Why is breakdown voltage critical for transformer oil quality?

Breakdown voltage is critical because it reflects the oil’s ability to resist electrical stress without forming an arc. Low BDV often signals moisture or particles that create conductive paths and raise the risk of partial discharge and internal faults. Since oil is both insulation and a heat transfer medium, poor dielectric quality can rapidly escalate into insulation damage, overheating, and catastrophic failure. BDV is a fast, practical health indicator.