Quebec ice storm: Why it's impossible to storm-proof the power grid

Energy producers have taken lessons from the Great Ice Storm of 1998 to make the power grid more reliable, but they’ve also resisted some of the more costly ideas, such as retrofitting entire cities with underground cables.

At the peak of recent Quebec blackout, 155,000 homes were without power

Contact between trees and power lines is one of the key factors in power blackouts. (Matthew Sherwood/Canadian Press)

The ice storm that left an estimated 155,000 Quebecers in the dark this weekend had echoes of the Great Ice Storm of 1998, which left millions of homes in Eastern Canada without electricity for weeks.

This time, power was restored relatively quickly – within 12 hours for the majority of Quebecers – which reflects some of the lessons hydro-electricity producers have taken from the 1998 blackout to make their power grids more reliable.

At the same time, however, they have also resisted some of the more costly ideas from the Great Ice Storm, such as retrofitting entire cities with underground cables.

"I think the industry recognizes that perfect reliability is unaffordable," says Tom Adams, an independent adviser and researcher in the energy sector.

Current estimates are that it would cost five to 10 times more to distribute electricity to a big city via underground cables, and that not all of nature's problems would be alleviated even if that were done.

While much of Canada has been facing extreme weather in recent days, residents of southern Quebec experienced rain followed by freezing cold, which led to ice forming on trees and caused many large branches to snap and fall onto roads and power lines.

These sagging branches and broken electrical lines led to massive power outage, although Hydro-Quebec reports that more than 98 per cent of affected customers had their power back within the first 12 hours.

While challenging, the storm was nowhere near as devastating as the Great Ice Storm of 1998, in which millions of homes across Eastern Ontario, Quebec and parts of Nova Scotia lost power, some for weeks. At least 25 people died in Canada, most of hypothermia.

The devastation even led to the deployment of Canada's military to ensure public safety, and the total economic costs of the 1998 storm were estimated to be between $5 and $7 billion.

Cascading towers

In any storm, the two aspects of the grid that are most affected are transmission lines, which are the high-voltage lines that travel into and between cities via massive towers; and distribution lines, which are the lower-voltage lines that move from street-level utility poles to individual homes.

The 1998 blackout in Quebec and Eastern Ontario was largely caused by ice on transmission lines. The ice build-up was so significant that it caused 300 transmission towers in Quebec and another 50 in Eastern Ontario to topple, says Adams.

After the '98 storm, Hydro-Quebec resolved to build its transmission towers to higher engineering standards. That included pouring a larger foundation for each tower, using thicker transmission wires and making every 10th tower along a transmission line a so-called "anticascading tower."

When the towers collapsed under the weight of the ice in 1998, "they tended to pull a lot of adjacent towers down," says Jim Burpee, president and CEO of the Canadian Electricity Association, which represents power producers across the country.

He says Hydro-Quebec changed its infrastructure so that "you could sacrifice, if I could use that word, a tower, and it collapses early and the rest of the towers don't collapse, or not as many collapse. So you reduce the amount of damage that you have."

Underground lines

A lesser problem in 1998, but a key cause of the recent blackout in Quebec as well as the one in Toronto in 2013, was the effect of ice-encrusted tree branches falling on residential power lines.

A report released in the wake of the Toronto blackout recommended the city look at trimming more of its tree cover.

Since 1998, Hydro-Quebec has enhanced its tree maintenance program, and now spends about $60 million a year on it, says Hydro-Quebec spokesman Serge Abergel.

"It's impossible to remove all of the trees," he says, acknowledging that "nobody wants to live in a treeless neighbourhood."

But given the danger trees pose to electrical lines — and vice versa — some observers have suggested that the solution is simply to bury the lines underground.

Images of falling power lines in Quebec this past weekend reminded many of the Great Ice Storm of 1998. (CBC)

Adams says "undergrounding" is prevalent in many new housing developments, where power lines can be laid at the same time as sewer, water and natural gas lines. But it's by no means a cure-all.

Buried power lines may be protected from ice and pesky tree branches, but they are more vulnerable to flooding. Like overhead lines, they're not immune to more general equipment failure — and when a problem does occur, it can be harder to identify and repair.

Not only that, but the U.S. Energy Information Administration estimates that underground power lines can cost up five to 10 times more than overhead distribution lines.

Adams says that retrofitting a major city such as Toronto or Montreal to underground power lines is "insane."

"Except for tunnelling contractors, I don't think you could find anybody who would support some kind of massive conversion to undergrounding," he says.

"It's simply a cost issue."


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