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Expert points to overheating transformer as likely cause of Madison substation fire

MADISON (WKOW) — MG&E, ATC and DNR crews have been on site at the Blount Street Substation since Friday’s explosion and fire and since the beginning they’ve pointed to an electrical failure as the cause.

On Tuesday, ATC confirmed to 27 News the transformer was the source of the failure.

To learn more, 27 News shared the details and video of the explosion with electrical and computer engineering professor, Daniel Ludois, from UW-Madison.

He said the transformer, which is where the fire appears to originate in the videos is full of mechanical parts meant to manage the voltage of the electricity flowing through the city system. It also comes with its own cooling and lubrication system which means it contains a significant amount of oil.

“In this situation, the transformer experienced something that caused it to overheat and the pressure to build inside of it, explode and then the oil inside of it caught fire,” Ludois said.

As for what caused the transformer to overheat, Ludois said that’s more difficult to pinpoint. He believes the malfunction likely happened in one of the parts meant to keep the transformer cool.

“Somewhere in the chain link there was something that caused that particular transformer to overheat, whether that’s a fan failing or a release valve not functioning,” he said.

According to Ludois, these types of fires and explosions are uncommon but happen across the country and around the world. In most cases, the cause is different.

Ludois said it could happen because of an animal getting caught in one of the transformer’s fans or a transformer could fail due to the degradation of their insulating oil.

At this point, ATC has not pinpointed any specific parts in its investigation. According to a news release sent out Monday, ATC performed an inspection on the Blount Street Substation just days before the fire.

“As part of those inspections, we identified one component within the substation that we felt required additional review,” the release said. “That component is part of our investigation. We do not want to draw any conclusions until we review all possibilities.”

ATC expects to complete its investigation by the end of the month.

Michelle Alfini

Reporter, WKOW

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