Electrode polarization and unusual magnetodielectric effect in a transformer oil-based magnetic nanofluid thin layer

2017 ◽  
Vol 146 (1) ◽  
pp. 014704 ◽  
Author(s):  
Michal Rajnak ◽  
Bystrik Dolnik ◽  
Juraj Kurimsky ◽  
Roman Cimbala ◽  
Peter Kopcansky ◽  
...  
Keyword(s):  
Thin Layer ◽  
Transformer Oil ◽  
Electrode Polarization ◽  
Magnetic Nanofluid ◽  
Magnetodielectric Effect

Transformer oil-based magnetic nanofluid with high dielectric losses tested for cooling of a model transformer

2019 ◽  
Vol 26 (4) ◽  
pp. 1343-1349 ◽  
Author(s):  
Michal Rajnak ◽  
Milan Timko ◽  
Peter Kopcansky ◽  
Katarina Paulovicova ◽  
Jozef Kuchta ◽  
...  
Keyword(s):  
Transformer Oil ◽  
Dielectric Losses ◽  
Magnetic Nanofluid ◽  
High Dielectric

scholarly journals Prediction of Moisture and Aging Conditions of Oil-Immersed Cellulose Insulation Based on Fingerprints Database of Dielectric Modulus

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1722
Author(s):  
Yiyi Zhang ◽  
Sheng Li ◽  
Xianhao Fan ◽  
Jiefeng Liu ◽  
Jiaxi Li
Keyword(s):  
Low Frequency ◽  
Degree Of Polymerization ◽  
Transformer Oil ◽  
Electrode Polarization ◽  
Insulation System ◽  
Dielectric Modulus ◽  
Aging Conditions ◽  
Fingerprint Database ◽  
Cellulose Insulation ◽  
Potential Tool

Frequency-domain spectroscopy (FDS) is demonstrated to be affected by electrode polarization and conductance behavior in the low-frequency ranges, which causes the unreliable prediction results of transformer cellulose insulation. In order to solve this issue, a fingerprint database based on the dielectric modulus is reported to predict the degree of polymerization (DP) and moisture content of cellulose insulation. In the current work, the relevant fingerprints that characterize the insulation conditions are obtained by studying the dielectric modulus curves of cellulose insulation with various insulation conditions, as well as the DC conductivity of transformer oil. Then, the dielectric modulus fingerprint database is established in the lab, and the accuracy of the reported fingerprint database is later verified. As a potential tool, the dielectric modulus fingerprint database is tested by several samples, and the results demonstrate that the accuracy of this method is more than 80%. In that respect, an interesting discovery of this paper is that the dielectric modulus fingerprint database may be a helpful tool for conditions prediction of the transformer cellulose insulation system.

scholarly journals Magnetic Field Effect on Thermal, Dielectric, and Viscous Properties of a Transformer Oil-Based Magnetic Nanofluid

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4532 ◽  
Author(s):  
Michal Rajnak ◽  
Zan Wu ◽  
Bystrik Dolnik ◽  
Katarina Paulovicova ◽  
Jana Tothova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Volume Fraction ◽  
Effective Medium Theory ◽  
Transformer Oil ◽  
Dielectric Anisotropy ◽  
Magnetic Nanofluid ◽  
Conductivity Sensor ◽  
Anisotropic Thermal Conductivity ◽  
Transformer Oils

Progress in electrical engineering puts a greater demand on the cooling and insulating properties of liquid media, such as transformer oils. To enhance their performance, researchers develop various nanofluids based on transformer oils. In this study, we focus on novel commercial transformer oil and a magnetic nanofluid containing iron oxide nanoparticles. Three key properties are experimentally investigated in this paper. Thermal conductivity was studied by a transient plane source method dependent on the magnetic volume fraction and external magnetic field. It is shown that the classical effective medium theory, such as the Maxwell model, fails to explain the obtained results. We highlight the importance of the magnetic field distribution and the location of the thermal conductivity sensor in the analysis of the anisotropic thermal conductivity. Dielectric permittivity of the magnetic nanofluid, dependent on electric field frequency and magnetic volume fraction, was measured by an LCR meter. The measurements were carried out in thin sample cells yielding unusual magneto-dielectric anisotropy, which was dependent on the magnetic volume fraction. Finally, the viscosity of the studied magnetic fluid was experimentally studied by means of a rheometer with a magneto-rheological device. The measurements proved the magneto-viscous effect, which intensifies with increasing magnetic volume fraction.

