Which operational risk increases when an electric power distribution transformer operates continuously above its designed thermal rating?

💡 Explanation

When a transformer operates above its thermal rating, excessive heat generation causes the insulating materials to degrade via thermal decomposition, resulting in reduced dielectric strength and increasing the risk of insulation breakdown. Therefore dielectric breakdown results, rather than ferroresonance, harmonic distortion, or stray current corrosion which are caused by other disturbances.

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