Comparative evaluation of alternative fluids for power transformers

The demands on the power supply are increasing continuously, and it seems that this trend will not change in the near future. Power transformers are used in power systems where there is a transition between voltage levels. For this reason, transformers are one of the most strategic components for electric powergeneration, transmission and distribution. Many users prefer oil-filled transformers to the dry-type because dielectric oils cool and insulate. In this type of transformer, the combination of a solid (cellulose) and a liquid insulation (naphthenic mineral oil) is the most frequently used insulating system. Although mineral oil has been widely used, it does not meet health and current environmental laws because it is not biodegradable. In addition, mineral oil presents high fire risk, which becomes a serious problem for safety in electrical facilities. All of these drawbacks have encouraged the search for alternative fluids such as organic esters. This work compares the main properties of alternative liquids to show their possibilities for naphthenic oil replacement. The development of dielectric fluids based on vegetable oils is also described. The advantages of these liquids over mineral oil are discussed. (C) 2013 Elsevier B.V. All rights reserved.