How is the breakdown voltage test of transformer oil performed?

The breakdown voltage test of transformer oil is performed by placing a sample of the oil in a test cell with two electrodes separated by a specified gap (usually 2.5 mm). The voltage is then gradually increased at a controlled rate until the oil breaks down and an arc forms between the electrodes. The voltage at which this occurs is recorded as the breakdown voltage. The test is usually repeated multiple times, and the average value is taken to determine the oil’s dielectric strength.