Inhibited rape-seed oil as substitute for mineral oils

Former investigations with rape-seed oil of food quality proved favourable electric characteristics for using rape-seed oil as insulating material in electrical devices. Nevertheless ageing causes problems, if non-inhibited rape-seed oil is used. Regarding typical transformer life cycles of 30-50 years, improving ageing resistance of vegetable oil is a major issue. Inhibited rape-seed oil of high oxidation stability was developed in co-operation with a German oil mill. Stability was established by addition of antioxidants and complexing agents of little quantity. The stabilised oil is still classified as "in general not hazardous to water" as an equivalent to former water pollution class 0 according to German Federal Water Act (WHG). OECD degradation-test yielded to biological degradation rate larger than 80% within 28 days test period. Hence, stabilised rape-seed oil has superior environmental and health properties compared to mineral oils. Like for non-inhibited rape-seed oil, flash point of oil exceeds normative requirements by far. Nevertheless electrical properties remain favourable.