What does the BDV test of transformer oil measure?

The BDV (Breakdown Voltage) test of transformer oil measures the oil’s dielectric strength, which is its ability to withstand electrical stress without breaking down. During the test, a gradually increasing voltage is applied to the oil sample until it breaks down, or a spark occurs. A higher BDV value indicates that the oil has good insulating properties and is capable of effectively insulating the transformer’s internal components.