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1
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The Application of the Selected Time-Frequency Descriptors Detection of the Acoustic Emission Signals Generated by Multisource Partial Discharges

100%
Cichon A.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 3
290-293
EN
The paper presents the comparative analysis results of the acoustic emission signals generated by various forms of partial discharges occurring in multisource systems. Modern methods of the signal digital processing: a short-time Fourier transform and continuous and discrete wavelet transforms were applied for the assessment of the results in the time-frequency domain. The acoustic emission signals generated by partial discharges were registered with a WD AH17 contact transducer by the Physical Acoustics Corporation placed on the external part of the tub.
2

Nitrogen removal from wastewater with high ammonia nitrogen comcentration via shorter nitrification and denitrification

51%
Surmacz-Gorska J., Cichon A., Miksch A.
Biotechnologia
|
1997
|
issue 1
52-58
EN
Research carried out confirmed the possibility removal by means of shorter nitrification and denitrification in high ammonia concentration wastewater.During nitrification ammonia nitrogen was oxidized to nitrite nitrogen and further oxidation to nitrate nitrogen was stopped.Build-up of nitrite nitrogen was reduced to free nitrogen during denitrification process where reduction of nitrate nitrogen to nitrite nitrogen was avoided.
3
Content available remote

Diagnostics of the Core Mechanical Construction Based on Vibroacoustic Measurements and Distribution of Temperature Field in Transformer Magnetic Circuit

51%
Borucki S., Cichon A., Boczar T.
Acta Physica Polonica A
|
2015
|
vol. 128
|
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%.
4
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The Critical Evaluation of the Vibroacoustic Criteria Used in Poland to Diagnose of Power Transformer Cores

51%
Borucki S., Cichon A., Boczar T., Zmarzly D.
Acta Physica Polonica A
|
2013
|
vol. 124
|
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.
5
Content available remote

Characteristic of Acoustic Signals Generated by Operation of On Load Tap Changers

51%
Cichon A., Fracz P., Zmarzly D.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 4
585-588
EN
Possibilities of application of the acoustic method for the on load tab changers diagnosis has been presented in the paper. The analysis of measurement results gathered during research works performed under laboratory conditions has been presented in detail. The registered acoustic signals have been analyzed in time and time-frequency domains. The time domain analysis has been performed by presentation of time runs and their envelopes determined by use of the Hilbert transform. Evaluation of the time-frequency components has been performed by use of the short-time Fourier transform, the discrete and the continuous wavelet transforms.
6
Content available remote

Repeatability Estimation for Vibration Measurement Results of Power Transformer Core

51%
Borucki S., Cichon A., Skubis J., Boczar T.
|
|
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.
7
Content available remote

The Wavelet Analysis of the Vibroacoustic Signal Measurement in a Transient State Operation of Power Transformer

51%
Borucki S., Cichon A., Boczar T., Zmarzly D.
Acta Physica Polonica A
|
2012
|
vol. 122
|
issue 5
800-803
EN
The article presents the results of attempts made to develop a non-invasive diagnostic method of a technical state of a transformer's core based on an analysis of mechanical vibrations registered during the start-up of the transformer analyzed. The paper presents a characteristic of the transformer under study, the measuring systems applied and the method developed for assessing the degree of the core loosening. The original results presented in the paper have been obtained under laboratory conditions during tests conducted on an oil transformer of 200 kVA. The analysis of recorded virboacoustic signals was performed by means of discrete wavelet transform for three different operating cases: the transformer with no core defect, the transformer with loose screws of the magnetic circuit of the upper yoke, and the transformer with completely loosen screws of the beam of the upper yoke and the lower core. The signals have been recorded on two perpendicular measuring axes: 0X and 0Y and their measured values were subject to the wavelet analysis.
8
Content available remote

The Analysis of Mechanical Vibrations and Acoustic Pressure Level οf a Transformer Model

51%
Boczar T., Borucki S., Cichon A., Lorenc M.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 6A
A-21-A-26
EN
The paper presents the results of vibroacoustic investigations and the measurements of the acoustic pressure level (noise) of a transformer model. The measurements were taken at a full transformer load in two operation conditions: at a producer packeted core and at unpacketed core. Unpacketing consisted in loosing the screws pressing the particular core plates. Mechanical vibrations were registered and the acoustic pressure level was measured. The vibroacoustic analysis results are presented in the form of frequency spectra and the results of the acoustic analysis of the transformer under study are shown by determining corrected values of the acoustic pressure level and by a frequency analysis.
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