Extended Yellowknife power outage caused by breaker failure: Naka Power

A broken breaker at a power distribution substation caused Saturday's extended power outage in Yellowknife, Naka Power says.

Jay Massie, the utility company's vice president, told CBC News that the city-wide outage was caused by the failure of an "integral" piece of Naka Power's equipment, a "big breaker" at one of its three power distribution substations for Yellowknife.

"It just failed completely," Massie said.

The outage began around 3 p.m. MT. Some Yellowknifers got their electricity back around 5 p.m., but many were without power for much longer. The last Yellowknife customers had power restored around 10:30 p.m., leaving them without electricity for over seven hours, Massie said.

The outage also affected Behchokǫ̀, N.W.T., leaving residents there without power for about an hour Saturday afternoon.

Massie said the failure of the "integral" breaker, which was located at Naka Power's Niven Lake substation, was the "root cause" of both the Yellowknife and Behchokǫ̀ outages.

He added that Saturday's outage was unrelated to another extended outage in Yellowknife that occured several weeks ago.

Unanswered question about outage

The breaker's failure was "unexpected", Massie said, and Naka Power still doesn't know what caused it. He added that crews have not yet found any indication that anything was wrong with the breaker leading up to the outage.

"It's not typical that we see that piece of equipment fail as it did," he said. "It's about 15 years old. Still, we test and maintain them on a yearly basis."

Massie said it was also "unexpected" that the failure of this breaker would cause a city-wide outage at all — let alone an outage in Behchokǫ̀, a community more than a 100 kilometres northwest of Yellowknife that has a different power distributor.

Naka Power doesn't know yet why the broken breaker caused such a serious outage, but it and NTPC — the power distributor for Behchokǫ̀ — are investigating, he said.

CBC has requested an interview with NTPC about the cause of the Behchokǫ̀ outage.

Confusion around the unexpected severity of the power outage was part of the reason it took so long to fix, Massie said.

Technicians originally thought an issue with the power generation in Yellowknife caused the outage, he said, adding that NTPC would have had to fix that.

Naka technicians started repairs after 4:30 p.m., once they realized the company's own broken equipment caused the outage, he said.

Breaker still needs to be replaced

Massie said Naka was able to end the outage by rerouting Yellowknife's electrical grid, to bypass the Niven Lake substation altogether. But the part that broke still needs to be replaced.

The company hopes to replace it and get the substation back online by the end of this week, he said.

Until then, Massie said Yellowknife will be getting all of its power from Naka's two remaining functional substations. 

Massie said there shouldn't be any reliability or demand issues on the city's power grid as a result of this setup.

"The distribution system is designed for this," he said. "Fortunately, it's not -40 C. But even in that time, when there's a lot of load on the system, the system is designed to back itself up."