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1
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The Application of the Correlative Analysis and the Regression Function for Determining Correlations οf the Measurement Results of Acoustic Emission Generated by Partial Discharges

100%
Boczar T., Frącz P.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
281-284
EN
The subject matter of this paper is connected with development of the assessment methods of results obtained at measurements of partial discharges occurring in insulation systems of power transformers using the acoustic emission method. The paper presents the results connected with determining correlation between partial discharge generation voltage and selected descriptors characterizing the emitted signals of acoustic emission in the frequency domain. Authors use the selected descriptors as comparative criteria for recognition of the basic partial discharge forms that may occur in paper-oil insulation of power transformers. The correlation coefficient and regression function were used to determine the correlation degree between the variables under study.
2
Content available remote

Characteristic of Surface Partial Discharges Measured with Ultraviolet Camera

81%
Frącz P., Zmarzły D., Boczar T.
Acta Physica Polonica A
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2015
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vol. 127
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issue 3
715-718
EN
The performed research works consider diagnosis of different models of support and bushing insulators. Insulator systems undergo aging processes, which causes deterioration of the insulating properties. In addition, pollutants that accumulate on the surface of high voltage insulators cause further reduction of the insulation properties. Presence of pollutants and high humidity level cause formation of conductive paths, which acts as a source of partial discharges. Presented results depict optical signals, recorded by ultraviolet camera, which were emitted by surface partial discharges occurring on different insulator models. In particular, the effect of the relative value of camera sensitivity on the number of surface partial discharges counts was evaluated. In addition, analysis of the effect of the surface partial discharges generation time on registered counts number was made. The experiments were performed at a constant voltage of 0.9U_{p} and for a distance between the HV electrode and GND equal to 10 cm. The experimental study lasted over a period of 30 min, while the measurement steps were done every minute.
3
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Studies on Infrasound Noise Generated by Operation οf Low-Power Wind Turbine

81%
Pierzga R., Boczar T., Wotzka D., Zmarzły D.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
542-545
EN
Subject matter of this paper deals with issues of the environmental impact of infrasound noise associated with operation of low-power wind turbines. It is now the current and relevant problem for both the cognitive and utilitarian standpoint. There is now a considerable growth in the number of such installations in Poland, Europe and in the world, due to the possibility of locating them on existing building roofs in heavily urbanized areas, and without having to build additional supporting structures. As part of the study, measurements of low frequency acoustic signals generated during operation of micro turbine equipped with a rotor of vertical axis of rotation relative to the wind direction have been performed. Analyses were carried out in order to determine the impact of wind speed and selected meteorological parameters on the level of infrasound signals emitted by the test turbine. In addition, frequency analysis of the recorded signals was performed. Then, the obtained results were subjected to comparative analysis. In summary, the achieved results were referred to the limits of sound pressure intensity level of infrasound signals as specified for the working environment in accordance with the Polish Standard PN-Z-01338.
4
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Studies on Infrasound Noise Emitted by Wind Turbines of Large Power

81%
Boczar T., Malec T., Wotzka D.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
850-853
EN
The subject area of this article applies to study of infrasound signals generated by the work of modern wind turbines. Infrasound noise measurements were conducted in accordance with assumptions of the EN 61400-11 standard. The object of study was a newly commissioned wind farm with a total electrical power equal to 30 MW. The considered power station consisted of 15 new wind turbines, each with a capacity of 2 MW. Scope of the analysis performed included designation of time runs, depicting temporal changes, and designation of frequency spectra of the recorded infrasound signals. Evaluation of the impact of changes in wind speed was made. Moreover, the scope of analysis, performed in this field, concerned assessment of the impact on the obtained results values of meteorological parameters related to the applied measurement system. Values obtained from measurements were related to and compared with the limits specified in standards and regulations existing in this field.
5
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Solving a Set of Spherical Equations for Localization of Partial Discharges by Acoustic Emission Method

81%
Boczar T., Witkowski P., Borucki S., Cichoń A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 3
299-305
EN
This article deals with the subject matter of improvement of the acoustic emission methods used for location of partial discharges, which may occur inside power transformer insulation systems. Analytical solutions of spherical equations for location of partial discharge generation using the acoustic method were shown in detail. Presented in the article method of solving the assumed equations is based on the analytical method and matrix notation. Theoretical considerations and later the measurement-based verification refer to the use of the triangulation method for location of the occurrence of partial discharges. The results of the scientific and research works that have been presented in this article are the next stage of research aimed at development of on-line diagnosis system for insulation systems of electrical equipment, allowing for detection, measurement and identification of forms and locations of partial discharges using the acoustic emission method.
6
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Diagnostics of the Core Mechanical Construction Based on Vibroacoustic Measurements and Distribution of Temperature Field in Transformer Magnetic Circuit

