Cable-test flub caused outage 

A widespread power failure was triggered Friday when an electrical worker improperly switched on a massive trans-Bay power cable, according to a company responsible for the infrastructure project.

The outage, described by PG&E as a “flicker” that lasted less than a second, affected electricity customers throughout San Francisco and on parts of the Peninsula.

Some customers reported losing power for minutes after the 11 a.m. blunder, but PG&E spokesman Joe Molica said the utility company did not detect any outages.

The flicker occurred when the Trans Bay Cable was improperly switched on by an operator during testing, according to Trans Bay Cable LLC spokesman P.J. Johnston.

The operator inadvertently skipped a step in mandated operating procedures, Johnston said, leading to a short-to-ground incident that shorted out PG&E’s local grid.

“It was like any other electrical short, only on a massive scale,” Johnston said.

Cable testing, which was suspended after the accident, resumed Wednesday using enhanced procedures to help ensure that the mistake is not repeated.

The cable was laid recently by a joint venture that includes private companies and Pittsburg.

The joint venture does not include PG&E, but the cable connects to the utility company’s grid at a PG&E-owned switchyard in The City’s Dogpatch neighborhood.

The $505 million Trans Bay Cable could deliver 400 megawatts of electricity into The City from power plants and other energy sources in Pittsburg once it’s fully operational.

It will be capable of delivering more power than the natural gas-fired Potrero Power Plant can generate, allowing the Mirant Corp.-owned polluting plant to be shut down this year if the cable proves reliable.

The cable also is critical for the planned CleanPowerSF program, which could see a team of companies compete with PG&E for power sales to residents and businesses within a year under California’s community choice aggregation

The Trans Bay Cable was not damaged by Friday’s incident, which occurred in a cable that connects the massive piece of infrastructure with PG&E’s Dogpatch substation, according to Johnston.

The Trans Bay Cable was scheduled to become fully operational in March, but it’s unclear whether that goal will be met.

“These critical months of testing are really important, so we’re going to do as much as necessary,” Johnston said. “This is a project that will be operating for 30 or 40 years or more.”


Delivering power

53 miles Length of Trans Bay Cable

10 inches Width of cable

2 Electrical transmission lines in cable

1 Fiber optic communication line in cable

400 Megawatts of power that can be transmitted

$505 million Project cost

40 Percent of San Francisco’s power needs that could be transmitted

Source: Trans Bay Cable LLC

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