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West Hit by Widespread, One-Hour Power Outage

November 9, 1989

Undated (AP) _ An unexplained power outage left cities in Wyoming and South Dakota temporarily without electricity Wednesday afternoon.

At least six cities lost power for almost an hour in the wake of a 5-minute ″power oscillation″ that affected Wyoming, Montana, Colorado and South Dakota.

Electricity was restored shortly before 5 p.m. MST, utility officials said.

Officials with power companies in all four states worked Wednesday evening to determine the cause of the fluctuation of current.

″We don’t know what caused it, we don’t know what started it,″ said Leslie Blythe, a spokeswoman for Pacific Power Co., headquartered in Portland, Ore. ″It seems to be stabilized right now.″

All power companies sharing a network of lines in the region experienced the oscillation, said Blythe, the company’s Wyoming spokeswoman.

″All of the utilities are tied into a grid system, all the lines are all tied together,″ she said. ″It may be happening in one area, but it is being seen all through the region.″

Power outages were reported shortly after 4 p.m. MST in Gillette and Cody, Wyo., and the South Dakota towns of Rapid City, Spearfish, Belle Fourche and Custer.

Most of the towns left without power are served by Black Hills Power and Light, based in Rapid City, S.D., and utility officials said their entire system was affected by the surge.

″We still don’t know what caused the power to go out, but it was a problem external to Black Hills Power and Light,″ said Joe Rovere, a spokesman for the utility. ″It knocked out all of our power in South Dakota, eastern Wyoming and eastern Montana.″

Jon Young, Gillette’s utilities director, blamed the outage on a shutdown of Pacific Power’s major transmission system east of Gillette.

″We’re just an island right here in the eastern portion of Wyoming,″ he said. Pacific Power is ″trying to patch everybody together.″

In Montana, a power surge tripped circuit breakers and knocked all coal- fired and hydropower plants of the Montana Power Co. off the power grid, spokesman Dean Conklin.

Conklin said power for most people in Montana was out only briefly as far as he knew. Electricity in the company’s headquarters in Butte, Mont., flickered out for a second or two, he said. A similar brief outage hit the capital city of Helena.

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