Dielectric Ester Transformer Fluids: Safety and Environmental Impacts

Published under Technical Articles

Building and fire safety codes play a major role in distribution system design. The national electrical code states that transformer fluids must have a fire point not less than 300°C to be considered “Less-Flammable”. Transformers filled with fluids that have a fire point below that mark are unable to be installed in certain conditions. FR3 has a fire point of 360°C and a flash point of 316°C. This is much higher than other fluids and well above the “less-flammable” threshold. Not only does this allow for more installation options but can also effect insurance listing requirements due to lower risks. The property that FR3 is most commonly used for is its minimal environmental impact. In high environmentally sensitive areas, it is important to minimize any risk of contamination. When FR3 is spilled, thin layers polymerize and prevent the contamination of subsurface soils. It is formulated to minimize its environmental impacts and is completely recyclable, reusable, and biodegradable. If it is combusted, it produces carbon dioxide and water and is carbon neutral. All these properties make FR3 the best option on the market for transformer installations in environmentally sensitive areas where spills cannot be easily managed. Most transformers currently in service are filled with mineral oil. It is readily available and inexpensive, which makes it a good option for transformer fluid. Some fluids currently on the market are not miscible with mineral oil unfortunately. Silicone fluid will foam if it is mixed with mineral oil. This makes it impossible to retro-fill transformers that previously had mineral oil in them. FR3 and mineral oil do not have this effect. You can retro-fill transformers that were previously filled with mineral oil with FR3 without any negative impacts. The only thing to keep in mind is that no more than 7.5% by volume of the liquid can be mineral oil. If it is, it will reduce the fire point of the fluid to less than the required minimum of 300°C. FR3 is miscible with almost all other dielectric fluids other than silicone fluid. FR3 is a great option for transformers. It has excellent lubricity and can be used in equipment with moving parts such as regulators, sectionalizers, and rectifiers. The only downside is the initial cost when compared to mineral oil. It can vary anywhere from 2-5 times the amount that mineral oil costs. If the prolonged transformer insulation life and increased load capacity is considered though, it is a promising alternative to keep in mind when looking to source your next transformer. If you are interested in learning more or want to find a transformer that contains these fluids, don’t hesitate to contact us. Keep UTB in mind when sourcing your next transformer. _________________________________________________________________________________

Quinn Alleman

Utility Transformer Brokers


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