Equipment failure puts one of Yukon Energy's hydro units offline for winter

Yukon Energy says one of the hydro units at its Aishihik generating station will be offline until spring because of an equipment failure — but the company says it will still be able to meet the territory's power demands through the winter.

"Occasionally equipment fails. And we essentially have a contingency built into our system, so if a unit fails that we can still provide adequate energy to our ratepayers," said Paul Murchison, Yukon Energy's vice president of engineering.

Murchison said a part came off inside one of its three 15--megawatt generating units at Aishihik on Oct. 27 and was then knocked around inside the unit.   

"It's like a, you know, a metal piece rattling around in a spinning unit. It bounced around and did some damage," he said.

"We've had to shut it down and take it apart. And we'll have to essentially repair some components to that generator, then put it back together."

Murchison said it took about two weeks to determine the damage and realize the unit would have to be shut down for several months because "it wasn't going to be a really quick fix."

Now, the company is figuring out what parts need to be ordered and how long it might take to get them. 

"I can't say today whether the unit's going to be back in service in two months, or three or four months. It's that we just need to finish that root-cause analysis and find out exactly what parts we need to order," he said.

Pressure to the system in coming months

The Aishihik facility was built in 1975 and consists of three hydro units, two of which produce up to 15 megawatts, and a third that can produce seven megawatts. Yukon Energy says the facility provides about 25 per cent of the renewable energy available on the Yukon grid, including about 40 per cent of the territory's winter demand.

Having that unit offline will add pressure to Yukon's electricity system in the coming months, Murchison said, but the company will still have enough generating capacity even at times of peak demand.

In a press release, Yukon Energy said that it's also preparing for the potential relocation of some rented diesel generators to the Whitehorse generating site, if needed. Around 80 per cent of the territory's electricity demand is in the capital, the release said, and capacity might be "tight" if there were problems with the transmission line that connects the Aishihik facility to the southern grid. 

"We're not moving anything right now, but we are building a site that would allow us to move generators, and that just gives us a little bit more of a buffer from the contingency perspective, to be able to move those generators into Whitehorse if we need to," Murchison said.

Still, the company also said that it's preparing in case the grid in the south was strained and there weren't more diesel generators in Whitehorse. In that case, the company news release said, it would ask ATCO Yukon to use its diesel generators in rural communities, and ask the city and the territorial government to reduce power use in some of their larger buildings.

"We may also ask Yukoners to conserve electricity. Taking small steps like using a block heater timer and delaying the use of major appliances until later in the evening can help reduce strain on the power system," the release stated.