What Is the Transformer Oil Acidity (Neutralisation) Test?
Quick answer — The acidity (neutralisation) test measures the acid content of the oil in mg KOH/g, a direct indicator of oil aging. As the oil oxidises it forms acids, so a rising acidity indicates reduced oil quality, a risk of sludge and paper aging, and the need for oil treatment or replacement. It is a routine oil-condition test.
What does the transformer oil acidity test measure?
What it measures
The acid number (total acid number, TAN) is the weight of KOH needed to neutralise the acids in the oil, in mg KOH/g.
What it indicates
Acids form as the oil ages and oxidises; a rising acidity signals aging, a risk of sludge and varnish and accelerated paper aging.
When to act
High acidity usually means the oil should be regenerated or replaced, or the source (oxygen, moisture, high temperature) addressed.
References & standards
- IEC 62021 (acid number)
- IEC 60296 (oil)
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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