How is the BDV of transformer oil measured?

The BDV (Breakdown Voltage) of transformer oil is measured using a standardized test method, typically ASTM D1816 or IEC 60156. In this process, a sample of the oil is placed in a test cell with two electrodes. An AC voltage is gradually applied until the oil breaks down, causing a spark between the electrodes. The voltage at which this breakdown occurs is recorded as the BDV, indicating the oil’s insulating properties and its suitability for use in transformers.