This paper deals with the measurement and comparison of the current characteristics of the liquid dielectric in the frequency and time domains. The theoretical part contains properties of insulating materials, a description of the impedance spectroscopy method in the frequency domain and IRC analysis. The practical part contains experimental description, used sample of liquid dielectric and analysis of measured results with graphical representation of capacity values and loss factor on frequency and values of charging current over time.
The paper deals with the evaluation of shielding effectiveness of different types of paints, which is recommended as a shielding. There is performed an experiment on the creation of a non-professional shielding paint that could be used as a substitute for the professional shielding paints, that are commonly available on the market. The measurement is performed in the frequency range 0.9 - 6 GHz.
The article deals about magnetic fluids based on a transformer ITO100 oil and about behaviour of these fluids under influence of permanent magnetic field represented by time-current characteristics. The measurements were performed in an anechoic EMC chamber and outside the chamber for comparing the results on the same samples. The main objective was to determine how much is the measurement influenced by external electromagnetic fields that generate around electrical equipment and the impact of higher harmonics in the power supply voltage. The measurement is dependent from orientation of actuating magnetic field, this behaviour mainly shows the effect of nanoparticles structuring during exposition of specimen by magnetic field. These particles also changes polarization processes in fluid influence of nanoparticles concentration contained in the fluid.
initially, people were exposed to radiation originating from Earth and the cosmos, a rapid increase in artificial sources of electromagnetic radiation began at the end of the 20th century. This paper deals with research in electromagnetic shielding field. Experiment in this paper is focused on measurement of shielding effectiveness. Measured object was brick filled with mineral wool. Measurements were made for filled bricks with a thickness of 30 cm, 38 cm, 44 cm and 50 cm. The measurement shows that the shielding effectiveness increases with the increasing thickness of the material.
Electrical insulating materials used in the electric power engineering are exposed to various overvoltage phenomena during operation. Effects of voltage impulses with various front time on the breakdown voltage of the biaxially oriented polypropylene foil were studied. The front time of the test voltage impulses used in the experiment imitates atmospheric overvoltage phenomena in laboratory conditions. It is shown that the change of the front time of the test voltage impulses have no significant impact on the breakdown voltage of the tested biaxially oriented polypropylene foil. Statistical analysis shows that the measured values of breakdown voltage have a normal distribution.
This paper deals with evaluation of shielding effectiveness by measurement in anechoic chamber for combination of shielding paint with building materials. The material used for the experiment was polystyrene POLYFORM with thickness 5 cm, shielding paint YSHIELD HSF 64, water and building glue BauKleber, class C1T. The measurement was performed in the frequency range from 1 GHz to 9 GHz with step 50 MHz
In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported.The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil.Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field.In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy.During the observation no external magnetic field was applied.A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field.It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period.As a result, a visible particle chain was formed at the drop electrical equator.This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids.
In this paper, the thermal ageing of pressboard impregnated with two kinds of insulation liquids is studied by means of frequency domain spectroscopy which involves the measurement of real and imaginary part of complex permittivity as function of frequency. The magnetic nanofluid was composed by mineral transformer oil as carrier liquid, nanoparticles of magnetite and surfactant. The thermal aging test was performed at the temperature 90°C for 1000 hours. Each sample had two variations, with and without copper, which has function catalyst. Then frequency domain spectroscopy was investigated at 40°C for restriction of moisture influence from surrounding. From the data and curves, it can be shown that the undried samples are dried with the aging time and cooper considerably getting worse the imaginary part of complex permittivity. In case of magnetic nanofluid, the colloidal suspension was unstable after 800 hours of the thermal ageing. There was found much more resistance of moisture at the nanofluids than in case of mineral oil impregnated pressboard.
This paper deals with the negative abrasive effect of magnetic nanofluids on paper insulation. Nanofluid with magnetite Fe 3 O 4 nanoparticles and conventional transformer paper was used in the experimental part. The simple degradation device based on magnetic properties of nanofluid for the simulation of fluid flow was constructed. Frequency dependent spectroscopy in 20 Hz - 2 MHz domain for analysis of results was used. Moreover, the analysis of samples under the microscope was additionally carried for detection of paper insulation disruption. The microscopic images were processed in 8-bits scale of grey and analysed by a software tool. The results of the experiment indicate the possible negative effect of nanoparticles on cellulose fibres.
Presented article discusses the impact of electromagnetic radiation on dielectric properties of magnetic fluids based on transformer oil ITO 100. For measurements and evaluation of the samples we used the PDC analysis. The measurements were performed in two variants, specifically when individual samples were irradiated and were not irradiated with the external magnetic field. To minimize undesired electromagnetic fields, the measurements were realized in the anechoic EMC chamber. The main objective of this experiment was to determine if the electromagnetic radiation can change properties of magnetic liquid. Used samples of magnetic fluids were with different concentrations of magnetic nanoparticles. In the experiment was generated electromagnetic field, used to charge and discharge streams, of which are indicative of the state of the insulation system. For comparison of the results the samples were analyzed before irradiation with EM field and after irradiation with EM field.
