ANSWER:

There are a range of MIDEL fluids to suit various climatic conditions. The performance of each fluid under cold climate conditions can be characterised by the pour point.

Transformer cold start procedures depend on the liquid type and temperature. Users can refer to IEEE C57.93 or IEEE C57.106 for guidance.

In line with other soy-based natural esters, the pour point of MIDEL eN 1215 is around -18°C, meaning that enhanced engineering controls may be needed for the coldest climate locations, e.g. heat tracing on conservator pipes.

This requirement reduces with rapeseed-based MIDEL eN 1204 which has a lower pour point of -31°C. For extremely cold climates users may wish to opt for synthetic ester-based MIDEL 7131 which has the lowest pour point. MIDEL 7131 is in operation in the coldest regions of the world, including Siberia.

MORE READING:

For more information on how Midel transformer fluids perform in cold weather, download the technical sheet: Cold start behaviour and dielectric performance.

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?