The Northwest Territories Power Corporation has shared some information about the several power outages that impacted Yellowknife, Hay River, and Behchoko on Saturday, September 10 and Sunday, September 11.
Tree contact with a transmission line at Snare Hydro is believed to be responsible for the system-wide outage that occurred at approximately 5:31 p.m. on Saturday, September 10. High winds were reported in the area at the time. This outage lasted for one hour in Yellowknife and Dettah. Power restoration in Behchoko was delayed for an additional 22 minutes due to the failure of the diesel unit to start remotely as intended. An operator was sent to the community to manually start that unit.
The first outage on Sunday, September 11 began at 11:37 a.m. and lasted for approximately two hours. A tree was in full contact with the transmission line and was the initial cause of that outage. A line crew was dispatched to remove the tree as well as inspect other sections of the transmission line from Snare. High winds were again reported in the area. As part of NTPC’s vegetation management plan, danger tree removal on the Snare system is already scheduled for late September/early October.
The tree that fell on the transmission line this weekend would likely have been removed during that process.
As operators began the process of restoring power to the system using diesel, they ran into problems maintaining electrical stability. This resulted in a series of temporary outages in the early afternoon. Power was eventually restored at approximately 1:30 p.m.
A second full system outage occurred at 4:28 p.m. Electrical stability issues again made it difficult to restore power using diesel. Workers identified that a transformer at the Jackfish Generating Station was responsible for the stability issues, and it was taken offline. There were no further stability issues once the transformer was removed. A system operator was able to bring the system back online with a combination of hydro from Bluefish and diesel units at Jackfish by 6:10 p.m. Full restoration with hydro was completed at 6:47 p.m.
NTPC is conducting an inspection of the transformer to determine why it was not functioning properly on September 11. NTPC will make necessary repairs to the transformer before it is returned to service. NTPC is also looking into automation issues that prevented the remote startup of the diesel generator at Frank’s Channel.