Utility Knew S.F. Power Could Fail

Pacific Gas & Electric Co. has realized for years that its downtown power system was vulnerable to a failure like the one that occurred this month, the San Francisco Examiner reported.

According to the utility’s own documents, PG&E; foresaw that even a momentary citywide disruption could mean huge problems for downtown San Francisco because it would take hours to turn the system back on, the newspaper said.

Utility officials said Friday that the city’s downtown power system is designed like those in New York, Chicago and Baltimore to be far more reliable than the typical electrical distribution network. Yet, they acknowledged, it does have the drawback of being hard to restart if power is totally lost, which became apparent during the Dec. 8 outage.

“They’ve clearly known this could happen. It’s the way the network was designed,” said Bill Marcus, an economist with the Sacramento energy consulting firm JBS who has worked on numerous issues concerning PG & E. “They did all these things to prevent it from happening, but a new pathway to failure opened up.

“What this has pointed out is a weakness in the system that is likely to cause a rethinking of the costs and benefits of improving San Francisco’s power system,” he said.

But most experts agreed that spending the money to eliminate every known vulnerability of the power system would probably drive energy costs so high that customers would long for the days when power was cheap and they suffered an occasional blackout.

PG & E managers said no amount of money could protect the system from strings of freak occurrences like the combination of human and technological errors that recently knocked out San Francisco’s power.

On Dec. 8, a work crew at the San Mateo substation, which normally provides most of San Francisco’s electricity, failed to remove six grounding lines before restoring power to a piece of equipment that was under construction. When the power was switched on, a huge bolt of energy surged into the dirt below the equipment, causing a small explosion and instantly dropping the voltage in the transmission lines to almost nothing.

Then a set of protective relay devices, designed to stop electrical disruptions from going beyond the substation, failed. PG & E officials say they have not yet been able to figure out why.

San Francisco’s two generating plants--the city’s last line of defense against total power failure--had to shut themselves down to avoid damage.

“There is no 100% foolproof system,” said Rod Maslowski, PG & E’s manager for transmission planning and operation. “The question is: Do you spend hundreds of millions of dollars to prevent something that happens once every 20 or 30 years?”

Annual reports that PG & E filed with the state Public Utilities Commission in 1997, 1989 and 1983 outline vulnerabilities that have the potential to put San Francisco’s power system in double jeopardy.

First, because it has water on three sides, the city is reliant on transmission lines that follow a single path up the peninsula, opening the possibility that most of its power could be knocked out in one fell swoop.

Secondly, the design of San Francisco’s downtown power grid has the potential to prolong problems. It features 10 independent distribution networks that have to be turned on separately in the event of an outage, the reports said.