Failure of Major Backup System May Have Exacerbated Bay Area Power Outage

SAN FRANCISCO —  Last week’s Bay Area power blunder was traced to human error, but some experts say it was exacerbated by Pacific Gas & Electric Co. system breakdowns.

What started as a minor incident Tuesday ballooned into a full-blown emergency within milliseconds, leaving about a million people powerless in San Francisco and San Mateo counties.

Although a construction crew was directly to blame, regulators say it appears the outage was intensified by several factors, including the apparent failure of a major backup system, designed to carry the electrical load if San Francisco lost its main transmission lines.

Experts believe the outage spread farther and lasted longer than it should have, the San Francisco Examiner reported.

And even after San Francisco regained power, it was in imminent danger of going dark once again because of problems in distribution lines. To compensate, officials briefly turned off power to thousands of customers in Daly City.

“Good industry practice would have localized the failure to the circuit where it occurred,” said Tom Green, an industry automation consultant who has worked for utilities throughout the Western states. “It is surprising that something simple could cascade so far. It reflects back to poor protection designing. There was a weakness somewhere that would allow one failure to trigger so many failures.”

PG&E; officials, embarrassed and apologetic, acknowledge that they don’t know whether their system functioned properly. A preliminary report should be completed next week.

“It’s amazing. Within one second, the city was completely dark,” said Bill Blastic, PG&E;’s manager of distribution. “That one second has literally thousands and thousands of possibilities that need to be looked at.”

Relay by relay, circuit by circuit, the utility is probing for breakdowns that may have contributed to the debacle.

A primary focus is PG&E;’s “protective scheme,” intended to safeguard equipment while limiting the spread of power failures.

“The system was designed to shut down when you have voltage instability,” Blastic said. “Given the nature of the fault and its location, I’m not sure our equipment operated appropriately or not appropriately.”

The crisis began at the San Mateo substation when utility workers mistakenly left a grounding rod in place during routine field work. When electricity was turned back on, power surged directly into the ground, triggering near instantaneous failures at 64 other substations and knocking out San Francisco’s two power plants.

Hospitals were forced onto generators, public transit came to a standstill, and flights were delayed at San Francisco International Airport. During the blackout, which started at 8:15 a.m. and continued in spots for nearly eight hours, a 75-year-old San Francisco woman was killed by a hit-and-run driver who didn’t stop at an intersection where the traffic lights were off.

The blackout was expected to cost the utility millions of dollars in consumer claims. So far, about 3,300 claim applications have been requested.

“We sure regret the need to have to do this, both the inconvenience on the customers as well as the hit we have to take,” Blastic said. “It’s our money basically. This is not customer money. This comes from our earnings.”