Examination of Insulating Oils for Transformers by Instrumental Methods

In this paper it is suggested that gas chromatographic (GC) fingerprints could be very useful in identification and source recognition of insulating oils produced by any particular producer, samples from unmarked drums, or from different stocks of the same producer. According to the described fingerprinting method, the insulating oil samples are characterized on the basis of the contours of their easily obtainable chromatograms, composed of a number of small peaks, as well as the profiles of these chromatograms. The method is particularly discussed relative to the infrared (IR) ASTM method D 2144/66, which is generally recommended for the examination of insulating oils in a fingerprint region. The usefulness of liquid chromatography (LC) fingerprints as auxiliary and complementary data is also pointed out. Finally, it is demonstrated that GC fingerprints, with assistance of IR spectra and LC fingerprints, represent a reliable basis for indicating changes in the crude oil type or changes in the refining process and blending of insulating oils.