Managing Transformer Oil


Transformer Oil Sampling & Analysis is a key part of any Preventative Maintenance Program. It is strongly recommended that Transformer Oil Samples be drawn and analysed on an Annual / Bi-Annual basis – with a History of results to compare from year to year.


Transformer Oil Testing is a Proven Loss Prevention Technique – which is basically an Early Detection System, in order to identify maintenance priorities. The Transformer Oil is part of the Transformers Insulation System and is it therefore very important to periodically carry out associated oil analysis, in order to determine whether the Transformer is capable of performing its role in Industrial Environments.

Transformer oils are subject to electrical and mechanical stresses while a transformer is in operation. In addition there is contamination caused by chemical interactions with windings and other solid insulation, catalysed by high operating temperatures. As a result the original chemical properties of transformer oil changes gradually, rendering it ineffective for its intended purpose after many years. Therefore this oil has to be periodically analysed to ascertain its basic electrical properties, making sure it is suitable for further use, and ascertain the need for maintenance activities like Oil filtration. These tests can be divided into:

1. Di-Electric Strength (KV)1. PCB Analysis
2. Water Content (PPM)2. Dissipation Factor – Tan Delta
3. Acidity (mg KOH/g)3. Acidity (mg KOH/g) 3. Resistivity
4. Dissolved Gas Analysis (DGA – PPM) – See Photo 14. Sediments & Sludge
5. Furan analysis (PPM & DP) – See Photo 25. Interfacial Tension
6. Colour & Appearance6. Density & Flash Point

The Furan and DG Analysis have been specifically introduced for determining any abnormalities in the internal windings and paper insulation of the transformer. The Annual DG Analysis is a very important test for liquid insulation. Analysis of gases in the oil can indicate insulation overheating/overloading, liquid overheating, partial discharge (corona), or arcing in the transformer.


No single test alone will indicate the true condition of the liquid, so Regular Analysis should be performed.

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