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How often should transformer oil be changed?

B30 Transformer Oil 205L

Over time, the effectiveness of transformer oils will change, making them become less effective. As a result, equipment users carry out regular analysis at least twice a year to check the condition of the oil to assess whether it is still capable of performing its multiple roles. Unlike other types of lubricant, there is not a typical change interval for transformer oil. Instead, scheduled testing analyses its condition and changes are dictated by the results.

What factors can affect transformer oils change intervals?

When transformer oil requires changing can depend on many different factors. For example, operating conditions and work rates will affect how hard it must work and extreme temperatures and pressures can also impact the consistency and quality of the lubricant. How well a mechanical system is maintained call also have a considerable effect, with equipment that is correctly cared for more likely to experience a far longer lifespan in transformer oils in use. Electrical insulation is perhaps the most critical job of transformer oils. If water content within the transformer oil exceeds a specified amount, insulation performance can become greatly degraded.

Impacting oil quality

Excessive moisture is not the only issue that can lead to an oil change being required. Operating temperatures and exposure to air can both cause oxidation, lessening the effectiveness of the oils. The presence of metal particles can also be problematic leading the formation of carboxyl acid. The acid can cause the transformer’s cellulose to degrade but also lead to the formation of sediment that can impair transformer oil flow, stopping it from getting where its required and hampering heat dissipation.

The dielectric strength of a dedicated transformer oil refers to the greatest voltage that an oil can withstand without a breakthrough occurring. As electrical insulation is a vital function of transformer oils, any reduction of dielectric strength is critical and can be a sign that oil requires changing.

Changing transformer oil

If during bi-annual tests, transformer oil in use is discovered to be no longer able to perform its role, it can be changed with a fresh supply of dielectric fluid. Equipment user should always use a high-quality solution that is specifically suited to their transformer. Leading manufacturers like Petronas, Nynas and Millers Oils all produce built-for purpose transformer oils that are rigorously tested to ensure optimum performance and extended active service life.

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