Power Factor Testing

[ElectricalTestTech]

Does the pressure in a oil filled transformer matter when power factoring the transformer?

For some reason, I recall a topic at a NETA conference or Doble conference that mentioned something along the lines of "you should power factor under positive pressure and not a vacuum"...

This statement could be totally false and I cannot find any literature to back the statement up. Has anyone else heard anything along these lines?

[mask12900]

Any one knows how to perform Tan Delta Test on Dry Type Power Transformer of 2000 Kva and how to connect instrument with Transformer bushings please help me out .

Regards

[wooddy]

Does the pressure in a oil filled transformer matter when power factoring the transformer?

For some reason, I recall a topic at a NETA conference or Doble conference that mentioned something along the lines of "you should power factor under positive pressure and not a vacuum"...

This statement could be totally false and I cannot find any literature to back the statement up. Has anyone else heard anything along these lines?

cannot do hv power factor test(doble) under vacuum as you run a risk of flashover, pressure should not make a difference other than the moisture content of the dry air or nitrogen or sf6 in a breaker

[Kerry4407]

Does the pressure in a oil filled transformer matter when power factoring the transformer?

For some reason, I recall a topic at a NETA conference or Doble conference that mentioned something along the lines of "you should power factor under positive pressure and not a vacuum"...

This statement could be totally false and I cannot find any literature to back the statement up. Has anyone else heard anything along these lines?

I'm not aware of anything regarding the pressure of the transformer that would affect power factor results. Power factor is measuring the capacitance of the insulation and has little to do with the internal conditions beyond the bushings.

[Chipperk]

I'm not aware of anything regarding the pressure of the transformer that would affect power factor results. Power factor is measuring the capacitance of the insulation and has little to do with the internal conditions beyond the bushings.

Doble always recommends positive nitrogen pressure before powerfactoring xfmrs.

[Kalbi_Rob]

Doble always recommends positive nitrogen pressure before powerfactoring xfmrs.

As quoted from Megger "Application guide for power factor testing of power & distribution transformers" and attached to this post for reference:
"Never perform electrical tests of any kind on a unit under vacuum. Flashovers can occur at voltages as low as 250 volts."

As quoted from "Transformers: Basics, Maintenance, and Diagnostics"
"Transformers must not be sampled if there is a negative pressure(vacuum) at the sample valve. If there is a vacuum at the bottom, air will be pulled in when the sample valve is opened. Wait until the pressure gauge reads positive before sampling. Pulling in a volume of air could be disastrous if the transformer is energized."

Transformers_AG_en_V01.PDF