The best way to test the breakdown voltage of transformer oil is to use a transformer oil test kit. The main aim of such a test is to examine the insulating property of the oil in a dielectric transformer. If the breakdown voltage of the oil is on the lower side it means that it is of poor quality. First of all, in these cases you fill a vessel with the transformer oil – it is the vessel of the device that you are using to perform the test. It has a couple of test electrodes that are standard compliant. Under normal circumstances, they are at a distance of 2.5 mm from each other.
Location of the electrodes
In this process of the BDV test of transformer oil, the electrodes are in the midst of the dielectric oil. In usual cases, only a sample of oil is enough to serve the purpose in these cases. It starts with a test voltage that you apply to the electrodes. It is then increased at a continuous rate until the time it gets to the breakdown voltage. The slew rate here is constant and it is standard compliant as well. After the voltage reaches a certain point the breakdown happens and that too in an electric arc. This collapses the test voltage.
Switching off the test voltage
It is always better to use a proper transformer oil test kit in these cases. In the exact moment, the arc gets ignited you need to switch off the test voltage. It is the testing device that does this and it happens automatically as well. It is desirable that this switch off happens as fast as possible. The electric arc leads to carbonization and that needs to be mitigated so that there is no extra air pollution as such. The device that you use to measure the transformer oil basically measures the breakdown voltage and expresses it in terms of root mean square.
Repetition of the test sequence
Once the BDV test of transformer oil is completed the insulation oil gets stirred in an automatic manner. The test sequence also gets performed time and again after this. Depending on the standard there could be as many as 5 repetitions. After this entire process is completed a mean value is calculated for the various measurements and the breakdown voltage is expressed.
Why is this test important?
This test is important for the simple reason that you can check the quality of the transformer oil. When the transformer is being operated for a certain period of time the oil will become dirty, degraded, or both. This means that it is not able to work as well as it is supposed to or as it wanted to do earlier. This means that the transformer also is unable to cool or get insulated as well as it should be. If that happens there is a good chance that the transformer could face some major issues as well. This is why the test needs to be done at definite periods so that its quality could be properly tested.