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 have quickly become the fluid of choice in oil-filled transformers.
What is FR3?
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 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 for your liquid-filled transformer.
Benefits of FR3 Fluid
Reduced Fire Risk
The flash point of mineral oil is 155°C. FR3, however, has a much higher flash point of 330°C. FR3 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 than with mineral oil. In fact, FR3 is used in millions of transformers, and, to date, there have been zero reported pool fires in transformers filled with FR3. 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 a catastrophic fire, using FR3 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.
FR3 fluid has a higher saturation point than mineral oil. Why does this matter? Transformer fluid can build up moisture during normal operation. FR3 draws this moisture out of the paper insulation and absorbs it, allowing the insulation to operate at a higher temperature and extending the transformer’s life expectancy. This makes FR3-filled transformers much more immune to dielectric failure and decreases transformer capacity due to moisture. Mineral oil-filled transformers cannot retain this moisture: as the temperature of the transformer increases, the moisture travels from the paper insulation to the fluid. Once the temperature decreases, all that moisture will return to the paper.
Because of its higher saturation point, FR3 can also slow the aging process of insulation paper, increasing the lifespan of the insulation system by as much as 5–8 times.
In addition to extending the lifespan of the transformer’s insulation, FR3-filled transformers 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.
Since it’s derived from seed oils, FR3 is entirely biodegradable. It has over 99% biodegradation in just 28 days. FR3 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.
Speaking of cost, FR3 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.
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 offers nothing but benefits. If you’re looking for an oil-filled transformer and want to know more about FR3 and how to buy the right transformer, fill out the form below.