The Benefits of FR3® Fluid in Transformers

‍Liquid-filled transformers depend on oil for their smooth operation. This transformer oil keeps the transformer cooled, insulated, and lubricated. Not all transformer oil is created equal, though. While mineral oil has powered the world since the 1900s, it’s not without its issues. Natural esters like FR3® fluid have quickly become the fluid of choice in oil-filled transformers.

What is FR3® fluid?

FR3® fluid is a natural ester made from seed oils—just like the vegetable oil in your kitchen. It is a safer, more sustainable alternative to the standard mineral oil found in many older transformers. FR3® fluid has been around since the 1990s and is the primary alternative insulating fluid to mineral oil in the United States.

FR3® fluid vs. Mineral Oil

For decades, the go-to fluid in oil-filled transformers was mineral oil. However, FR3® fluid offers many significant advantages over mineral oil. Here’s a rundown of why you should consider FR3® fluid for your liquid-filled transformer.

Benefits of FR3® fluid

Reduced Fire Risk

The flash point of mineral oil is 155°C. FR3® fluid, however, has a much higher flash point of 330°C. FR3® fluid is also classified as a “non-propagating” fluid, meaning it is self-extinguishing and won’t burn continually if it does catch fire. The upshot is that there is a far lower fire risk with FR3® fluid than with mineral oil. In fact, FR3® fluid is used in millions of transformers, and, to date, there have been zero reported pool fires in transformers filled with FR3® fluid. Even if a catastrophic failure occurred in an FR3-filled transformer, it is highly unlikely that a fire would start.

Besides reducing the risk of fire, FR3® fluid eliminates the significant costs associated with fire safety precautions. NEC standards permit FR3-filled transformers to be installed indoors without costly fire-suppression sprinkler systems. Additionally, they can be installed with a minimum wall clearance of only 3 feet, allowing for greater flexibility in installation locations.

Life Expectancy

FR3® filled transformers have a life expectancy 5 - 8 times greater than units with mineral oil. This is due to how FR3® handles moisture.

Moisture is the sworn enemy of paper insulation in transformers. It is a large factor in the breakdown of a transformer’s insulation. Moisture lives in two places inside a transformer, the paper and the oil. Most of this water resides in the paper. 

Under heavy loading and high temperatures, the paper releases water molecules. When loading and temperatures go down, the water absorbs back into the paper. Over time, this water can accelerate the paper’s aging. When the paper fails, the transformer is at the end of its life. So, getting rid of this water is key if you want a longer and happier transformer life.

This is where FR3® stands apart. For one, FR3® has a higher saturation point than mineral oil. Its ability to absorb and hold more moisture helps deal with water trapped in the paper. FR3® draws water molecules from the paper and into the oil. Then, through special chemical processes, the water is broken down and removed permanently. 

One way to see this in action is to look at oil samples in transformers with FR3®. You may see higher water content on the first few samples. But, later samples may indicate the water content has decreased. Why? Because the FR3® fluid has broken down some of those water molecules over time.  

Removing moisture from the paper does two big things. One, it extends the transformer’s lifespan. Two, it limits rapid aging that occurs in water-saturated paper under high temperatures. This allows the transformer to operate safely at higher temperatures.

These benefits are not for new transformers only. The life of the paper in older mineral oil-filled units may also be extended by retrofilling with FR3®.

Transformer Performance

In addition to extending the lifespan of the transformer’s insulation, transformers with FR3® fluid are also able to operate up to 20°C warmer than mineral oil-filled units. This significantly increases the transformer’s loading capability, up to a 20% increase in rated kVA.

Environmental Impact

Since it’s derived from seed oils, FR3® fluid is entirely biodegradable. It has over 99% biodegradation in just 28 days. FR3® fluid contains no petroleum, halogens, silicones, or sulfurs. Additionally, it is entirely non-toxic when it does biodegrade—it won’t pollute the soil or groundwater. This means that if your transformer springs a leak, you won’t incur high remediation costs for the spill.

Mineral oil, however, is hydrocarbon-based and non-biodegradable. Because it does not quickly bio-degrade in soil and water, mineral oil-filled transformers could require costly containment measures, not to mention the expensive cleanup work in the case of a spill.

Cost

Speaking of cost, FR3® fluid costs roughly twice as much as mineral oil. This may seem like a significant drawback, but the additional costs of using mineral oil can be even more significant. From additional safety measures necessary to prevent environmentally destructive oil spills to the higher fire risk and the attendant costs of fire suppression systems, mineral oil is not always worth the cheaper price tag.

Conclusion

Even though mineral oil was the go-to for over a century, transformers and the electrical grid are far better served by FR3® fluid. From safety to performance to life expectancy, FR3® fluid offers nothing but benefits. If you want to know more about FR3® fluid, fill out the form below.

And if you need to get FR3® fluid for your unit, check out our transformer parts page. We're here to get you what you need for your project.