(Adds power still out for many, comments from expert)
By Alexandria Sage and Noel Randewich
SAN FRANCISCO, April 21 (Reuters) - A power outage triggered by a fire in a utility substation blacked out much of San Francisco on Friday, paralyzing the city's technology and finance center, halting its famed cable cars and shuttering major retailers.
The utility PG&E Corp reported a fire and a circuit-breaker failure at a San Francisco substation, with a series of outages hitting the Bay Area city shortly after 9 a.m. (noon ET/1600 GMT) and ultimately cutting power to some 90,000 customers.
Office workers in the city's financial district spilled out onto the sidewalks, wandering the streets in search of an open cafe, or stood waiting in the lobbies of their buildings as elevators came to a stop. "It's pretty big, seems like half the city has no power," said King Lip, chief investment officer at Baker Avenue Asset Management in San Francisco. "We were in the middle of a trade."
Fourteen neighborhoods were affected, including the main shopping district near Union Square, where stores and coffee shops turns signs to closed and major retailers such as Macy's and Louis Vuitton shut their doors.
In a city proud of its technological prowess, the outage forced residents back to the dark ages. At the salad bar chain MIXT downtown, cashiers took credit card payments using old-fashioned paper imprints, as customers lined up to eat in the dim natural light.
"Old school," commented patron Ben Fackler. "I haven't seen that in forever."
DARKENED BY ONE SUBSTATION
By 3 p.m. electricity had been restored to less than a third of the affected customers and PG&E spokesman Paul Doherty said that it would be several more hours before the rest would be brought back online.
"Workers have entered the substation. They're assessing the damage and starting to make repairs,” Doherty said.
San Francisco International Airport remained operational, and the U.S. Department of Homeland Security said through a spokesperson that the agency had not received any reports indicating that the outage was related to any security or terrorism incident. The spokesperson requested anonymity, citing department policy.
"This had nothing to do with cyber," said Joe Weiss, an expert on control system cyber security who has testified to Congress about structural weaknesses in grid components.
"The real question is how could one substation take out, effectively, San Francisco? What other failures occurred there that didn’t isolate this?"
Wells Fargo & Co closed 13 bank branches and four office buildings, while the New York Stock Exchange said its ARCA options trading floor in San Francisco was briefly unavailable because of the power outage.
For more than two hours, trains streamed through the Montgomery Street station as the outage prevented them from stopping until backup generators came on line at about 11:30 a.m., Bay Area Rapid Transit said.
At Saint Francis Memorial Hospital in the Nob Hill neighborhood, all non-essential appointments and procedures had been canceled, spokeswoman Blair Holloway said.
Two of four campuses of Sutter Health's California Pacific Medical Center were also impacted by the outage, spokesman Dean Fryer said. Elective surgeries were canceled and emergency patients were directed to other hospitals, Fryer said. (Additional reporting by Heather Somerville, Jeffrey Dastin, Joe Menn and Noel Randewich in San Francisco, Rodrigo Campos in New York, Tom James in Seattle and Nichola Groom in Los Angeles; Writing by Sharon Bernstein and Dan Whitcomb; Editing by Mary Milliken)