New synthetic ester fluid for the insulation of liquid immersed transformers

As mineral insulating oils as one of the key components of the insulation comprise several risks concerning aging, fire resistance and ecology, the use of ester liquids becomes increasingly attractive, moreover as the price of mineral oil based products continuously escalates. In this contribution a new ester insulating liquid is introduced, that combines the advantages of mineral insulating oils and ecological friendly, low viscosity synthetic liquids. Insulating liquids of mostly synthetic origin like high molecular weight hydrocarbons or silicone oils could so far not substitute mineral oils as their application characteristics are inferior or their price is disproportionate. In Europe only ester liquids, namely Midel 7131, have proven their advantageousness for transformers regarding environmental and aging aspects. The newly developed ester liquid, especially because of its low viscosity is a very promising liquid for use in transformers as cooling and insulation liquid. This contribution presents some experiments on the electrical, dielectrical, chemical and environmental characteristics of this liquid, which have been performed to approve the usability of this liquid for transformers