Dielectric Ester Transformer Fluids: Extending the Life of Insulation
Insulation deterioration is a leading cause of transformer failures. Over its lifetime, it will degrade when subject to high temperatures. The insulation paper is commonly made of cellulose. A byproduct of cellulose degradation is a higher water content in the oil. There is some evidence showing that the water that is present in the cellulose will auto-accelerate the aging in oil. If the water is able to be wicked from the cellulose, it will slow the aging.
The acceptable saturation of water in FR3 when compared mineral oil is close to fifty times higher. Due to this, it is encouraged to store FR3 under a nitrogen blanket and avoid any unnecessary exposure to humidity in the atmosphere. However this means FR3 is able to wick away more moisture from degrading insulation paper, which in turn will decelerate the aging process. It is claimed that it can extend the insulation life by 5-8 times the amount that is normal with mineral oil.
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