Canadian Consulting Engineer

Power outages prompt questions about transmission lines

January 6, 2015

Severe winter storms that hit across Canada at the beginning of the New Year have caused power outages and prompted memories of the momentous ice storm that occurred in 1998 in Quebec and Eastern Canada, as well as the one that crippled Toronto last year.

Early this week in British Columbia, a heavy snow storm saw up to 50 centimetres of snow fall in the Okanagan Valley and around Kamloops, resulting in power outages for 14,000 of BC Hydro’s customers. The same weekend in Quebec 155,000 households were left without power on Sunday, January 4.

While in both the above cases the supply was restored relatively quickly to most customers, that was not the case in 1998. The great ice storm felled hundreds of high-voltage transmission lines leaving huge areas without power for weeks, causing deaths and widespread hardship. The disaster affected a million homes, as well as farms and industries, and cost an estimated $5 to $7 billion.

After this week’s storm outages media reports were questioning again why more cities have not buried their power distribution lines below ground, where they would be safe from falling tree branches. Most power outages occur when tree limbs become weighed down with snow and ice, then break and fall on the lines.

However, in a CBC report dated January 5, Tom Adams, an independent energy expert, pointed out that burying cables is not a panacea. The cost of burying the lines would make energy distribution 5 to 10 times more expensive, he said. Also, buried lines can be vulnerable to flooding, and finding and detecting problems with the lines can take time and can be expensive to repair.

“Except for tunnelling contractors, I don’t think you could find anybody who would support some kind of massive conversion to undergrounding,” Adams said

After the 1998 ice storm, Quebec Hydro has re-engineered its transmission system to better withstand heavy ice loads and has adapted the network routes to make the system more flexible. Some of the utility’s transmission lines bring power thousands of kilometres from hydroelectricity generating stations in the north. One in 10 transmission towers are now designed to be more robust with stronger foundations and structures to avoid the cascading tower effect. Other towers are designed to be sacrificed if necessary to keep the lines open.

To read the CBC report of January 5, click here.

To read a report in the Montreal Gazette on January 5, click here.

To read a CTV News report of January 5, click here.


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