An unfortunate set of circumstances resulted in an outage yesterday in Mayo, Keno, Elsa, Stewart Crossing, and Dawson City.
Power went out on the Mayo-Dawson line at 3:43 p.m. as a result of what we believe was a lightning strike. Power was restored to the town of Dawson seven minutes later (six minutes in one section of town and seven minutes in the other) using the Dawson back-up diesels. However power didn’t come back on in the Hunker Creek industrial area until 7:45 p.m. A problem on what is known as the ‘express feeder’ that serves Hunker Creek prevented us from re-energizing that section of line. While that feeder is now working fine, we will be sending a crew there this week to investigate the problem.
In Mayo, Keno and Elsa power also took considerably longer to be restored. Normally in a Mayo outage we would use our back-up diesels in the community. For whatever reason, the diesels did not work last night. We would have fed Mayo using Dawson diesel, but the issue on the Hunker Creek portion of the line prevented us from doing that. Power was restored to Mayo at 7:42 last night and to Elsa and Keno, including the Alexco mine, at 9:20 p.m.
We have just recently energized the Carmacks-Stewart line and have been feeding Mayo and Dawson with hydro from the Whitehorse-Aishihik-Faro grid for the last several days. However we are still fine tuning the protection equipment at our Stewart Crossing substation. During this outage, the protections did not work as we expected them to and so we had to send someone to Stewart Crossing to manually close the breaker, allowing us to again feed Mayo, Elsa, Keno and Stewart Crossing with hydro power from Whitehorse.
This morning, all our customers are back on hydro power from our Whitehorse and Aishihik plants.
Today crews will be investigating the cause of the Mayo diesel problem, and then the necessary repairs will be made. The protections at the Stewart Crossing substation will be adjusted so that in another outage on the Mayo-Dawson line, hydro power should continue to be delivered from the southern portion of the Yukon grid. We are also sending another back-up diesel to Mayo this week.
According to the weather forecast we could see more lightning activity in the Mayo/Dawson area today. We are watching closely and are doing everything we can to prepare for another potential outage. We sincerely apologize to those who were affected by the power outage.
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