O.C. Transformer Blast Hurts a Rare Victim

Transformer explosions are not uncommon, but it’s rare for a passerby to be injured, experts said Tuesday, the day after a 30-foot column of fire leapt from an underground vault near Fashion Island.

The 7 p.m. accident left a 33-year-old woman with second- and third-degree burns and cut off power to the bustling Newport Beach shopping center for 40 minutes.

Noting privacy rules, Newport Beach firefighters declined to name the victim. Monday night, she was reported to be stable at Western Medical Center-Santa Ana.

It may take weeks to determine the accident’s cause, said Southern California Edison spokesman Marlon Walker.

“I don’t know the specifics of what caused this,” Walker said. “But it’s an electric device and, like all devices eventually do, it failed.”

The incident knocked out power to 220 customers, Walker said. Fashion Island opened Tuesday morning with no problem, a spokeswoman said.

“Since the incident was so close to the end of the shopping day, it really minimized the sales effect on our businesses,” said spokeswoman Shayne Voorheis. “That was the plus, if there was any.”

Transformers convert high voltage into usable electric current and are often placed in vaults -- small, closet-sized concrete rooms that also house electric power connections and switching equipment -- about 10 feet underground.

While not knowing what went wrong with the Newport Beach transformer, experts said such malfunctions are more frequent during low temperatures or rain.

Cold weather creates a strain on the equipment, which can cause it to overheat, said Mark Shirilau, an electric power systems expert and former Southern California Edison engineer. This, in turn, can cause sparking and short-circuits, especially when it’s raining. The heat also can raise air pressure inside the vault, with sometimes explosive results if a fire erupts.

Expanding and contracting parts inside a transformer can loosen wires, which can cause mechanical failure and an explosion, said Shirilau, who is now president of an Irvine engineering consultant firm.

Compounding the problem and probably causing the massive flames in the Newport Beach incident is the fact that transformers are cooled with oil, he said. A special kind of oil is used as a coolant in transformers because it doesn’t conduct electricity and is not as corrosive as water, but in rare cases can ignite if the system malfunctions and the electricity heats the oil enough to turn it into an explosive gas.

For example, in November 1997, a 50-pound metal cover rocketed 50 feet up at a West Hollywood apartment complex when a transformer exploded under the front lawn. No one was injured.

Those hurt when transformers malfunction are usually electrical workers. In 1990, three such workers were killed in Pasadena during an explosion in a concrete vault that contained a 4,000-volt power line. In September this year, a maintenance worker in Tampa, Fla., was electrocuted after apparently failing to follow safety procedures.