81%
Borucki S., Cichon A., Boczar T.
Acta Physica Polonica A
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2015
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vol. 128
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issue 3
306-309
EN
Subject matter of this article concerns the results of research works on the development and use of the vibroacoustic method to evaluate technical state of transformer cores. The article presents obtained measurement results of transformer mechanical vibration for two cases of its operation: with twisted and loosened core. In order to demonstrate negative effects of operating a transformer with a loosened core, this publication presents thermographic images showing temperature distribution on its magnetic core. The article characterises the examined transformer, employed measurement system and methodology of the completed experiment. The vibroacoustic and thermographic measurements were carried out during idle work of the transformer. Core vibration was registered for three measurement axes: 0X, 0Y and 0Z. Completed tests have proven that loosened screws pressing the core cause evident increase in the value of magnetic core vibration acceleration. At the same time, the temperature rises by more than 25%.
7
Content available remote

Analysis of Acoustic Wave Propagation in a Power Transformer Model

81%
Wotzka D., Boczar T., Zmarzły D.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
428-431
EN
Analyses of acoustic wave propagation in a model power transformer are presented in the paper. The acoustic wave is induced by partial discharges that are simulated at predefined coordinates in the core and winding. Propagation of the numerical calculated acoustic wave is analyzed within the transient state. Achieved results indicate that the space and time distributions of the acoustic pressure depend on the induction position. Furthermore, a greater pressure gradient is observed in domains with higher speed of sound while the largest amplitude occurs at the vicinity of the induction position.
8
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Analysis of Acoustic Signals Interfering Diagnostic Measurements of Electric Power Transformer Tap Changers

81%
Boczar T., Cichoń A., Borucki S., Szczyrba T.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
387-390
EN
Subject matter of this paper applies to improvement of acoustic emission method used in the diagnosis of on load tap changers of high power transformers. During measurement of acoustic emission signals generated by damages or defects, which can appear in insulation system and in the power transformer tap changers, various forms of noise signals may occur. Interferences occurring during measurements under laboratory and under industrial conditions can be generated either by sources placed inside the studied electric power device or they can be emitted in their immediate vicinity. Sources of interfering signals are physical phenomena of a mechanical, electrical or acoustical nature. Interferences appearing during measurement of acoustic emission pulses generated by electrical discharges and other types of defects that overlap the measured waveforms may result in their distortion. As part of the research conducted, the results of which are presented in this paper, following was subjected under consideration: measurements of acoustic noise signals generated by partial surface discharges occurring on support and bushing insulators were performed.
9
Content available remote

Measurements and Acoustic Analyses of Infrasound Noise Emitted by Operation of Small, Building Mounted Wind Farm

81%
Pierzga R., Boczar T., Wotzka D.
Acta Physica Polonica A
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2015
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vol. 128
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issue 3
294-298
EN
Operation of modern wind turbines generates infrasound noise which is known as potentially harmful for humans. In presented study, measurements of infrasound noise generated by operation of five vertical axis, building mounted, small wind turbines were conducted. Measurements were taken in urban area at several points and different distances from the installation. Analyses were performed to determine the level of emitted infrasound noise in vicinity of the installation. Comparative analyses were carried out and the achieved results were referred to the limits of sound pressure intensity level of infrasound signals as specified for the working environment in accordance with the Polish standard PN-Z-01338.
10
Content available remote

Analysis of Ionizing Radiation Generated by Partial Discharges

81%
Zmarzły D., Nagi Ł., Borucki S., Boczar T.
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vol. 125
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issue 6
1377-1379
EN
This paper presents the preliminary results of the performed experiment, based on common phenomenon of partial discharges. A simple Geiger-Muller counter (DP-66M) was used for measurement of a dose of ionizing radiation, which is accompanied by partial discharges. Values from which the radiation intensity was dependent could be controlled individually: the distance between measurer and source, as well as the voltage generating partial discharges. The obtained results indicate that in the examined phenomenon, significant dose of X-ray radiation is present. According to the Kramers-Kulenkampff theory, it depends also on the atomic number of elements involved. Using MATLAB software, the obtained data were compiled to develop suitable theory for further research study. There was also implemented fuzzification for the fuzzy logic, and the effect was the capability of forecasting radiation doses according to the fixed variables for a given material, where partial discharges were generated.
11
Content available remote

