Thermal Performance and Fire Safety
Regarding the characteristics for mineral oils and other dielectric liquids, the thermal properties of
vegetable oils appear as equivalent, or better.
Thanks to a better caloric transfer vs. slower circulation, it can be estimated that the thermal
conductivity and specific heat could compensate for the slightly too high pour point and
low-temperature viscosity.
The comparison between coefficients of volume expansion shows that the vegetable oil one is the
lowest. This characteristic means that the designed tanks of conventional transformers can be used
trouble free when filled with such liquids.
In addition, test data show that the vegetable oil and ester based fluid has the highest ignition
resistance. The flash point and fire point are above those of less-flammable dielectric fluids currently
available.
So, natural vegetable fluids appear as an interesting new non-flammable liquids, that could answer to
the banning of PCBs and other halogenated dielectrics fluids used in liquid-filled fire resistant
transformers.