The effect of moisture content on electrical insulating liquids

During past decades mineral oils were widely used as electrical insulation liquids. Recently there are efforts to protect the environment against the negative impact caused by possible contamination with crude oil products which leads to a search for new perspective insulating liquids. These new liquids might be natural vegetable oils or natural esters respectively. The properties of all applied electrical insulation liquids are strongly determined by presence of water in either free or coupled form. Absorption capacities of the above substances to water are obviously different. While mineral oils can be characterized as relatively quickly absorbing water and thereby reaching saturation, synthetic esters behave differently. In this area, particularly with regard to the electrical properties their behavior is not well described yet. The study of the influence of moisture to the behavior in particular of the electrical properties of these materials is the subject of presented paper.