TORONTO- Utility crews have been busy over the past couple of weeks working to restore power to thousands of homes across the GTA. The culprit in most of these outages has been a single hydro pole fire. One pole fire can affect power for tens of thousands of residents in a given community.
The odd thing is, these fires happen when we get rain or drizzle in the winter months.
The unlikely contributor is the road salt we use to melt snow and ice.
John McClean is the Vice President, Operations at Power Stream, which serves municipalities in the 905 and 705 regions, and said the fires happen every winter when “we get an accumulation of contamination on the insulators that carry our conductors – typically salt contamination.”
Normally, McClean’s crews would be washing the salt off the poles but they can only do that when the temperatures warm up above minus 5 degrees Celsius. We didn’t get anywhere near that temperature through January and February so the salt built up in the insulators.
When the temperature finally flirted with freezing, we got rain and drizzle. Mix the water with the salt and you’ve got a nearly perfect conductor. It means the current finds its way into the grounded pole. But the pole is a poor conductor, so it acts like the element in your oven. It resists the current, stores the heat and it combusts.
And you’re wondering how that road salt gets all the way to the top of that hydro pole.
McClean says the salt gets kicked into the air by passing traffic. But he and his team have noticed an increase in pole fire incidents since the province and municipalities have started using a salt solution brine to deal with icy roads.
“(Crews) do a pre-treatment before any type of snow falls and that allows the snow to melt and, particularly along high speed areas, it just gets kicked up into the atmosphere”
The brine used by Toronto’s Transportation Services is a salt water solution with a 23 per cent concentration. City staff estimate crews use an average of 2.3 million litres of brine every winter.