ANSWER:

Power factor is the ratio of resistance current to capacitance current in an insulation system.

In new mineral oil transformers power factor is used to determine the level of insulation dryness. For operating transformers, changes in power factor can indicate increased levels of moisture or other contaminants in the insulation system. There are several variables that impact power factor measurements, even for new, essentially dry uncontaminated units, including:

• the ratio of solid to fluid insulation

• the type of dielectric fluid

• winding design

• temperature at time of measurement

Understanding MIDEL Power Factor

The dielectric dissipation factor of ester-based liquids is higher than that of mineral oil, due to the polar chemical structure of the ester. This in turn leads to higher power factor values for clean, dry insulation than would normally be seen with mineral oil.

Distribution transformers

Experience gained during the testing of transformers and published research has shown that the power factor of a new distribution transformer filled with MIDEL liquid will be around 50% higher than the same design with mineral oil.

Power transformers

In power transformers the liquid to solid insulation ratio will be higher and therefore the ester liquid will have more influence on the power factor value. It should be expected that the power factor will be approximately doubled after retrofill in a power transformer.

More questions on ester fluids?

This post is one of the 15 top questions we get asked on retrofilling transformers with ester fluids. Here is the full list of the frequently asked questions on ester fluid retrofilling:

1. Miscibility: Which transformer oils are compatible with Midel ester fluids for retrofilling?

2. Free-breathing: Can I use Midel fluids in breathing transformers?

3. Insulation Regeneration: Will Midel fluids heal existing problems in a transformer?

4. Fire Safety: Which dielectric fluids classifications are important to understanding fire safety?

5. Cold Weather: How do Midel fluids perform in the cold?

6. Moisture: What happens to the performance of Midel fluids when they absorb moisture?

7. Acid Levels: If Midel fluids have high acid levels, how do I recondition my fluid?

8. DGA: How can I use dissolved gas analysis on Midel fluids?

9. Power Factor: What is the Power Factor of Midel fluids?

10. Materials Compatibility: Are Midel fluids compatible with all transformer materials?

11. HV Applications: Can I use Midel fluids to retrofill transformers at high voltages?

12. Interfacial Tension: Is interfacial tension a meaningful property for Midel fluids?

13. Reusability: How are used Midel ester fluids processed and handled?

14. De-rating: Will there will be any derating of a transformer by changing it from mineral oil to a Midel ester fluid?

15. Retrofill Process: Are there extra requirements or steps when retrofilling transformers with Midel fluids?