What is the tan delta test for transformer oil?

The tan delta test for transformer oil measures the dielectric dissipation factor, indicating the insulation quality of the oil. It assesses the oil’s ability to insulate and its degradation level by determining the phase angle between the voltage and current. A higher tan delta value suggests increased moisture or contamination, which can compromise transformer performance. Regular testing helps ensure the reliability and longevity of power transformers by monitoring oil condition.