Which outcome occurs when a large, three-phase power transformer experiences a sudden, sustained increase in core temperature at a substation distribution system?

💡 Explanation

A sudden rise in core temperature increases the rate of thermal degradation of the transformer oil; this leads to increased dielectric oil breakdown, because overheating causes chemical changes lowering its insulation strength; therefore, insulation failure is more likely to trigger internal arcs, rather than the other alternatives at the listed temperatures.

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