Dielectric spectroscopy and gas chromatography methods applied on high-voltage transformer oils

This paper points out the advantages offered by the temperature dependent dielectric spectroscopy in frequency domain, as an additional diagnostic technique for insulation testing of power transformers for life-time prediction. Complex permittivity measurements have been carried out as a function of operating frequency and oil temperature for a wide selection of high voltage transformers and the gaseous byproduct concentrations were also monitored. The work correlates dielectrometry data to the gas chromatography ones