ANSWER:

There are four main steps to follow to retrofill transformers with ester fluids, as follows:

1. Set up retrofilling plant

• Follow site procedures

• Ensure transformer is fully de-energised and grounded

• Perform site inspection and complete safety handover

2. Reduce mineral oil content as much as possible

• Connect pumps and hoses

• Ensure all pumps, lines and hoses are bonded and earthed

• Pump the mineral oil from the transformer to the waste container

• Rinse core and windings with heated ester fluid

• Allow time for the tank to fully drain

3. Fill again using new ester fluid

• User heated fluid

• Use dedicated hoses and pumps to prevent contamination

4. Test and nameplate

• Perform safety inspection and complete handover

• Take fluid sample to carry out appropriate testing

• Attached MIDEL nameplate as confirmation that the transformer has been retrofilled.

The video below goes through the process and benefits of retrofilling with Midel ester fluids.

MORE READING

For more detailed information on retrofilling with Midel ester fluids, visit our dedicated Retrofilling page, which has information on the reasons for retrofilling, case studies and supporting technical documents.

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?