In a nuclear plant, the transformer system performs the same electrical role as in other thermal plants: GSUs step up generator output to transmission voltage, station service transformers supply turbine-island and balance-of-plant loads, and reserve transformers ensure black-start capability. Reliability requirements are stricter due to safety-critical infrastructure, so monitoring, redundancy, and seismic-rated installation standards are common.

In addition to voltage conversion and power distribution, transformers in nuclear power plants are essential components that directly contribute to the safe and reliable operation of the entire facility. The transformer insulation system, especially insulating oil, shall maintain stable dielectric properties over many years of operation, because any degradation can affect equipment availability and increase maintenance requirements.
For this reason, condition-based maintenance plays an important role in nuclear facilities. Routine monitoring of oil quality, removal of moisture and dissolved gases, and timely purification help reduce the risk of insulation aging and unexpected failures. The same principle applies to other oil-filled equipment in a nuclear power plant, such as hydraulic systems, where clean and stable process fluid is essential for reliable operation.
For those interested in oil maintenance practices used in nuclear power applications, I would also recommend reading this article: https://globecore.com/oil-processing/nuclear-plant-hydraulic-oil-purification/.

Exactly — in addition to stepping voltages and distributing power, transformers in nuclear plants are safety‑critical assets whose life and availability hinge on maintaining the insulation system and oil dielectric properties. Routine oil testing for breakdown voltage (BDV), water content, dissolved gases (DGA), acidity and particle contamination, combined with online condition monitoring, lets you move to condition‑based maintenance instead of calendar‑based servicing. Active moisture control through drying (hot oil flushing, heating and vacuum cycles where the tank design allows), periodic oil purification and degassing, and prompt removal of byproducts that accelerate aging will reduce insulation degradation and lower the risk of unexpected outages. The same oil‑quality discipline applies to other oil‑filled systems in the plant, such as hydraulic circuits, where clean, dry fluid preserves actuator reliability and control‑system integrity.

For practical implementation I’d recommend pairing continuous online monitoring with targeted oil treatment and dry‑out equipment: an online monitor that tracks key transformer parameters and supports proactive alarms, combined with an online dry‑out unit for moisture removal and a vacuum/evacuation unit for tank dehydration and oil degassing. A typical maintenance workflow would use continuous monitoring to trigger laboratory and on‑site tests, then perform hot‑oil flushing and vacuum drying cycles or filtration/degassing and remediation using mobile CMM‑class equipment as needed; if a tank cannot tolerate full vacuum, use hot‑oil spray and incremental drying or consider mechanical reinforcement before evacuation. If you want, I can draft a short equipment shortlist and a suggested maintenance schedule tailored to a typical nuclear‑plant generator step‑up transformer bank.