The first rolling blackouts in California since the power crisis of 2001 were caused by a faulty sensor at a new power transfer station in Sylmar, raising concerns about how such a relatively minor glitch could leave nearly 500,000 customers without electricity.
The $118-million facility, operated by the Los Angeles Department of Water and Power, was opened with much fanfare last fall. But officials now believe a malfunction in a sensor that monitors a cooling system at the station triggered an automatic shutdown Thursday afternoon.
The resulting blackouts underscored the fragility of the state's power grid. Experts said the incident showed once again that California doesn't have the power plants or the transmission capacity to reroute electricity when a major transmission line goes down. California is particularly dependent on power generated outside the state -- especially during the summer, when customers crank up air conditioners.
"We have a fragile system in California, and we have more people moving to this state," said Anne Silva, a spokeswoman for San Diego Gas & Electric, which was forced to cut power to more than 51,000 customers for nearly an hour. "When we rely on just a few transmission lines in the state, and something happens, then it kind of has a domino effect."
Officials at the DWP spent Friday urgently working with the manufacturer of the equipment, ABB Inc., to determine why the sensor failed and to prevent a recurrence.
This is crucial, said Henry Martinez, chief operating officer of power for the DWP, because the same type of sensor is used in other power-distribution equipment.
"We've got to get this fixed to make sure this doesn't happen again," Martinez said.
The malfunction occurred at the Sylmar Converter Station, the terminus of one of California's major north-south electric transmission lines. The facility is where Southern California receives electricity from power plants in Oregon, Martinez said.
At the Sylmar facility, electricity is distributed to local electric grids that deliver it to homes and businesses throughout Southern California.
Martinez said that at 3:45 p.m., a malfunctioning sensor signaled a problem in the cooling system of a transformer, and that automatically shut down one of the station's two main converters, which forced officials to temporarily shut down the entire facility.