The Critical Evaluation of the Vibroacoustic Criteria Used in Poland to Diagnose of Power Transformer Cores

81%
Borucki S., Cichon A., Boczar T., Zmarzly D.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
391-394
EN
The subject matter of this article concerns the diagnostic test results of transformer cores by measuring and analysing vibroacoustic signals registered during their normal operation. The main objective of this research study conducted by the authors, the results of which are published in this paper, is a critical analysis of vibroacoustic criteria, which are adopted in Poland nowadays, and based on which, the assessment of the core technical condition is performed. This article presents exemplary results that were obtained on two twin units of type TET 8509 with a power of 40 MVA. The paper specifies diagnosed structures, the measurement system applied, and the currently used methodology to assess the degree of core loosening. To determine the efficacy and assessment accuracy of the applied vibroacoustic criteria, correlation between mechanical vibration measurements of the tested transformer tanks and results obtained by gas chromatography was performed.
12
Content available remote

Analysis of Optical Radiation Generated by Partial Discharges on Insulators

81%
Frącz P., Boczar T., Borucki S.
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vol. 125
|
issue 6
1360-1367
EN
Results of measurements of optical radiation emitted by partial and complete electrical discharges occurring on a bushing insulator model placed in air are presented in the article. Registration was performed using a spectrophotometer, enabling for measurement of optical radiation in the range from 270 to 1700 nm. Detailed characteristics of spectrophotometer are presented in our previous paper. The primary objective of the laboratory tests was to evaluate the impact of supply voltage changes in the range from 0 to 0.99 U_{b} (breakdown voltage) on the intensity and spectral character of the optical radiation emitted by partial discharges generated on the porcelain insulation surface of the bushing insulator. In the scope of studies analyzes of the effects of voltage changes on the obtained spectral waveforms were performed, whereby voltage increase and reduction was examined separately. Additionally, measurements and analyzes carried out included impact estimation of the time period as the voltage was applied to the high-voltage electrodes on the course of optical phenomena related to the generation of partial discharges.
13
Content available remote

Analysis of Interference Signals Generated by Vibroacoustic Vibrations of Transformer Cores

81%
Boczar T., Borucki S., Cichoń A.
|
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vol. 125
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issue 6
1355-1359
EN
The article deals with the subject matter referring to the interference that may accompany measurements of vibroacoustic signals, generated by electric power transformers, taken by using the acoustic emission method under industrial conditions. Paper concerns measurement and analysis of internal, acoustic type disturbances, including the magnetostrictive vibrations of plate sets within the transformer core, caused by changes in the magnetic flux. Paper presents measurement results of acoustic interfering signals and results of analyses made in the frequency and time-frequency domains. Power spectral density, MUSIC pseudospectra, two- and three-dimensional short time Fourier transform spectrograms, continuous wavelet transform scalograms, discrete wavelet transform, and quantities of energy transferred are included in the paper.
14
Content available remote

Numerical Simulation of Acoustic Wave Propagating in a Spherical Object Filled with Insulating Oil

81%
Wotzka D., Zmarzły D., Boczar T.
|
|
issue 6
1272-1275
EN
Results of a numerical simulation of an acoustic wave that propagates in a spherical object filled with insulating oil are presented in the paper. The sinusoidal acoustic wave is generated by an electro-acoustic transducer mounted in the middle of the object. Presented results depict acoustic pressure distribution within the transient and the steady states in a two-dimensional object. Furthermore, comparison of short time simulations adapting different mesh element size is presented.
15
Content available remote

Repeatability Estimation for Vibration Measurement Results of Power Transformer Core

81%
Borucki S., Cichon A., Skubis J., Boczar T.
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vol. 125
|
issue 6
1299-1302
EN
The subject matter of this paper refers to the diagnostics of a transformer core, based on measurements and analysis of vibroacoustic signals registered during their normal operation. The paper presents results of the research aimed to evaluate the repeatability of vibration measurements for power transformer core. Recording of vibroacoustic signals was performed under laboratory conditions on dry-insulated transformers. The study concerned evaluation of changes in vibroacoustic indicators of the transformer core during operation with a turned and loosened core. Conclusions from the measurement results were drawn on the basis of the parametric test of significance derived from the variance analysis for many means of single classification basing on the Fisher-Snedecor F-distribution.
16
Content available remote

