Electrical properties of rape-seed oil

In order to verify possible application fields of rape-seed oil as insulating material, detailed investigations of dielectric properties - like dielectric dissipation factor tan δ, relative permittivity ε_r, specific DC resistance ρ - and breakdown strength under AC stress have been carried out. Relevant parameters, with respect to electrical and dielectric properties, are water content and oil temperature as well as field strength and frequency. As rape-seed oil is a suitable transformer oil substitute, obtained results are compared to conventional mineral oil based insulating fluid Shell Diala D. Results show, that properties of rape-seed oil are close to properties of mineral oil. Particularly 50 Hz breakdown voltage is as high as in mineral oil. Dielectric dissipation factor and specific DC resistance satisfy operation requirements. In transformers with solid-liquid insulation, higher permittivity of rape-seed oil in comparison with mineral oil would enable favourable field distribution in co-action with cellulose paper. At large, evidence could be provided, that rape-seed oil possesses suitable electrical properties for use in power supply equipment.