Permittivity of a composite of cellulose, mineral oil, and water nanoparticles: theoretical assumptions

Żukowski, P.; Kołtunowicz, Tomasz N.; Kierczyński, Konrad; Rogalski, Przemysław; Subocz, J.; Szrot, M.; Gutten, Miroslav; Šebök, Milan; Jurcik, Jozef

doi:10.1007/s10570-015-0797-6

Cited by 45 publications

(13 citation statements)

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“…Another drawback of Debye's model is the reduction of dielectric permittivity in a square frequency function. Measurements of dielectric permittivity of impregnated pressboard with a certain moisture content prove that these relationships are weaker ( _ Zukowski et al 2016). In order to justify the presence of weaker than square dependences on the frequency conductivity and dielectric permittivity, a number of empirical models Cole 1941, 1942;Havriliak and Havriliak 1997) were developed.…”

Section: Introductionmentioning

confidence: 99%

“…In ( _ Zukowski et al 2014( _ Zukowski et al , 2015c( _ Zukowski et al , 2016 for the analysis of relaxation processes of the DC conductivity and permittivity of the AC conductivity in the composite cellulose-mineral oil-water nanoparticles a new approach is used, based on taking into account the occurrence of an hopping exchange (tunnelling) of electrons between wells of potential generated by the water nanoparticles. It was agreed that in the composite cellulose-mineral oil-water nanoparticles there are complex depenednces of AC conductivity and dielectric permittivity on temperature, frequency and moisture, which are reviewed in studies ( _ Zukowski et al 2015c( _ Zukowski et al , 2016. However, the application of the AC conductivity and dielectric permittivity to assess the moisture level of the solid insulation of power transformers requires fairly complex calculations of the measured frequency resistance and capacitance, taking into account the geometric dimensions of the insulation.…”

Section: Introductionmentioning

confidence: 99%

“…Similar results were obtained for pressboard with the moisture content of 1, 2, and 3 wt%. Therefore, we selected as a reference, just as in ( _ Zukowski et al 2015c( _ Zukowski et al , 2016, the inflection point on the log{tgd(logf)} function, which, as can be seen from Fig. 1, lies in the frequency region much lower than the local minimum, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric losses in the composite cellulose–mineral oil–water nanoparticles: theoretical assumptions

et al. 2016

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The paper presents an analysis of test results by Frequency Domain Spectroscopy (FDS) of the loss tangent (tgd) in electrotechnical pressboard impregnated with insulating oil and containing nanoparticles of water depending on the frequency of alternating current, sample temperature and degree of moisture. We found tgd reduction in areas of low and ultra-low frequency. It is associated with relaxation due to the hopping conductivity (tunnelling) of electrons between moisture nanoparticles occurring in the cellulose impregnated with insulating oil. In frequency areas close to the local minimum of tgd and higher, relaxation does not depend on the moisture content and is associated with other polar molecules which are part of the cellulose. We developed a new method converting experimental frequency dependence of the loss angle tangent, measured by the FDS method to the reference temperature of 293 K (20°C), using the exponential dependence of the relaxation time on the temperature, was developed. The activation energy of the relaxation time was determined based on the loss angle tangent of moist electrotechnical pressboard impregnated with insulating oil. It was found that the variation in moisture content in the composite cellulose-mineral oil-water nanoparticles do not cause changes in the activation energy of the relaxation time. The conversion of experimental frequency dependence of the loss angle tangent determined by the FDS method to the reference temperature of 293 K (20°C) eliminates the temperature dependence in the areas of ultra-low and low frequencies occurring in the runs made directly on the basis of the measurement results. After calculating the frequency dependence of the loss angle tangent to the reference temperature, all that remains is its dependence on the moisture content.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dielectric losses in the composite cellulose–mineral oil–water nanoparticles: theoretical assumptions

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“…The activation energy E A can be calculated utilizing linear approximation of the Arrhenius temperature graph [24], applying the following dependencies:…”

