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Pepco defends Wheaton substation transformer replacement after questioning on alternatives and testing
Summary
Pepco witness Jacqueline Young said the Wheaton substation transformer was replaced after dissolved‑gas analysis and repeated test results indicated gassing and other issues; the company told the Commission the transformer was 55 years old, exceeding typical useful life and raising safety and environmental concerns.
Pepco told the Public Service Commission that it replaced a Wheaton substation transformer after inspections and testing identified "gassing" and other condition issues the company said made replacement the prudent option.
Pepco witness Jacqueline Young testified that the Wheaton transformer exhibited leaking bushings and oil pumps, tapped dissolved gas analysis results showing progressive "gassing," and LTC (load tap changer) concerns. She said the transformer had reached 55 years of age — beyond the utility’s average replacement interval — and that those factors, combined with parts obsolescence and environmental considerations, supported replacement.
Young described remedial alternatives the company considered. One option was a full gasket replacement for the LTC and main tank that the company estimated at a lower near‑term cost but which would have required ongoing LTC inspection costs and, Young said, would not have addressed the transformer’s repeated gassing and the risk of catastrophic failure. "It would have addressed the issue we were dealing with at that moment, but it would not have addressed the the broader issues," she told the panel.
Stakeholders pressed cost‑benefit questions during cross‑examination. Counsel calculated a high‑level comparison of gasket replacement costs versus full replacement and questioned payback; Young said that gasket replacement would not have addressed gassing and other safety risks and that parts obsolescence and environmental cleanup risks made full replacement the better long‑term option.
Why it matters: Substation transformer replacements are capital projects typically included in rate base after in‑service accounting. Intervenors and staff probed whether less‑costly stopgap repairs would have been sufficient and whether the utility documented alternatives and test results supporting replacement. Pepco presented testing, age, maintenance history and industry practice to justify the replacement.
What’s next: The Commission will review how the project was justified and whether replacement costs should be included in rate recovery as part of the reconciliation and prudency review process.
