Power Briefly Knocked Out for 232,000 Customers : Electricity: Failure of a circuit breaker or a cable fault are suspected. The outage affects workers, shoppers and motorists.

A 45-minute electrical failure struck the San Fernando Valley on Friday evening, blacking out 232,000 customers in an area from Burbank to Tarzana, briefly snarling traffic, troubling airport traffic control and stranding high-rise office workers in stalled elevators.

The outage, which began about 5 p.m. was caused by an undetermined equipment failure, which prompted an automatic protective shutdown of power at DWP stations in North Hollywood and Van Nuys, said Dave Mahoney, assistant manager of power operations for the Los Angeles Department of Water and Power.

It shut off service to 142,800 customers in Van Nuys, North Hollywood, Sherman Oaks and Encino, said DWP spokeswoman Debra Sass. Meanwhile, about 90,000 customers in neighboring Burbank lost power in a domino effect from the North Hollywood problem, said Dennis Moran, power production superintendent for the Burbank Department of Water and Power, which is linked to the DWP grid.

Power was restored by 5:43 p.m. to all but 5,000 customers in Sherman Oaks near Mulholland Drive; their power was restored by 7 p.m., Sass said.

“It was a widespread outage, and there were a lot of customers affected,” Sass said. “But luckily it didn’t last for too long.”

If the automatic shutdown had not occurred, “people would have been in the dark a heck of a lot longer,” Mahoney said.

Lights flickered and computers shut down momentarily in the downtown and West Los Angeles areas in a spillover effect from the sudden loss of power in the Valley, the DWP said.

The outage was caused by a fault in either a large circuit breaker or an underground cable at an electrical receiving station in North Hollywood, which cut the flow of power to another receiving station in Van Nuys and to Burbank, Sass said.

The cause of the fault was under investigation, Sass said.

The outage forced the Burbank Airport to temporarily rely on emergency generators, spokesman Michael Green said. But no flight delays were reported at Burbank or Van Nuys airports.

However, the radar system at Van Nuys Airport remained out of service after power had been returned, said Officer Milton Cox, of the Van Nuys Airport police. The cause of the failure was unknown.

Traffic officers were dispatched to about 50 intersections, mostly in Sunland, Van Nuys and North Hollywood, to relieve traffic congestion, the City Bureau of Enforcement and Intersection Control said. There were no reports of accidents caused by the outage.

The Los Angeles Fire Department received 50 reports of automatic burglar alarms sounding and of people stranded in elevators, but no injuries were reported, spokesman Jim Wells said. The return of power freed all the stranded passengers, he said.

Hospitals that relied on backup generators for about 30 minutes during the outage included Thompson Memorial Medical Center in Burbank, Hollywood Community Hospital in Van Nuys and Tarzana Regional Medical Center in Tarzana, hospital officials said.

When the power went out at the Sherman Oaks Galleria, security guards and merchants ushered shoppers out of the mall. But many of the merchants could not leave, because steel security gates could not be dropped in front of their stores without power.

“They closed the mall down, but we had to wait because we couldn’t secure the store,” said Chris McKinney, an employee of the Florsheim shoe store.

Power was off for about 20 minutes at the Galleria. In the words of Christine Blow, an employee of Helen Grace Chocolates Store: “It lasted about three cigarettes.”

Mall security employees stood guard on jewelry stores until power returned. One of the stores was Jewelrymania, where saleswoman Ilissa Gerstenhaber said employees moved a display case of watches inside and remained in the store because they could not shut its electrically operated security gate.

The mall began filling up again with customers within half an hour after the blackout. Some stores in the mall and also on Ventura Boulevard did not reopen after power was restored because the employees had gone home for the day.

Shopping was also disrupted at Sherman Oaks Fashion Square, which closed for about 15 minutes, said Petite Bouyer, an administrative assistant to the mall’s management.

Times staff writers Eric Malnic, Bettina Boxall and Stephanie Stassel contributed to this story.