The science behind the salty towers causing Nova Scotia power outages
Dalhousie University professor explains how salty air can redirect electricity to the ground, killing power
When the electricity went out in the province earlier this month, Nova Scotia Power blamed a familiar foe.
Outages this morning were largely caused by salt contamination on electrical equipment. This is an issue for all coastal electric utilities. With the warmer temperatures and moisture in the air this morning, this has caused electrical arcing leading to outages. <a href="https://twitter.com/hashtag/nsstorm?src=hash&ref_src=twsrc%5Etfw">#nsstorm</a>—@nspowerinc
The power company has been blaming salty towers for at least twelve years, but can the ice-melting mineral really turn out the lights?
Some people were skeptical.
I mean that’s pretty good. In Nova Scotia, the power would go out if someone looked at a transformer the wrong way. That and salt fog.—@ZobeeWanKenobi
- A cold winter wind blows salt onto its equipment over a period of hours or days.
- The temperature rises, adding moisture to the air.
- That moist air causes arcing, which is when an electrical current discharges from transformers or wires as bright light or sparks and sounds like buzzing or crackling.
- The arcing causes a power outage.
CBC News phoned Mohamed El-Hawary, a professor of electrical engineering at Dalhousie University, to test the claim.
"Our worst enemy is the salting of the roadways in the neighbourhood of the transmission towers," he said.
Routes near the briny sea greatly increase the problem.
El-Hawary said if you look up at power lines, you'll see the conductor lines, which are strung between towers, hanging from insulating cups. The cups are made of ceramic or composite materials.
Salting the path of least resistance
"It puts an insulation between the high voltage carried by the conductors and what we call ground, which is the metal structure of the towers," he said. "The insulator cups have the job of confining the electricity."
He said the layer of surrounding air also provides insulation, removing any path for the electricity to go from the lines to the ground. That lets us move electricity around the province without shocking anyone en route.
When salt — or any other contamination — gets in that air layer it opens a new "path of least resistance" for the lazy electricity to head to the ground. "This is a situation that is undesirable," El-Hawary said.
Murray Douglas of EasternShoreMedia captured the dramatic results near Porters Lake on Jan. 4.
When that happens, the power cuts out. Usually it's short enough that if you time your blink right, you won't notice the lights flicker. But if it persists, the power is turned off for safety reasons.
"Nature works with us, because as soon as a contamination happens, you will find there is rain, there is wind, that will help in getting rid of that contamination," El-Hawary said.
The longer outages happen when nature doesn't help us. The circuit becomes contaminated, creating a dangerous situation that can damage equipment and hurt nearby animals and people.
Ice can build up on the conductors and do the same thing. El-Hawary said it happened in Newfoundland a few years ago during an ice storm, and in Quebec before that.
31,800 kilometres of power lines
Using sand on our roads instead of salt would help a bit, but would do nothing for coastal routes, where salty air is pervasive. That sea salt can affect lines 10 to 15 kilometres inland, he said.
Burying the power lines would also end the issue, but at a great cost.
"Even Saudi Arabia has power lines above ground," El-Hawary said.
Nova Scotia Power said the salt buildup can affect transformers, arrestors, insulators and wires. Given that the company has 1.5 million insulators, 500,000 power poles, and 31,800 kilometres of power lines, keeping them all salt-free can be difficult.
Florida sprays the equipment clean when a salt buildup occurs, but there's a reason Nova Scotians fly south in the winter: spraying here would just cover it in ice, leading to the same problem. Plus, they'd still have to turn off the power to spray the equipment.
No 'feasible' fix found
Spokesperson Tiffany Chase said they've tried different materials for the insulators, but both porcelain and polymer still ended up salty.
"We have looked to other utilities for best practices in terms of prevention but have not identified affordable, and quite frankly, feasible solutions to stop the issue from occurring here in Nova Scotia," Chase told CBC News.
For now, the company focuses on fixing it quickly when it does happen.
"We would like to assure customers that we are doing everything we can to minimize service disruptions, when it is safe and possible to do so, and that salt contamination is an isolated issue that tends to occur in winter during specific weather patterns and conditions," Chase said.
With files from Richard Woodbury