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A transformer service lifetime is long and can be extended provided the transformer is adequately maintained.

Preventive maintenance in the factory of a transformer reduces the stress of aging, re-establishes short circuit strengths and improves dielectric strength. A well maintained transformer reduces operating cost and improves reliability.

Rehabilitation aims to restore key components of the transformer to a state as close to “as new” as possible by performing refurbishment and replacement actions without replacing major components such as the windings or core. To maximize the assets technical life, this refurbishment or overhaul can be an intermediate action when no failure has occurred yet but the ageing of the unit has reached a stage where the continued reliability of the transformer is unacceptable.

Scope of work

Upon receipt of the transformer in the factory, a visual inspection and electrical control will be performed to identify which rehabilitation actions will be taken, as well as to provide a delivery date. Pending the root cause and agreed actions taken, the active part will be untanked and inspected.

Following upgrade/service of noble parts, accessories and other auxiliary equipment, the active part is dried and replaced in the tank, which is refilled with oil and high-voltage test performed. After the factory acceptance test the newly revitalized transformer is ready to be delivered back to its owner.

If requested, Hitachi Energy can of course cater for the transport of the unit back and forth from the site.

The rehabilitation would not replace the windings or the core, but rather rejuvenate the transformer performing refurbishment on eg, coolers, radiators, breathers, pumps and valves, provide services such as re-gasketing, inspection and re-clamping of connections, oil filtration, revision of tap changer, or clean, re-tighten and dry the active part. All is concluded by performing the appropriate tests.

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Transformer service

Aging assets, rising energy demand, and the critical need to avoid unplanned outages are challenging worldwide utilities and industrials. The service portfolio of Hitachi Energy allows utilities and industrials to maximize the return on transformer assets by ensuring high reliability, reducing life cycle costs, and ensuring optimized performance while lowering environmental impact.
Hitachi Energy Power Transformers


Hitachi Energy offers distribution and power transformers, Dry-type and EconiQ™ Transformers as well as services, for industrial and commercial applications.
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