Protect the paper, improve overall grid reliability
The number one factor that has the greatest impact on the life of a transformer is the insulation paper. Natural ester fluid is proven to protect the insulation paper 5-8 times longer than mineral oil. That extends asset life, reduces total cost of ownership and improves grid reliability.
Inside the transformer
Paper produces water as a by-product of thermal aging which acts as a catalyst for continued degradation. While thermal aging cannot be avoided, it can certainly be slowed down. How can you do that with a dielectric fluid?
The answer lies in natural ester fluid’s unique chemistry. Because mineral oil is hydrophobic, most water stays in the paper. However, natural ester transformer oil is comparatively hydrophilic, so water is absorbed by the fluid or wicked away from the insulation paper. At room temperature, natural ester has 10 times the water saturation level as mineral oil (it can dissolve over 1000 mg/kg of water before becoming saturated compared to 60 mg/kg for mineral oil at 20°C.)
Numerous published aging and electrical verification studies of cellulose and natural ester fluid provide surprising observations compared to the same studies in mineral oil. Cellulose was observed to last from five to eight times longer in natural ester oil than in petroleum-based mineral oil, confirmed by multiple studies.
Higher temperature capability with natural ester transformer oil further protects insulation system
Research has confirmed that the cellulose insulation is more protected from thermal degradation in natural ester oils because the fluid has 20 degrees more margin of thermal ability than mineral oil.
Thermally upgraded cellulose insulation in natural ester fluid has a transformer hot spot capability of 130°C compared to 110°C for the same cellulose in mineral oil. Within a transformer when the insulating paper ages, water molecules are released from the insulation which accelerate further degradation of the cellulose. However, with natural ester fluid, a hydrolysis reaction occurs whereby a molecule of water is converted to a non-reactive, long chain, free fatty acid thus absorbing the water molecule into the carbonyl structure of the natural ester. These fatty acids have no impact on the performance of the fluid or transformer. Also, they are non-corrosive as compared to acids generated with mineral oil.
Natural ester oil is self drying
With a natural ester-filled transformer, the water volume (ppm) allowed before reaching saturation and acid counts will be higher. That’s not a bad thing – that’s normal for natural ester fluid compared to a mineral oil transformer. By being able to absorb the extra water produced as part of the thermal aging process and having a higher water saturation point, natural esters protect the insulation paper (essentially ‘self drying’) thus extending the asset life and helping improve the grid reliability. Natural ester fluid can extend the insulation life of new transformers or the residual insulation life in a retrofilled transformer.
Improving the grid
Contact our dielectric fluids team to help you incorporate these cost-saving, performance-enhancing solutions into your grid.