Northern California.”

The backup system--a series of sensors that shuts down substations at the first hint of a damaging power surge--is among several methods employed by electric companies nationwide to minimize equipment damage and stop power problems from spreading after substation accidents.

A similar sensor system was used in 1996 when two power outages at major substations in Arizona and Oregon triggered a massive chain reaction of blackouts that sped through power companies serving cities across the West. In similar fashion, the sensors shut down a series of substations, but a much wider area was affected because the breakdown occurred at much larger substations.

Tuesday’s outage occurred when a crew wrapping up a construction project forgot to remove a pipe that was serving as a temporary ground for a bank of switches, Smith said. When power was turned back on, the mistake triggered a chain reaction that knocked two generators offline.

“These systems react in a heartbeat,” said John Ballance, manager of grid dispatch and operations at Southern California Edison in Los Angeles. “They have to--electricity moves at the speed of light.”

Ballance said his company has similar sensor systems that are continually upgraded to sense improper voltage more quickly and shut down lines. The sensors monitor electronic grids like sniffing watchdogs.

“With a surge like the one experienced by PG & E, if we protect equipment, then we can put things back into service quickly after isolating the problem, and people’s lights come back on. If we don’t protect the equipment, it takes us longer to put new equipment in place. And the lights stay out.”

PG & E spokesman Blakey said the 25 substations shut down by the safety system will have to be turned on by hand, a laborious process that kept electrical workers busy all day Tuesday.

“It’s a stately, measured process,” he said. “It’s not something you want to rush. It’s not like throwing a switch and all the power comes right on.”