“…El-Saied et al. [ 28 ] found that dipole orientation polarization could be present in some materials at frequencies up to 1010 Hz while electronic and ionic polarizations, still existed below 1013 Hz ( Figure 4 ). Figure 4 Relative permittivity (ε′) and corresponding tan δ as a function of Log (f) at room temperature for different VPCs and TiO 2 /CMC ratios: (a) 90%TiO 2 /10% MCC, (b) 75%TiO 2 /25% MCC, (c) 50%TiO 2 /50% MCC and (d) 25%TiO 2 /75% MCC.…”
Section: Resultsmentioning
confidence: 99%
“…The variation of the dielectric constant ε 0 with frequency has already been used to determine the type of polarization occurring in a material. El-Saied et al [28] found that dipole orientation polarization could be present in some (Figure 4).…”
Section: Dielectric Properties Of Compositesmentioning
In this study, various composite films were prepared by varying the amounts of long-oil Alkyd Resin (AR), Titanium Dioxide (TiO 2) and Microcrystalline Cellulose (MCC). The effects of each component, TiO 2 and MCC, on the properties and microstructure of the dry film were determined by examining images obtained by scanning electron microscopy (SEM) and studying the evolution of dielectric properties, the dielectric constant and the loss factor, against frequency at room temperature. Results showed that the introduction of the TiO 2 /MCC powder with a weight ratio larger than 1 and a volumetric pigment concentration (VPC) less than 50% allowed a better dispersion of the particles and fitted well the Linchtencker logarithmic mixing law and the Maxwell-Garnett theory. Finally, a marked improvement of the dielectric constant with respect to those of pure alkyd resin and AR/TiO 2 composites was observed.
“…El-Saied et al. [ 28 ] found that dipole orientation polarization could be present in some materials at frequencies up to 1010 Hz while electronic and ionic polarizations, still existed below 1013 Hz ( Figure 4 ). Figure 4 Relative permittivity (ε′) and corresponding tan δ as a function of Log (f) at room temperature for different VPCs and TiO 2 /CMC ratios: (a) 90%TiO 2 /10% MCC, (b) 75%TiO 2 /25% MCC, (c) 50%TiO 2 /50% MCC and (d) 25%TiO 2 /75% MCC.…”
Section: Resultsmentioning
confidence: 99%
“…The variation of the dielectric constant ε 0 with frequency has already been used to determine the type of polarization occurring in a material. El-Saied et al [28] found that dipole orientation polarization could be present in some (Figure 4).…”
Section: Dielectric Properties Of Compositesmentioning
In this study, various composite films were prepared by varying the amounts of long-oil Alkyd Resin (AR), Titanium Dioxide (TiO 2) and Microcrystalline Cellulose (MCC). The effects of each component, TiO 2 and MCC, on the properties and microstructure of the dry film were determined by examining images obtained by scanning electron microscopy (SEM) and studying the evolution of dielectric properties, the dielectric constant and the loss factor, against frequency at room temperature. Results showed that the introduction of the TiO 2 /MCC powder with a weight ratio larger than 1 and a volumetric pigment concentration (VPC) less than 50% allowed a better dispersion of the particles and fitted well the Linchtencker logarithmic mixing law and the Maxwell-Garnett theory. Finally, a marked improvement of the dielectric constant with respect to those of pure alkyd resin and AR/TiO 2 composites was observed.
“…Presspaper is widely used in transformers because of the advantages of excellent performance, low cost, and environmental friendliness [ 1 , 2 , 3 ]. However, the complex and severe electric field of valve winding of converter transformers causes considerable failures of existing oilpaper materials [ 4 , 5 , 6 ], threatening the reliability of the power supply.…”
Nanocellulose-modified presspaper is a promising solution to achieve cellulose insulation with better performance, reducing the risk of electrical insulation failures of a converter transformer. Predicting the dielectric properties will help to further design and improvement of presspaper. In this paper, a multivariable method was adopted to determine the effect of softwood fiber on the macroscopic performance of presspaper. Based on the parameters selected using the optimum subset method, a multiple linear regression was built to model the relationship between the fiber properties and insulating performance of presspaper. The results show that the fiber width and crystallinity had an obvious influence on the mechanical properties of presspaper, and fiber length, fines, lignin, and nanocellulose had a significant impact on the breakdown properties. The proposed models exhibit a prediction accuracy of higher than 90% when verified with the experimental results. Finally, the effect of nanocellulose on the breakdown strength of presspaper was taken into account and new models were derived.
“…The life span of transformers is basically determined by physicochemical, electrical and mechanical characteristics of their insulation system [6,7]. This insulation system generally consists of two types of materials, liquid and solid [8].…”
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