Temperature dependent dielectric spectroscopy in frequency domain of high-voltage transformer oils compared to physicochemical results

The temperature dependent dielectric spectroscopy in frequency domain is compared to physicochemical and electrical tests that are periodically applied on highly insulating transformer oils. Complex permittivity and tan/spl delta/ data are obtained as a function of frequency and operation temperatures, to demonstrate the polarization phenomena and the induced loss intensification by the thermally stimulated currents. The acquired dielectric data of oil samples collected from 201 operating HV power transformers, were correlated to their corresponding physicochemical ones in order to demonstrate the future potential employment of the proposed measuring technique in the field of high voltage engineering towards reliability monitoring of oil filled electrical equipment (OFEE).