Frequency-Dependent Dielectric Spectroscopy of Insulating Nanofluids Based on GTL Oil during Accelerated Thermal Aging

Abstract

Improving the dielectric properties of liquid-insulating materials is a current problem in research into the insulation system of a power transformer. Modern optimization of insulating liquids involves the potential use of unique synthetic esters enriched with nanoparticles. This study presents the results of the dielectric response of liquefied gas-based (GTL) insulating liquids during accelerated thermal aging. The dielectric relaxation spectroscopy method was used in the frequency domain to point out power losses as an imaginary part of a complex electric modulus. The relaxation spectra express the validity of applying this complex dielectric parameter. The polarization processes of the base oil alternately change position in the low-frequency band during thermal aging. Fullerene nanofluid undergoes three phases of dielectric loss changes during thermal aging. In the case of magnetic nanofluid, the effect of electric double-layer polarization disappeared after 500 h of thermal aging. It was found that with the gradual increase in the thermal aging time, there is no gradual increase in the dielectric losses investigated in the measured frequency spectrum. This study shows that the concentration of the two types of nanoparticles independently causes a different dielectric response to an applied AC electric field in the GTL base fluid.

A Comprehensive Study of Polyurethane Potting Compounds Doped with Magnesium Oxide Nanoparticles

“…Broadband dielectric spectroscopy (BDS) has been used to analyse the material response to alternating electric fields with variable frequency f (Hz), allowing the study of the behaviour of dielectric materials and the characterization of the individual contributions of polarization processes, which can be defined based on changes due to various factors [ 60 , 61 ]. A modular measurement system was used with an Alpha A mainframe (Novocontrol Technologies, Montabaur, Germany) and a ZGS test interface.…”