- dielectric strength;
- loss tangent;
- moisture content;
- gas content; and
- the presence of mechanical impurities.
Transformer oil is an petroleum product, used to insolate the active parts of transformers under voltage as well as cool and transfer heat during operation. The performance characteristics of this oil product depend on its chemical composition that is determined from the raw material and methods uesed in its purification. The commissioning of new electric power transformers requires only fresh oil that has not been previously in service. Each batch of the product intended for transformer refilling should be certified by the supplier. But, even fresh new oil delivered to the power facilities should be tested and, if necessary, cleaned of mechanical impurities, moisture and gases before being placed into the transformer. Performance characteristics of transformer oil are evaluated by the following indicators: