Extent of pole collapse from ice load surprises NB Power

NB Power managers and engineers are trying to sort out whether a surprising collapse of hundreds of power poles in the Acadian Peninsula following last week's ice storm was an anomaly or something that will demand stronger and more expensive infrastructure.

It's not clear yet which side of the debate is winning.

This is a massive decision.- Gatan Thomas, NB Power president

"We are having some discussions and, you know, we had them a few years ago and we're working on this," NB Power president Gatan Thomas said Mondayafternoon.

"This is a massive decision and we have to know how many times we're going to have these kind of storms before you make the decision."

NB Power owns more than 351,000 wooden utility poles that carry power lines to communities around the province. According to the utility, the average pole is about 17 years old and would costalmost $400 each if bought new today. With the exception of large trees and branches falling on power lines, they have enjoyed a low failure rate in recent years.

Caught by surprise

That's why collapse of so many last week caught the utility by surprise.

Thomas acknowledged it took a number of days to realize the extent of the failures, and eight days into the event the utility was estimating the number of poles that came down at between 350 and 400.

The wholesale collapse has slowed power restoration efforts considerably in northern communitiesleaving thousands of residents in the Acadian peninsulawithout power for more than a week.

NB Power insists there was nothing deficient in its equipment or engineering that caused the problem, instead emphasising the uniqueness of the storm to explain what went wrong.

"This storm brought ice that coated our equipment four times thicker than the most robust [Canadian Standards Association] standard well beyond the design of our equipment but also well beyond the CSA standard required for any weather region of Canada," NB Power said in a statement on its websiteTuesday.

"This was an extreme weather event."

Thomas said the fact more poles stayed upright than fell over shows him there is no fundamental problem with the equipment.

"I have no concern about that," he said. "The infrastructure actually proves to me that the infrastructure is meeting more than its design, because we have thousands of poles that stayed up and the ice loading was above, way above, the design."

NB Power is worried that strengthening the distribution system won't be worth the cost if severe ice storms remain rare events.

Options exist

Options to bolster the system include erecting poles closer together than the 60-metre distances now preferred and using thicker and sturdier Class 3 poles, rather than the Class 4 and 5 poles mostly in service now.

Another solution being tried by other jurisdictions that deal regularly with ice storms is to inject steel poles into the distribution system.

In Kansas a series of damaging ice storms in the early 2000s that brought down thousands of poles persuaded CMS Electric Cooperative in Meade to begin installing one steel pole for every nine or 10 wooden poles to limit the size of failures.

CMS general manager Kirk Thompson says steel poles are expensive, but once wooden poles begin to fall they pull on each other and can collapse in large, cascading groups.

"The worst one I saw there was 24 miles [400 poles] on the ground," said Thompson. "There wasn't a pole standing."

He has high hopes the intermittentsteel poles will keep the lights on in an ice storm.

"Basicallyit's going to have to bend.A wood pole breaks."

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Someutilities in the United States also reinforce selected poles with cables and anchors to try tointerrupt a group collapse.

But Thomas says the last major pole collapse he's aware of in northeastern New Brunswick was during a prolonged ice storm in January 1956.

The province lost several thousand poles in that event, including about 800 on the Acadian Peninsula, accordingto press reports, and Thomas is not sure spending money to defend against rare icing eventsmakes sense.

"We would have to significantly increase the design to be able to overcome a storm of this magnitude," said Thomas.