An update on the use of bio-based and sustainable liquids

The number of different insulating liquid types has increased in recent years and engineers must identify the trade-offs in utilizing different insulating liquids. Traditional naphthenic mineral insulating oils offer their long track record and well characterized electrical behavior, but they are not readily biodegradable. When fire safety aspects are key in the application; natural and synthetic esters are favored, but both require dielectric adaptation to transformer designs in the majority of cases. Both ester types are readily biodegradable but synthetic esters have a non-bio-based component whereas natural esters have lower oxidation stability. Bio-based hydrocarbon liquids do not have the high fire point of esters, but they are biodegradable, fully bio-based and have typically very low viscosities (providing an advantage in heat transfer). In other respects, they are fairly similar to classical mineral insulating oils. In this paper, the bio-based hydrocarbon’s properties are summarized and a case study, particularly focused on potential thermal performance of a transformer are presented.