Section: Pdc Methodsmentioning

confidence: 99%

“…Using the sample depolarization current characteristics depending on the measurement temperature, it was decided to analyze, using Equations (1)-(4), the dependence of the activation energy EA on the degree of moisture of the cellulose-aramid insulation. Figure 10 presents the manner of fixing characteristic time tA (Figure 10a) and the activation energy EA value (Figure 10b) with the use of the Arrhenius graph [24] for a selected non-aged sample with the smallest degree of moisture. The result of calculation of the activation energy EA depending on moisture for a selected The measurement temperature growth (Figure 9b) also reduced the differences between the depolarization currents of samples with various moisture degrees within approx.…”

Section: Effect Of the Degree Of Moisturementioning

confidence: 99%

Analysis of Polarization and Depolarization Currents of Samples of NOMEX®910 Cellulose–Aramid Insulation Impregnated with Mineral Oil

Wolny

Krotowski

2020

Energies

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The article presents results of laboratory tests performed on samples of NOMEX®910 cellulose–aramid insulation impregnated with Nynas Nytro 10× inhibited insulating mineral oil using the polarization and depolarization current analysis method (PDC Method). In the course of the tests, the insulation samples were subjected to a process of accelerated thermal degradation of cellulose macromolecules, as well as weight-controlled dampening, thereby simulating the ageing processes occurring when using the insulation in power transformers. The effects of temperature in the ranges typical of normal transformer operation were also taken into account. On the basis of the obtained data, the activation energy was then fixed together with dominant time constants of cellulose–aramid insulation relaxation processes with respect to the temperature and degree of moisture, as well as thermal degradation of cellulose macromolecules. It was found that the greatest and predictable changes in the activation energy value were caused by the temperature and the degree of moisture in the samples. A similar conclusion applies to the dominant time constant of the relaxation process of cellulose fibers. Degree of thermal degradation samples was of marginal importance for the described parameters. The final outcome of the test results and analyses presented in the article are regression functions for the activation energy and the dominant time constants depending on the earlier listed parameters of the experiment, which may be used in the future diagnostics of the degree of technical wear of cellulose–aramid insulation performed using the PDC method.

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Frequency‐Domain Dielectric Response of Insulating Paper with High Humidity

Tu,

Wang,

Chen

et al. 2023

IEEJ Transactions Elec Engng

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The frequency‐domain dielectric spectroscopy (FDS) of humid insulating paper has been measured at different temperatures. The data show three independent dielectric processes: electrode polarization, hopping conductivity and interfacial polarization. The dielectric properties of humid insulating paper are composed of hopping conductivity and interfacial polarization, and its equivalent dielectric model can be represented by a Havriliak‐Negami (HN) relaxation branch parallel hopping conductivity. At high temperatures and low frequencies, the measured dielectric spectroscopy bends downward, which is caused by the electrode polarization. In this case, the equivalent dielectric model is composed of the body impedance of insulating paper and the electrode polarization in series. According to the equivalent dielectric model, the components of electrode polarization, hopping conductivity, and interface polarization can be separated, thereby eliminating the parasitic effect of electrode polarization on the dielectric properties of insulating paper. Both of hopping conductivity and interface polarization of insulating paper move toward high‐frequency direction with temperature increasing. For humid insulating paper with a moisture content of 5.9%, the activation energies of hopping conductivity and interface polarization are 1.18 and 0.99 eV, respectively. This difference in activation energies results in the inability of the spectrums of insulating paper to overlap with each other at different temperatures. Based on the insulating paper without oil immersion, the results obtained in this article are not affected by oil or oil‐immersion operations. This provides a reference for exploring the dielectric properties and physical mechanisms of oil‐paper composite insulation materials widely used in high‐voltage equipment. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

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Permittivity of a composite of cellulose, mineral oil, and water nanoparticles: theoretical assumptions

Cited by 45 publications

References 23 publications

Dielectric losses in the composite cellulose–mineral oil–water nanoparticles: theoretical assumptions

Dielectric losses in the composite cellulose–mineral oil–water nanoparticles: theoretical assumptions

Analysis of Polarization and Depolarization Currents of Samples of NOMEX®910 Cellulose–Aramid Insulation Impregnated with Mineral Oil

Frequency‐Domain Dielectric Response of Insulating Paper with High Humidity

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