Saturday’s power outage may have been caused by road salt

UPDATE: Here’s a statement from Rebecca Hickey in Hydro Ottawa’s media an public affairs department:

The outage on Saturday March 14th affecting Stittsville, Kanata, Richmond and Munster was caused by a Hydro One pole that caught fire. The pole, located along Highway 417 near Huntmar, is the main source of electricity from Hydro One’s provincial high-voltage transmission grid to the local grid managed by Hydro Ottawa.

Pole fires can take place, particularly in late winter, when salt spray from passing cars builds up on the electrical infrastructure. This build up, paired with moisture in the air, can allow the electricity to travel through the insulator and energize the wooden pole, causing it to catch fire.

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The power outage that cut hydro to 12,000 customers on Saturday may have been caused by a pole fire due to road salt.

If it was indeed a salt build-up plus moisture that caused a fire, how does that happen? Here’s an explanation from PowerStream.ca, a power company in Southern Ontario:

Poles that are most at risk are located in high-traffic, high-speed areas, such as along the 400-series highways… 

Over the course of the winter, road salt residue and other contaminants accumulate on the ground, on hydro poles and on the equipment attached to them, such as line insulators, which prevent electricity from traveling from power lines to the pole.

When the temperature hovers around the zero degrees Celsius mark, the buildup of road salt residue, combined with the presence of moisture, creates an environment that can give rise to pole fires.

During spring thaws, accumulated snow and ice begin to melt and the moisture mixed with the road salt allows electricity to be conducted from the power line along the insulator and onto the metal bolt attaching the insulator to the pole.

The metal bolt heats up and if the surrounding wood is dry enough it begins to char and could catch fire. Poles can be severely damaged during fires, and the fire has to be extinguished before crews can repair or replace the pole and restore power to affected customers.


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3 thoughts on “Saturday’s power outage may have been caused by road salt”

  1. Hmmm….I find that a scary explanation. The bolt will only get hot if it becomes part of the path to ground. Being that salt, or the ions in it improve the ability for moisture or water to conduct electricity one would think that the bolt would be installed in a non conductive sleeve, possibly rubber when attached to the pole to prevent this. Especially along areas where it is indicated this can happen.

    I would also think that since this appears to be a known issue, that preventative maintenance would be performed to remove the build up of salt on equipment to prevent this from ocurring.
    It is one thing for some equipment to fail, it is another for a pole to snap. We are lucky that the sudden change in stress on the adjancent poles did not cause them to snap as well causing a much bigger issue that could have also become very dangerous.

    1. Thanks for your comment Greg. I’ve asked Hydro Ottawa for more info about how this happened and if salt/moisture was indeed the cause.

      However, the road salt issue has caused a number of power outages – do a search for “road salt hydro poles” and you’ll come up with several incidents like this one. I do recall hearing something on the news a couple weeks back that hydro crews were doing some kind of preventative maintenance/cleaning on hydro poles near highways.

  2. Okay, so this is known to happen. Fair enough. So then you build in some redundancy so that a single failure doesn’t cause an extended outage. Basic analysis – plan proactively. So why doesn’t that seem to be in place? That is what annoys me.

    Sure this time it was only 4 hours of outage. But if this had caused 2 or 3 poles to need replacement, would there have been options to avoid an extended outage?

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