A large power outage swept across wide areas of Wyoming and western South Dakota on Thursday, cutting electricity to more than 94,000 customers after two major transmission lines failed near Medicine Bow.
According to the Western Area Power Administration, the two 500-kilovolt lines tripped unexpectedly, causing a sharp voltage drop that moved quickly through the grid. Stephen Collier, a public affairs specialist with the agency, said the disturbance set off additional line failures and resulted in rolling outages through multiple communities.
Several Wyoming cities — including Sheridan, Buffalo, Gillette, Newcastle, Glenrock, and Casper — experienced partial or full outages. With temperatures falling in the early evening, Sheridan County officials opened the fairgrounds exhibit hall to give residents without heat a place to stay warm.
As utilities were working to restore service, a separate issue was reported at the Dave Johnston coal plant near Glenrock, where a fire broke out on Thursday. Wyoming Department of Homeland Security Director Lynn Budd said the fire started after the grid problems had already begun. Investigators have not determined whether the plant fire and the transmission-line failure are connected.
Repair crews continued assessment and restoration efforts through the night. Officials said more information will be released once engineers complete their review of what caused the transmission lines to fail and whether additional grid protections will be needed to prevent similar incidents.
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