Frequency and Time-Frequency Analysis of Acoustic Cavitation Noise in Insulating Oils

81%
Szmechta M., Boczar T., Frącz P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
744-747
EN
The paper presents some observations of ultrasound induced cavitation phenomenon in a mineral insulating oil. The acoustic cavitation phenomenon was generated at different signal frequencies and rms voltage value supplied to round piezoelectric transducers. Used transducers have created a high energy acoustic field in prepared insulating oil samples. The acoustic emission signal contains a broad-band noise and a fundamental frequency component and its harmonics, produced by the direct driving acoustic field. The paper presents the spectral analysis of acoustic emission signal observed during acoustic cavitation in insulating oils. To emphasize the changes in acoustic cavitation intensity also time-frequency analysis was used and some spectrograms were evaluated. The measurement uncertainty of some frequency-rms voltage pairs was very unfavorable. The main application expected with created cavitation measurement system is to develop a diagnostic tool for the aging of oil, based on the hypothesis that the measured cavitation intensity and spectrum could be affected by aging. Previous published measurements showed some relationship between insulating oil aging process and changes of acoustic emission of cavitations.
17
Content available remote

Mathematical Model and Numerical Analysis of~AE Wave Generated by Partial Discharges

81%
Wotzka D., Boczar T., Fracz P.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
767-771
EN
Paper presents definition of a mathematical model describing acoustic emission signals generated by partial discharges occurring in oil immersed electric power transformers. Time runs, power spectral density graphs and spectrograms of acoustic emission signals generated in experiments, performed under laboratory conditions, and of equivalent signals, calculated on the basis of the mathematical model, are presented. Furthermore, results of numerical simulations of acoustic pressure distribution inside a tank filled with insulation oil are presented in the paper. In the center of the tank acoustic emission wave sources were placed, each generating signals described by the model developed.
18
Content available remote

Analysis of Vibro-Acoustic Signals Generated during Operation of Micro Wind Turbines

81%
Wotzka D., Boczar T., Malec T., Pierzga R.
Acta Physica Polonica A
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2013
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vol. 124
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issue 3
595-597
EN
Results of a measurement and analysis of vibro-acoustic signals generated by two low power vertical-axis wind turbines that are installed on the roof of the Electric Power Institute at Opole University of Technology are presented in the paper. The study considers a Darrieus and a Savonius type wind turbines of rated power 1 kW each. For registration of the vibrations of the turbine mast three uniaxial accelerometers and a measurement equipment from Brüel & Kjær were applied. The measurement setup is presented in the paper. A comparative analysis of the registered data in the time and time-frequency domains was performed. Results depict changes in the recorded signals in time and frequency under different meteorological conditions, i.e. for different wind speed values. Based on the achieved results significant differences in the mast vibrations of the two kinds of wind turbines were stated.
19
Content available remote

Acoustic Spectra of Ultrasound Induced Cavitations in Insulating Oils

81%
Szmechta M., Zmarzły D., Boczar T., Lorenc M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6A
A-231-A-238
EN
Acoustic emission measurement results of acoustically induced cavitation bubbles in insulating oil are presented in this paper. Spectral analysis of acquired by a broadband transducer acoustic emission signals is proposed as a diagnostic tool for estimation of aging properties of mineral insulating oils. The article describes the main parts of the designed and built measurement apparatus used for acoustic cavitation investigation in insulating oils. In this note representative results of the experimental data taken from the apparatus are shown.
20
Content available remote

Analysis of Optical Radiation Generated by Electrical Discharges on Support Insulator

81%
Frącz P., Boczar T., Zmarzły D., Szczyrba T.
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EN
Subject of the paper concerns determination of the feasibility and indication of the application scope of optical spectroscopy methods in the diagnosis of high-voltage insulators. Results of measurements of optical radiation emitted by partial and complete electrical discharges occurring on a support insulator model placed in air are presented in the paper. Registration was performed using a spectrophotometer, enabling for measurement of optical radiation in the range from 200 to 1800 nm. The primary objective of the laboratory tests was to evaluate the impact of supply voltage changes in the range from 0 to 60 kV on the intensity and spectral character of the optical radiation emitted by electric discharges generated on the porcelain insulation surface of the support insulator. In the scope of studies analyzes of the effects of voltage changes on the obtained spectral wave forms were performed, whereby voltage increase and reduction was examined separately. Additionally, measurements and analyzes carried out included impact estimation of the time period as the voltage was applied to the high-voltage electrodes on the course of optical phenomena related to the generation of electrical discharges.
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