We get lots of questions on Ester Fluids…

Especially when it comes to retrofilling transformers. That’s why we’ve put this guide together on the top 15 questions (and answers) – to help organisations better understand the challenges and possibilities of retrofilling with ester and to assist them to make investment decisions with greater certainty.

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Reasons for Retrofilling Transformers

The motivations for power and distribution transformer retrofilling are numerous. They range from addressing an urgent need on a single asset, to rolling out a network-wide program with clear financial returns.

Each transformer has unique operational factors that influence the situation such as load, asset design, age, location, and environment.

#1 Reason: reducing risk with minimal cost

Risk is the most common reason for retrofilling mineral oil filled transformers with an FM Global approved ester fluid. Synthetic and natural esters like those from MIDEL can deliver significantly reduced risk with minimal CAPEX and OPEX.

Often at the top of the risk list is a reduced risk of collateral damage. This in turn can lead to other cost savings such as enabling fire mitigation equipment to be removed from service, eliminating maintenance, avoiding CAPEX on costly site works such as fire walls or transformer relocation.

When retrofilling mineral oil filled transformers with a natural ester or synthetic ester fluid there are additional financial incentives that support positive ROI.

This is due to the unique capabilities of ester fluids and their performance in transformers, resulting in cost savings without sacrificing reliability.

Many transformer owners can financially justify ester fluid retrofills based on just one of these factors. When multiple factors are evaluated together, they create a very compelling business case for retrofilling with ester fluids.

Here are the top 15 questions on retrofilling transformers with MIDEL fluids.

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?

A BETTER UNDERSTANDING OF MIDEL FLUID CHOICES FOR TRANSFORMERS

Which MIDEL?

The MIDEL family of transformer fluids comprises MIDEL eN 1215, MIDEL eN 1204 and MIDEL 7131. The “eN” prefix denotes natural esters, which are formulated using renewable base oils from different seed crops, whilst MIDEL 7131 is a synthetic ester fluid. All MIDEL fluids are fully/readily biodegradable. MIDEL eN 1215 is not sold in Australia.

Natural Ester Fluid

MIDEL eN 1204 is formulated from rapeseed/canola oil and is a cost-effective general-purpose fluid. Like all natural esters, it is ideally suited to non-free-breathing distribution and power transformers. This rapeseed/canola ester is suitable for use in all climates and has superior oxidation characteristics compared to soya ester fluids.

MIDEL natural esters meet the IEC 62770 standard.

Synthetic Ester Fluid

MIDEL 7131 is specifically formulated to be a fire safe, high performance fluid providing all the benefits of ester technology in an extremely robust formulation. It is the fluid of choice when the performance demands on the transformer are higher, especially if located in a cold climate (it has a pour point of -56°C) or when there is a risk of contact with air.

In addition to being suitable and widely used for distribution and power transformers, MIDEL 7131 is also ideal for high temperature, breathing type equipment. It has a long track record in demanding applications such as wind turbines and rolling stock and is proven up to 433kV. MIDEL 7131 meets the IEC 61099 standard.

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