Chemometric evaluation of synchronous scan fluorescence spectroscopy for the determination of regulatory conformance and usage history of insulation oils

This paper describes the evaluation of synchronous scan fluorescence spectroscopy as a means of determining key characteristics of mineral insulating oils that are used in electrical apparatus around the world. Characteristics of interest to commercial operators include regulatory conformance, the history of the oil (whether it has been used or not), and, ideally, the identity and manufacturer of the oil. The oils analyzed in this study are highly relevant to real applications as they were acquired from actual high voltage power transformers operated in the United Kingdom (UK) or from stocks intended for future use in transformers. A small number of foreign oils that do not conform to UK regulations were also analysed. Principal components analysis (PCA) is used to evaluate the usefulness of the information contained in the acquired fluorescence spectra. This reveals that oils from different manufacturers can exhibit different types of spectra and that it may be possible to determine the identity of an oil from its spectral characteristics. It is also found that the spectra can be used to determine whether or not an oil has been used and whether it meets British regulatory standards. It is concluded that synchronous scanning fluorescence spectroscopy, combined with appropriate chemometrics, could provide the basis for a rapid screening test, capable of indicating whether or not a particular new or used transformer oil is suitable for initial use or continued use in high voltage equipment.