A Complex Permittivity Based Sensor for the Electrical Characterization of High-Voltage Transformer Oils

Abstract

This work investigates the use of a specially designed cylindrical metal cell, inorder to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV)transformer oil samples. The data are obtained at a wide range of frequencies and operationtemperatures to demonstrate the polarization phenomena and the thermally stimulatedeffects. Such complex permittivity measurements may be utilized as a criterion for theservice life prediction of oil field electrical equipment (OFEE). Therefore, by one set ofmeasurements on a small oil volume, data may be provided on the impending termination,or continuation of the transformer oil service life. The oil incorporating cell, attached to theappropriate measuring units, could be described as a complex permittivity sensor. In thiswork, the acquired dielectric data from a great number of operating distribution networkpower transformers were correlated to corresponding physicochemical ones to demonstratethe future potential employment of the proposed measuring technique.

Keywords

• dielectric spectroscopy
• polarization effects
• transformer oils
• tanδ
• insulation aging