What is the most suitable insulation power-factor test voltage for a 4.16kV dry-type transformer winding?

In power-factor testing of transformer insulation, it's important to select a test voltage that is appropriate for the voltage class of the transformer being assessed. For a 4.16kV dry-type transformer winding, using a test voltage that is too low may not effectively reveal potential insulation issues, while a test voltage that is too high might stress the insulation beyond its safe operating limits.

A test voltage of 2kV strikes a suitable balance for a transformer rated at 4.16kV. It is sufficiently high to evaluate the insulation integrity and power factor under conditions that closely mimic operational stresses. This voltage helps identify issues like moisture ingress, insulation degradation, or contamination without risking damage to the insulation system.

Lower voltages such as 1kV might not provide an adequate assessment of the insulation state, as they can lead to inconclusive results where existing faults are not detectable. On the other hand, test voltages like 3kV or 4kV, while potentially revealing more, may introduce unnecessary stress to the transformer insulation, which could lead to premature failure or create defects during testing.

Thus, selecting 2kV is seen as the most suitable option to ensure that reliable and meaningful data about the insulation integrity of a 4