The company in charge of the transformer that burst into flames at an electrical station in Madison in July says it has found the cause of the blaze.
American Transmission Company (ATC) said in a release that a faulty voltage regulator sparked the fires, which left thousands without power on a brutally hot day.
The fires began the morning of July 19, when a transformer — a component that helps distribute electricity from place to place — burst into flames at the Madison Gas and Electric Blount Street substation in Madison. It sparked a second fire at a connected substation near University of Wisconsin-Madison’s Ogg Hall, causing evacuations.
ATC spokesperson Anne Spaltholz said it was an unlikely accident.
"Typically, when there's any kind of malfunction or failure on equipment in a transformer, the transformer automatically goes offline without a fire," Spaltholz said.
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That wasn’t the case for the Blount Street transformer. As previously reported, inspectors knew about the faulty voltage regulator before the fire, but the blaze started three days before they were scheduled to take the transformer offline.
"An incident like this is extremely rare, and we were very fortunate that no one was injured," said Spaltholz. "It was certainly inconvenient for the residents of Madison to be without power on a hot summer day."
Spaltholz added in an email that the transformers undergo a visual inspection every month that includes a check of the voltage regulator. The other transformer in ATC’s system of the same make and model has been inspected and deemed safe.
The company is working with the state's Department of Natural Resources to clean up any contaminants from the incident, including water that might contain PFAS, a harmful chemical in firefighting foam.
Editor's note: American Transmission Company is a sponsor of Wisconsin Public Radio.