Application of elements of quantum mechanics in analysing AC conductivity and determining the dimensions of water nanodrops in the composite of cellulose and mineral oil

Żukowski, P.; Kierczyński, Konrad; Kołtunowicz, Tomasz N.; Rogalski, Przemysław; Subocz, J.

doi:10.1007/s10570-019-02268-5

Cited by 33 publications

(33 citation statements)

References 33 publications

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“…This condition is satisfied by a composite with the composition of an electrotechnical pressboard impregnated with insulating oil containing nanodrops of water. In relation to such a composite, the model assumptions can be presented as follows [37]:…”

Section: Quantum Mechanics Componentsmentioning

confidence: 99%

“…The use of such a high moisture content in tests is connected with the fact that exceeding the value of about (5.0 ± 0.2)% of the weight may lead to the failure of the transformer [30][31][32]. The analysis of the obtained results was carried out with the use of the direct (DC) and alternating (AC) current hopping conductivity model developed on the basis of the quantum-mechanical electron tunneling phenomenon [33][34][35][36][37]. This model has proven to be excellent for the constant and alternating current analysis of the conductivity of a cellulose, mineral oil, and water nanoparticle composite prepared in a traditional way, i.e., by means of drying, humidifying, and then impregnation [37].…”

Section: Introductionmentioning

confidence: 99%

“…According to the Mott model [39], parameter α ≤ 0.8 does not depend on frequency. From the model of the hopping conductivity for composites of pressboard, mineral oil, and water nanodrops [37], it follows that α(f) is a function of frequency. In the area of intermediate frequencies, the phase shift angle is 0° > φ > −90°.…”

mentioning

confidence: 99%

“…As established in papers [25,29,37,44,45], the relaxation time value should depend on the distance between the nearest potential wells, generated by the nanodrops of water. In this work a relaxation time formula was derived for the conductivity of electron tunneling:…”

mentioning

confidence: 99%

“…In this work it was proven that there is both qualitative and quantitative agreement of experimental results with the model of DC and AC hopping conductivity. This model has been successfully used to analyze frequency and temperature dependence of alternating current conductivity of the electrotechnical pressboard, insulating oil, and nanodrops of water composite for the moisture content range from 1% to 4% of weight [37].…”

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confidence: 99%

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Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

et al. 2020

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This article presents direct σDC and alternating σ(f) current conductivity measurements obtained by the frequency domain spectroscopy (FDS) method on cellulose-transformer oil–water nanoparticle composite with a moisture content of (5.0 ± 0.2)% by weight in a temperature range from 293.15 to 333.15 K with step of 8 K. The uncertainty of temperature maintenance during measurements was below ±0.01 K. The sample was prepared for testing in a manner as close as possible to the cellulose insulation moisturizing process in power transformers. For the analysis of the results obtained, a model of alternating and direct current hopping conductivity was used, based on the quantum phenomenon of electron tunneling between the potential wells and nanodrops of water. It was observed that on the d(logσ)/d(logf)-derived waveforms there was a clear low-frequency maximum, and a tendency to reach the next maximum in the high-frequency area was visible. On this basis it was established that the increase in conductivity takes place in two stages. It was found that the position of σ(f) waveforms in the double logarithmic coordinates is influenced by the temperature dependence both of the conductivity and of the relaxation time of the conductivity. These relationships are described with the appropriate activation energies of the conductivity and relaxation time of conductivity. Based on the analysis of experimental data using Arrhenius diagrams, average values of the activation energy of conductivity ΔWσ ≈ (0.894 ± 0.0134) eV and the relaxation time of conductivity ΔWτσ ≈ (0.869 ± 0.0107) eV were determined. The values were equal within the limits of uncertainty and their mean value was ΔW ≈ (0.881 ± 0.0140) eV. Using the mean value of the activation energy, the frequency dependence of conductivity, obtained at different temperatures, was shifted to 293.15 K. For this purpose, first the waveforms were shifted along the horizontal and then the vertical axis. It was found that after the shift the σ(f) waveforms for the different temperatures overlap perfectly. This means that the shape of the frequency dependence of the conductivity is determined by the moisture content of the pressboard. The position of the waveforms in relation to the coordinates is determined by the temperature relationships of the conductivity and the relaxation time of the conductivity.

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Section: Quantum Mechanics Componentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

et al. 2020

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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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There are no nanodroplets of water in wet oil-impregnated pressboard

Kosmulski

2021

Cellulose

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Application of elements of quantum mechanics in analysing AC conductivity and determining the dimensions of water nanodrops in the composite of cellulose and mineral oil

Cited by 33 publications

References 33 publications

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

Frequency‐Domain Dielectric Response of Insulating Paper with High Humidity

There are no nanodroplets of water in wet oil-impregnated pressboard

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