Baltimore Gas and Electric Co. officials blamed Wednesday's power failure, which left about half the homes in Harford County without electricity for much of the day, on "the perfect storm."
With a 3-foot length of power cable nearly the diameter of a baseball in hand, Kenneth W. DeFontes Jr., vice president of electric distribution and transmission at BGE, told County Executive James M. Harkins and members of the county's legislative delegation Friday that the outage was the result of a fluke event called "galloping conductivity."
DeFontes said ice formed on two high-voltage power lines, making them act like airplane wings that lifted the cables.
He said the high winds, which were perpendicular to the power lines, started moving the cables back and forth until they started spinning like a jump rope.
The spinning motion brought the wires into contact and shorted out the main source of power to about a half-dozen substations serving the county.
Lights went out in nearly 70,000 homes, businesses, hospitals and government offices throughout the county shortly after 1 p.m. Some customers didn't get power back until about midnight.
"In my 32 years with the company, I have only seen it happen one other time," DeFontes told the county officials during their delegation meeting Friday morning. "That was 20 years ago."
He showed the county officials a video of a similar event that occurred in the past.
DeFontes said the cables that came into contact Wednesday were stretched over water. No trees were nearby to slow the high winds.
In answer to a question from a delegate, DeFontes said the power failure arose from of an extremely unlikely set of circumstances, but he could not guarantee that it would not happen again.
To help prevent it from happening again, he said the utility would wrap the cables with a covering called "a spoiler." He said this would change the shape of the wire and help prevent it from developing the lift needed to start spinning.