American Transmission Co. plans to move a damaged transformer from a Downtown substation Wednesday as part of its efforts to discover what caused the device to explode six weeks ago.
ATC spokeswoman Anne Spaltholz said engineers visually inspected the 138-kilovolt transformer after it blew up around 7:40 a.m. on July 19, leaving thousands without power on the hottest day of the year.
The 130-ton transformer will be moved to Madison Gas & Electric’s former coal yard on Livingston Street, around the corner from the substation, which will result in some street closures on Wednesday.
Spaltholz said engineers will begin a “controlled teardown” — an exercise similar to a plane crash investigation — the week of Sept. 9 to determine what caused the fire. It’s not known how long that process will take.
“We hope that the condition of individual components will provide some answers,” Spatlholz said.
Spaltholz said ATC has been making repairs at the substation, including laying a concrete base for a replacement transformer, which costs about $1.5 million.
ATC, which maintains high-voltage lines for moving electricity over long distances, previously said it had identified a problem with the transformer and was planning a follow-up inspection the following week when it ignited.
According to a Madison Fire Department report released this week in response to a public records request from the Wisconsin State Journal, a lieutenant on the first engine to arrive said he met with an employee in a yellow hard hat who said crews “had been monitoring the transformer the last three days as the temperature of the transformer had been increasing.”
But, according to the report, when a fire investigator later asked about previous problems with the transformer, MGE’s safety manager said he couldn’t comment.
The fire department closed its investigation without identifying the specific cause, which it said will be up to utility engineers. According to the state Department of Justice, the State Fire Marshal did not investigate the explosion.
The Public Service Commission, which oversees utilities in Wisconsin, is awaiting the conclusion of ATC’s investigation to determine if there’s any need for regulatory action, PSC spokesman Matthew Sweeney said.
The North American Electric Reliability Council (NERC) is a nonprofit regulatory authority that sets and enforces reliability standards for the bulk power system, which broadly encompasses generators and transmission lines of 100-kilovolts or more.
NERC monitors compliance through self-reporting and audits. If the agency determines a violation is serious enough, it can impose penalties of up to $1 million per day, subject to approval from the Federal Energy Regulatory Commission.
Sonia Mendonca, director of enforcement and deputy general counsel, said NERC does not comment on open investigations or whether an investigation is underway in the ATC case.
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