By Pat Loeb

By Pat Loeb

PHILADELPHIA (CBS) – After an event like the ice storm, you might wonder, why are power lines on top of utility poles where they’re so vulnerable to falling tree limbs?

There are a couple of reasons; one is historic, according to overhead power line expert Steve Corfidi, “electrical infrastructure was developed back in the early part of the 20th Century.” Technology at that time didn’t exist to safely place high voltages underground.

Back then, lines were even more vulnerable. “Electrical structures today are a bit stronger than those put up more than a hundred years ago.”

He says today’s lines carry higher voltage which means fewer wires. “You can space those fewer wires farther apart so that if a tree limb were to drop onto a line it doesn’t necessarily cause a short circuit by forcing two wires together as easily.

Corfidi says, even when the technology was developed, it did not resolve problems with outages, something PECO spokesman Kathy Menendez can vouch for, “Customers with underground service in front of their home and aerial service experienced outages during this storm.”

Menendez says about 40 percent of PECO’s lines are underground. They were untouched by tree limbs but not by other hazards, such as “A lot of snowfall and a lot of rainfall. As the moisture seeps through the ground, that can tend to cause outages for underground service.”

Menedez says that takes even longer to repair because it’s harder for crews to get to.

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