By CbS | 26-May-2021 | Some Tests and Their Values for the Transformer / Insulating Oil
Used Oil (Left) Filtered Oil (Right) Appearance The fresh transformer / insulating oil should be clear and free from the suspended or dissolved matter. The transformer oil should be visibly clear with no impurities in service. Any sludge deposit below 0.02% by mass can be overlooked.
Some Tests and Their Values for the Transformer / Insulating Oil
The oil should be free from free water, it present, then it is the sign of dissolved water reaching oil’s saturation point. The PPM or the moisture level in new oil should not be greater than 20 PPM, but can go upto 30 PPM in service if greater than this indicates that the inner paper insulation is also having moisture.
Breakdown Voltage
The BDV (Break Down Voltage) of the oil should be 30 kV or slightly more but can be reduced with in-service oil.
Acidity
The highest value for new oil is 0.03 mg KOH/gm but with usage, this value can go up to 0.05 mg KOH/gm.
