How is the BDV test performed and what values indicate good oil condition?

The BDV (Breakdown Voltage) test is performed by applying a steadily increasing voltage to a sample of transformer oil until it breaks down, indicating electrical failure. The test uses a standardized apparatus with two electrodes submerged in the oil. A good oil condition is typically indicated by a BDV value above 30 kV for new oil, while values below 20 kV suggest contamination or degradation, necessitating further analysis or oil replacement.