properties.
INVESTIGATIONS
In order to select the best raw material for electro-technical applications, we measured the main
properties of several seed oils and compared them with the IEC standards requirements for insulating
mineral oils [1] and synthetic organic esters [2]. As no specific international standards exist for
vegetable oils yet, the applicability of these two specifications was assumed.
Some candidate oils contain a high percentage of unsaturated fatty acids, resulting in lower viscosity
and better low-temperature properties. Others have a higher percentage of saturated acids, known to
improve oxidative stability. An optimal balance has to be selected between the two types of fatty acids
contents in seed oils.
Looking at dielectric formulations exclusively based on biodegradable and non-toxic vegetable
products, we have also tested some chemical derivatives of these seed oils. Mono-esters were prepared
from refined oils with different alcohols, such as methanol, iso-propanol etc. The reaction separates
the fatty acids associated into each triglycerid and creates three single esters. This could help to
improve the rheology of the oil.
The key parameters and the corresponding measuring methods which have been considered first are :
• Breakdown voltage
• Pour point
• Viscosity (at 40°C)