Transformer mineral oil contains a mixture of different hydrocarbons but is generally composed of three main components: alkanes, cycloalkanes and aromatic hydrocarbons. Alkanes include saturated linear (normal) and branched (iso-) alkanes, cycloalkanes with side hydrocarbon chains and aromatic hydrocarbons contain unsaturated discrete or condensed aromatic rings that may have side alkyl-or cycloalkyl substituents
