Environmentally Friendly Electroinsulating Fluids – Perspective Ways
The power transformers play a key role in energy system while inseparable part of their electroinsulating system is insulating fluid. Combination of the suitable fluid with solid absorptive material allows power transmission without power limitation. It is indisputable assets of these devices. Currently is very preferred environmentally friendly behaviour of industrial parts, thus electro-insulating fluids must meet the aspect of good biodegradability without risk of contamination during an eventual contact with the environment. The development of new electroinsulating fluids is focused on selection of appropriate mixtures of synthetic esters and on selection and modification of natural esters. Both ways are subject of research and development and some results are shown in the paper. New substances are confronted with standards and mutually compared in terms of electrical and physical properties. Further limiting property, with regard to work condition, is oxidation stability. The method for verifying oxidation stability is object of interest right now. Specifically, searching for a suitable method for fast and precise determination of its level is objective for proposing a new standard. There are presented two methods which are indicative for properties and are applicable for natural and synthetic esters. Employing of proposed methods will help with evaluation of selected electroinsulating fluid. Another important and limiting aspect for electroinsulating fluid is service life. Its verification is done by long-term tests which create the basis of service life characteristics. These characteristics allow the assessment of the degree of resistance in terms of thermal exposure. Further step in this direction is monitoring of the whole electro-insulating system. Solid cellulose-based material and electro-insulating fluid are combined to the whole system and subjected to voltage exposure. Voltage endurance is one of the key features of the system. The final evaluation of obtained results can help to form an opinion on usability of electroinsulation fluids in practical cases. The biodegradability should be considered.