Compatibility of polymer materials with natural-based insulation oils

Natural oils with their price and environment-friendly behaviour are more used these days like insulation fluids in transformers. There are often based on eg. rapeseed, soy, sunflower etc. oils. Compatibility between new materials used in transformers needs to be further discussed. Few papers already describe the behaviour of insulating papers and materials like gaskets, varnishes or core steel with soy or corn oil. This paper describes the compatibility of cable ties and rubber-based gasket and part of transformer bushing. These materials were placed into insulation oils, in our case rapeseed oil-based and for comparison to mineral oil Nynas Lyra, and thermally aged in the oven for 2000 hours at 120 °C and 1000 hours at 140 °C. All polymers and oils were analysed before and after ageing. Properties as weight and dimensions change, hardness by Shore and permittivity, resistivity, dissipation factor, the viscosity of oils are discussed.