Electrical conduction in a transformer oil-based magnetic nanofluid under a DC electric field

2018 ◽  
Vol 459 ◽  
pp. 191-196 ◽  
Author(s):  
Michal Rajnak ◽  
Milan Timko ◽  
Juraj Kurimsky ◽  
Bystrik Dolnik ◽  
Roman Cimbala ◽  
...  
Keyword(s):  
Electric Field ◽  
Electrical Conduction ◽  
Transformer Oil ◽  
Magnetic Nanofluid ◽  
Dc Electric Field

scholarly journals Study of the sorption properties of solvents in thinlayer and column chromatography

2020 ◽  
Vol 22 (2) ◽  
pp. 19-26
Author(s):  
Vu Ngoc Dan ◽  
V. F. Novikov
Keyword(s):  
Liquid Chromatography ◽  
Thin Layer ◽  
Ethyl Acetate ◽  
Thin Layer Chromatography ◽  
Methyl Ethyl Ketone ◽  
Retention Time ◽  
Boiling Point ◽  
Transformer Oil ◽  
Methyl Ethyl ◽  
Layer Chromatography

Much attention is paid to the consideration of the causes of transformer oil aging under the influence of technogenic and natural factors. The paper insulation destruction mechanism is considered, as a result of which furan compounds are formed that enter the transformer oil and worsen its dielectric characteristics. The characteristics of the domestic transformer oil grade GK-1 obtained using the technology of hydrocracking in a hydrogen medium are given. Furan compounds are formed in used transformer oil, which are monitored using chromatographic analysis methods according to standard procedures. The group composition of transformer oil was determined using thin layer chromatography. As a solvent used n. Hexane. To extract furan compounds from transformer oil, various organic solvents are used, the physicochemical properties of which are given in this work. It was found that the retention time of the studied sorbates corresponds to an increase in their boiling points for ethyl acetate, methyl ethyl ketone and dodecane. In the case of isopropanol, which has a close boiling point with ethyl acetate and methyl ethyl ketone, a significant increase in retention time is observed, which is associated with the formation of an intermolecular hydrogen bond. The dependence of the spot diameter of furan substances on their concentration was established under conditions of thin-layer chromatography on Sorbfil plastics. Moreover, the most effective separation is characteristic of furfural. In this case, the chromatographic spots are small in size with good fidelity. The ascending mode of column liquid chromatography was used to determine the dependence of the retention time of standard sorbates on the length of the Silyochrome S-80 sorption layer, which is parabolic. It was found that the highest retention times are characteristic of ethoxyethanol and isopropanol, which is consistent with the known theoretical principles of liquid chromatography. Histograms of the effect of the retention time of standard sorbates on their nature and boiling point, where isopropanol and 2-ethoxyethanol are extreme, are presented. In this case, isopropanol having a lower boiling point than 2-Ethoxyethanol is retained on the sorbent more strongly, which is associated with the formation of intermolecular hydrogen bonds with surface silanol groups of the sorbent.

scholarly journals Experimental investigation on the burning behaviors of thin-layer transformer oil on a water layer

2020 ◽  
Vol 139 ◽  
pp. 89-97
Author(s):  
Jinlong Zhao ◽  
Jianping Zhang ◽  
Changkun Chen ◽  
Hong Huang ◽  
Rui Yang
Keyword(s):  
Experimental Investigation ◽  
Thin Layer ◽  
Water Layer ◽  
Transformer Oil

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

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