A day after two transmission lines were tripped near Medicine Bow, causing tens of thousands of customers in eastern Wyoming and western South Dakota to lose power, electricity has been restored.
But questions remain about what caused the 500-kilovolt transmission lines in southern Wyoming to trip.
“The cause is still being determined,” said Lynn Kendall, spokesperson for Black Hills Energy.
Wes Ashton, vice president of Black Hills Energy South Dakota and Wyoming Utilities, told Cowboy State Daily that the outage happened on the regional grid, outside of Black Hills Energy’s footprint.
“We’re working to get questions addressed,” he said Friday afternoon.
Because of the scale of the outage, a full investigation will be conducted, he said.
An ‘Abnormal Event’
Ashton expressed appreciation for the patience of utility customers as line crews worked to restore power across the utility’s customer base of 77,000 in South Dakota, Wyoming and southeastern Montana.
“We worked diligently to safely restore power and make sure our community was safe,” he said.
Overall, the outage impacted nearly 100,000 customers of multiple utilities from west of Casper to east of Rapid City and from Sheridan to the northern edge of Cheyenne.
Other electric providers impacted included Montana-Dakota Utilities, Rocky Mountain Power and Basin Electric.
According to the Western Area Power Administration (WAPA), the outage “was initiated outside of WAPA’s transmission system in central Wyoming.”
The line trips resulted in an “abnormal voltage event” that affected some of WAPA’s transmission lines, causing further power outages across the region.
Fires In Sheridan County
A high-voltage power surge dropped sparks along a rural stretch of road from Arvada, Wyoming, to the Montana state line, blowing out numerous fuses.
“We had multiple fires as a result of power lines that were energizing,” said Sheridan County Emergency Management Coordinator Jesse Ludikhuize.
Seven fires ranging from half an acre to 50 acres resulted from the surge. All fires were quickly extinguished, with the help of ranchers and rural volunteer fire departments including Goose Valley and Big Horn.
No major issues were reported in Carbon County, said Wyoming Office of Homeland Security Director Russ Dalgarn.
In his 17 years as director, Dalgarn said he has never seen a power outage of this scale.
“I think the reason so many people were without power is because the breakers were tripping, as they should,” he said.
Generators Kicked In
Power went out at Memorial Hospital of Carbon County, but backup generators fired up immediately.
Generators likewise kicked on as intended at Weston County Health Services in Newcastle, according to Denice Pisciotti, assistant to the CEO.
While power was not out for a long time, its unpredictable fluctuations resulted in the radiology department shutting down for the afternoon.
“(We operate) very complex machines, so it’s really critical that our power stays consistent,” said Radiology Manager Keisha Brueggeman.
“We got lucky in patient care, because there were no trauma or strokes that came in, but we did have to reschedule some patients,” she said.
It took 90 minutes to restore all machines to full power Friday.
They Train For It
Jesse Ludikhuize with Sheridan County’s Emergency Management said the Wyoming Office of Homeland Security conducted drills related to a massive power event last year.
At the local level, emergency management personnel and first responders host seasonal meetings to discuss various scenarios like outages and how to distribute resources across the county if needed.
Emergency management was making plans to deliver gas to firetrucks and ambulances Thursday if needed because, Ludikhuize said, “Nobody could go to a gas station and get gas.”
But the power came back without first responders needing any additional resources.
Power Returns
Power was starting to be restored to Powder River Energy customers across northeast Wyoming by 4 p.m., the utility reports.
By 5 p.m., linemen were moving from substation to substation, bringing the power back.
“We tried to get humans into each substation before they reenergized them,” said Tim Velder of Powder River Energy’s marketing and communications team. “We were able to have people at every substation before power was restored. That was a good thing.”
A scheduled Pentatonix concert at The Monument in Rapid City was delayed by two hours because of the outage, and Rapid City’s downtown remained largely without power well into the evening, with police directing traffic at some major intersections.
By 8:30 p.m. Thursday, power had been restored to all of Black Hills Energy’s 77,000 customers.
An outage map at poweroutage.us showed 32 customers without power in Sheridan County early Friday afternoon. Otherwise, power appeared to have been restored to all affected counties.
Ashton said Thursday’s focus was all on restoration.
Now that the system has been restored and is stable, the focus turns to a broad-scale investigation of what exactly went wrong.
Electric systems are interwoven on a larger regional electric grid. This is by design to ensure a higher resiliency of power, Ashton said.
“It’s a very complex story,” he said. “Yesterday was something we will not only study, but we will learn from.”
