Abstract
The influence of different concentrations (0.5, 1.0, and 2.0 wt.%) of Zinc Oxide (ZnO) filler on the dielectric properties of the cold-curing polyurethane (PU) resin is presented in this study. For this purpose, the direct DC conductivity and the broadband dielectric spectroscopy measurements were used to describe the changes in dielectric responses of PU/ZnO nanocomposites over the frequency and temperature range, respectively. It can be stated that, the 1.0 wt.% nanoparticles and lower caused a decrease in the real relative permittivity compared to the pure PU resin, while the higher concentration of nanoparticles for frequencies above 1 Hz had the opposite effect. The presence of nanoparticles in the polyurethane resin affected the segmental dynamics of the polymer chain and changed a charge distribution in the given system. These changes caused a shift of local relaxation peaks in the spectra of imaginary permittivity and dissipation factor of nanocomposites. It is suggested that the temperature-dependent transition of the electric properties in the nano-composite is closely associated with the -relaxation and intermediate dipolar effects (IDE).
Highlights
For the safe and reliable operation of any electrical device, it is necessary to set up specific dielectric, thermal, and mechanical parameters of the used electro-insulating materials.Insulation systems of modern electrical equipment are exposed to higher operation and environmental stresses than before [1], but at the same time, higher reliability and longer technical lifetime are required
Polyurethane nanocomposites with various concentrations of Zinc Oxide (ZnO) nanoparticles were studied by the broadband dielectric spectroscopy
The complex dielectric permittivity, dissipation factor, and DC electrical conductivity of the nanocomposites were measured in the temperature range from 20–120 °C. 0.5 and 1.0 wt.% nanoparticles caused a decrease in the real permittivity as pure PU resin
Summary
For the safe and reliable operation of any electrical device, it is necessary to set up specific dielectric, thermal, and mechanical parameters of the used electro-insulating materials.Insulation systems of modern electrical equipment are exposed to higher operation and environmental stresses than before [1], but at the same time, higher reliability and longer technical lifetime are required. In the case of the transformers, many of the in-operation transformers around the world are closed to, or beyond their designated technical life. Their operational reliability and predicted lifetime is strongly dependent on the construction and condition of their insulation system [2,3,4]. Their technical life is reduced by the current higher loads and loads changes due to employing more and more distributed renewable energy sources to the old power networks. The available transformer failure statistics are showing, that the average age of the transformers, which fails due to insulation damage is
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