Why is transformer oil dielectric strength critical for insulation performance?

Dielectric strength determines the oil’s ability to withstand electric stress without breakdown. Low dielectric strength increases risk of partial discharge, arcing, and insulation failure. Moisture, aging, and contaminants reduce dielectric strength rapidly. Maintaining high dielectric strength ensures insulation coordination, protects windings and paper insulation, and prevents internal faults. Regular testing and oil treatment are essential to preserve safe operating margins, especially at high voltages.