Q: What causes a transformer fire?

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A: When an internal fault takes place in an oil-filled transformer, a large volume of explosive gasses are created by a high voltage arc, vaporizing the oil. This fault creates pressures so rapidly that current PRV’s and sudden pressure relays cannot react in enough time before the pressures rupture the tank causing 100’s of gallons of oil to spew out.

The gases making contact with the oxygen in the atmosphere explode igniting the oil remaining in the tank, causing a secondary explosion which rains down flaming oil everywhere.