Optimising transformer designs with natural esters
By DS Roesser, Cargill’s Industrial Specialities
Electricity+Control, May 2014 (pages 34-35)
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Cellulose paper, pressboard, and dielectric fluid typically comprise a transformer’s insulation system. A common failure mode of an electrical transformer is caused by the degradation of the solid insulating system (cellulose paper). Subsequently, the (temperature) operating limits of a transformer are constrained by the thermal capabilities of the insulating materials within each design. However, that changed with the validation of enhanced insulation system life and high temperature capability enabled by natural ester dielectric fluids.
Thermal ageing cannot be avoided or stopped, but it can be slowed. Natural esters, like Envirotemp FR3 dielectric fluid, perform very differently in the same scenario, thereby optimising transformer designs.
The comparative results of ageing studies are striking. As a mineral oil system ages and generates more water, it causes the system to age more quickly in a degenerative process. An FR3 fluid system is relatively ‘drier’ as the water it generates is consumed; the result is a much slower ageing process when operated at the same temperature as systems containing mineral oil. Evaluated using industry standard accelerated ageing test methods, an FR3 fluid system operating at conventional temperature limits lasts five to eight times longer than the equivalent mineral oil system.
- Cellulose paper, pressboard, and dielectric fluid are optimising transformer designs.
- Thermal ageing cannot be avoided or stopped, but it can be slowed.
- Compared to mineral oil, natural esters enable transformers to last longer.