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Transformer replacements at Darlington Nuclear set to ensure reliable delivery of clean power

At OPG’s Darlington Nuclear Generating Station, first-of-a-kind work is underway to replace key transformers responsible for delivering the station’s clean power to Ontarians.

A look at new transformers installed at Darlington Nuclear's Unit 3 in July 2021.
A look at new transformers installed at Darlington Nuclear's Unit 3 in July 2021.

As part of the station’s ongoing refurbishment, this latest overhaul project aims to install new Main Output Transformers (MOT) and Unit Service Transformers (UST) at each of Darlington’s four units.

The MOT steps up the voltage of the electricity generated at Darlington so that it can be safely transmitted to the grid. Meanwhile, the UST steps down the voltage to help power auxiliary systems at each Darlington unit.

With more than 25 years of in-service time, Darlington’s transformers are approaching their end of life. The project to replace them is the first of its kind for the station and for OPG.

“These transformers are the final piece of the puzzle for the Darlington station,” said Teodora Tasic, a Technical Engineer with OPG’s Nuclear Projects division. “They ensure the electricity generated here can be transmitted throughout Ontario and to the station to support important auxiliary systems.”

This project and the overall four-unit Darlington Refurbishment will ensure the station can continue to provide clean, reliable electricity for the next 30-plus years to help power province-wide electrification and fight climate change.

So far, construction and partial commissioning of Unit 3’s transformers, which were manufactured by Hitachi Energy, have been completed on budget and on schedule. These transformers will be ready to support the unit, which is currently undergoing refurbishment, when it comes back online in 2024.

Meanwhile, the project team has completed designs for new transformers at all the remaining units, with the next replacement set for Unit 1, which is also currently undergoing refurbishment.