At 9:07 a.m. and again at 9:09 a.m. on Wednesday January 13, Lethbridge Electric Utility experienced back to back transmission circuit outages.
This removed both provincial grid connections at 1 of its 6 supply substations, affecting about 25% (30Mw) of the city, primarily the downtown core.
Restoration of these facilities required some time for Transmission Lines and Substation Staff to perform technical and public safety inspections along the power corridors covering the entire length of the city. (approx. 40 km.)
In addition, Coordination Centre Operators and Distribution Line Crews managed multiple outages and downed wires within the city caused by fallen trees.
The follow-up investigation has verified that equipment operated correctly, however due to the extreme gusting winds of +125km/hr its suspected to have caused the power lines to slap together causing power flow swings.
The grid is designed across Canada to always be able to survive the loss of a single circuit, however this was an extremely rare event impacting two independent key assets, almost simultaneously.