Thousands of people throughout Steele County were without power for a few hours Tuesday evening following a failure professionals are calling “catastrophic” at a local substation.
The preliminary investigation has revealed a Steele Waseca Cooperative Electric transformer located at the West Owatonna Substation experienced a failure that eventually led to a de-energized transmission bus – the system that transports the power throughout the substation. SWCE Operations Manager Dan Meier said that it can be hard to decipher the exact cause of a transformer failure because of the extremely rare occasion that it happens.
“These events are an anomaly, transformers don’t just fail,” Meier said. “I believe the last time we had a transformer it was actually before my time here, so it was probably 25 or more years ago. It just doesn’t happen very often, which is fortunate, because when it does happen it is usually catastrophic like this.”
Though Meier said the extreme heat southern Minnesota has been experiencing throughout the last week was not the cause for the failure, it did not help the situation. According to Meier, there is a protection device that is put in place to protect a “cascading effect” of other transformers down the line being knocked out. Because of how hot and windy it was on Tuesday, however, Meier said that when oil misted out of the transformer, it caught on fire, causing an arch flash to go over the protection device and cause an outage upstream from the SWCE device.
“Our protection device did open and operate correctly, but the arching over that device led to another part of the substation being affected,” Meier said.
Because there are a number of utilities that own equipment within that specific substation, more than just SWCE customers were impacted. Roughly 7,000 customers with Owatonna Public Utilities lost power in Owatonna at the same time as SWCE’s 600 customers in the Medford area and 300 customers south of the substation, including those residing in Hope.
Representatives from SWCE and OPU said it is possible that Xcel Energy customers also experienced a power outage, though it is unknown at this time. Representatives from Xcel did not return calls for comment prior to press deadline.
The outage happened at roughly 5:30 p.m. Tuesday and most customers with both companies had power back within two hours. Meier said considering the extent of the failure that this response time is much better than should be expected.
“Because we do have redundancy built in to our system we had to roll linemen out, isolate the transformer, go to switching points on the system and feed it from another substation,” Meier said.
Moving forward Meier said they are unaware at this time if the transformer that failed will be able to function again, however the chances are not good. At this time, SWCE crews are busy cleaning the bus work and insulators so the substation can get back up and running, to which Meier said they are hopefully will happen by the end of the day Friday. Meier said they are also fortunate to have another transformer on site to replace the roughly $500,000 piece of equipment that failed Tuesday.
While the heat was not the direct cause of this particular power outage, Meier said there are situations where the heat can put a lot of stress on transformers.
“They perform better when it’s cool out – that’s no doubt,” Meier said. “You will see an uptick of power outages through the summer months, but mainly those will be due to storms – storms cause more outages than anything else. Lighting is not our friend when it comes to overhead power lines.”
With that said, SWCE and OPU have both been promoting cutting back on energy usage during “peak” hours to help prevent potential hardship on the equipment as well as help reduce community energy costs. Because both companies base their costs to their residents and businesses on the cost of doing business, energy costs for everyone go up drastically during extreme weather.
“Realistically we can handle it, but we just ask for everyone’s help,” Meier said, noting that utility infrastructure is specifically built to withstand both extreme heat and extreme cold. “It’s easier on the system to pull back a bit on usage.”
Some ways Meier said people can help is not using a hair dryer in the morning, starting laundry or dishwashers later in the night, and forgo the electric stove for the grill outside.
According to the National Weather Service, the Twin Cities metro and surrounding area has broken its record for consecutive days above 90 degrees this early in the season, which was previously six days. As of Thursday, it had been eight consecutive days.