Testing of Insulating Transformer Oil

At present, transformer oil is subjected to Breakdown Voltage (BDV) test for ensure its electrical strength. Other tests to confirm significant transformer features such as acidity, resistivity and etc., are not carried out before accepting bulk supply. Therefore, there is every possibility that manufacturers use inferior quality of oil. This can lead to poor insulation resistance among Low Voltage to Earth, High Voltage to Earth and High and Low Voltages and reduced cooling rate. Therefore, it could give rise to abnormal temperature increases even before loading the transformer to its rated capacity.

Therefore, it is significant to check whether the oil used is a new one or a reconditioned one or a reclaimed one before the transformer is installed. Water and water saturated oils both are heavier than clean and dry oil, or sink to the bottom of the container.

The subsequent tests are commonly conducted on the transformer oil:

1          Inspection of samples;

2          Acidity test;

3          Analysis of dissolved gases; and

4          Electric strength test.

We now briefly elaborate these tests.