Why is dielectric breakdown voltage of transformer oil essential for reliability?

High dielectric breakdown voltage provides margin against insulation failure under operational stresses, switching surges, and transient overvoltages. Oil is part of a composite insulation system with paper and solid barriers, and low BDV indicates contamination that can initiate partial discharge or arc paths. Reliable BDV reduces the probability of internal flashovers that can lead to catastrophic damage, fire, and outages. BDV also serves as a practical quality check for oil processing, filling, and sealing integrity, making it a key KPI for maintenance effectiveness and operational risk control.