MADISON (WKOW) — American Transmission Company (ATC) identified the cause of a July fire and power outage in a downtown Madison substation.
ATC said a component inside the Blount Street substation’s transformer failed, “generating combustible gases and resulting in a fire,” said Jim Vespalec, ATC director of asset planning and engineering.
The company, with the help of an expert from the Electric Power Research Institute, reached its conclusion after a visual inspection and taking apart the transformer.
The component was designed to regulate voltage and had been inspected, according to the company, three times in the week leading up to the explosion. The last inspection was conducted two days before the July 19 fire.
ATC said the component had been scheduled to be replaced three days after the fire.
“Based on our experience and consultation with the manufacturer, we took prudent action in scheduling the outage,” Vespalec said of the company’s decision to wait until the Monday after the last inspection to replace the component.
The fire began shortly before 8 a.m. and a few minutes later triggered a second blaze at the East Campus substation. The two are linked via underground cables.
Both substations are owned by Madison Gas & Electric, but some of the equipment, including the failed component, is ATC’s responsibility.
American Transmission estimated approximately 18,000 gallons of insulating fluid were inside the transformer at the time of the fire to cool and insulate its electrical components. The Wisconsin Department of Natural Resources (DNR) directed ATC to properly dispose of the fluid and the water used to fight the fire.
The company said it collected “a significant portion” of the insulating fluid.
The DNR also instructed ATC to test the water in Madison’s storm sewers for PFAS, a type of chemicals used in the foam to contain the fire. Concerns over PFAS led to the closing of two east side water wells earlier this year.
Results from those tests showed slightly elevated levels of PFAS in groundwater. “When we look at those numbers, from our perspective, they’re not particularly high,” Amy Barrilleaux, a Madison Water Utility spokesperson said when the results first came to the city’s attention. “In most cases, they’re surprisingly low.”
“With high lake levels at the time of the fire, there is no reason to believe any water was discharged into the waterways,” ATC said. However, Madison Water Utility has said it expects some chemicals did make their way into nearby lakes. “It’s hard to contain it all,” Barrilleaux said.
The company said the DNR will continue to monitor and direct what, if any, further action may be necessary.
ATC said it installed a new concrete pad at the Blount Street substation on which now sits a new transformer. The company hopes the equipment will be fully operational later this month.