Naka Power has offered the most comprehensive account yet of the failure that caused some Yellowknifers to lose power for seven hours or more in early April.
The Saturday, April 5 outage was the city’s longest this century and one of Yellowknife’s most disruptive blackouts of all time.
In Yellowknife, two power companies are involved in keeping the lights on. The NWT Power Corporation generates electricity and Naka Power then distributes it.
We already knew the fault lay with a Naka Power breaker at its Niven Lake substation.
At a public hearing about power rates late last week, Naka Power executives provided more detail.
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Here’s Naka Power’s Jay Massie, quoted in a transcript of proceedings:
“It’s a key breaker where the electricity feed for the city comes into that substation from NTPC’s Jackfish site. There’s three main substations in Yellowknife; this is one of them. So where the power came in with that piece of equipment, well, it came to an end-of-life, electrically speaking. So it’s damaged completely beyond repair … it failed.
“That caused upstream protection in NTPC’s substation and on their grid to operate, so when the fault happened, it shuts power off. My understanding is that this was supplying nearly half the city’s power at the time. And when you lose that amount of load, especially on a hydro grid … the hydro has a tough time responding to that very quickly. So there is protection – [underfrequency protection], it’s called – and it’s really just to try and protect all electrical equipment from any more damage. And it shut off the rest of the system, is my understanding, from NTPC’s side.
“That piece of equipment was the root cause, our piece of equipment that failed. It’s working on being replaced here in the next day or two.
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“I can say from experience, in these large outages and when there’s two utilities working to coordinate to get the lights back on, it can be pretty hectic for the folks in the field to figure out exactly what the cause was at the beginning. So that takes some time, to figure out just what that exact cause was.”
Massie told the hearing the equipment is 13 to 15 years old and Naka Power “would expect it to last longer.” He said an investigation will take place.
Naka Power manager Vic Barr said the April 5 incident was “very rare,” adding that “the reliability of Yellowknife’s distribution system has historically been very strong.”
Barr said the company had been working to improve reliability by installing protection like “bird mitigations” designed to avoid outages caused by ravens.
Even so, on Monday this week, Barr told True North FM the city’s latest outage – a Sunday morning blackout that lasted a little over half an hour in some areas – appeared to be raven-related.
