Identification of Acoustic Emission Signals Originating from the Core Magnetization of Power Oil Transformer

Abstract In this paper, the properties of AE signals originating from phenomena occurring during magnetization of ferromagnetic materials which are used to construct power transformer cores are presented. The AE signals in a selected power oil transformer were recorded and analyzed. The analysis included, i.e., time, frequency, and time-frequency analyses, calculations of amplitude distributions of the signals and defined AE descriptors, determination of the descriptor map on the side walls of transformers, as well as a detailed analysis of selected part of the signals. The maps of descriptors were analyzed in the frequency bands of 20–70 kHz, 70–100 kHz, and 100–200 kHz. The analysis of the properties of the signals was performed in time and frequency domains. Based on the analysis, there were identified the AE signals originating from the phenomena occurring during the core magnetization of a power oil transformer. To identify those phenomena, the maps of the ADC descriptor calculated in the band of 20–70 kHz when selecting the measurement points in which there were no AE sources from partial discharges were used. An analysis of magnetoacoustic emission signals in the bands of 70–100 kHz and 100–200 kHz was also performed. The analysis of the signal properties in such an extended frequency range allowed determining the properties of the magnetoacoustic signals coming from core sheets of power oil transformers.

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Application of Acoustic Emission and Thermal Imaging to Test Oil Power Transformers

Energies ◽

10.3390/en13225955 ◽

2020 ◽

Vol 13 (22) ◽

pp. 5955

Author(s):

Franciszek Witos ◽

Aneta Olszewska ◽

Zbigniew Opilski ◽

Agnieszka Lisowska-Lis ◽

Grzegorz Szerszeń

Keyword(s):

Acoustic Emission ◽

Thermal Imaging ◽

Research Method ◽

Power Transformer ◽

Partial Discharges ◽

Power Transformers ◽

Imaging Studies ◽

Ir Radiation ◽

Side Walls ◽

Ae Signals

In this paper, the research methodology and the results of the analysis carried out using the acoustic emission (AE) and thermal imaging for a selected oil power transformer are presented. The basis for the research, by means of the AE method, was the author’s patented research method. The AE descriptor maps on the side walls of the tested transformer along with the location of areas with increased AE activity and an analysis of the properties of AE signals recorded at the measurement points located in these areas have been performed. The results showed no partial discharges that could threaten further operation of the tested transformer as well as three areas where increased magnetoacoustic emission occurred. Thermal imaging studies were carried out in the 7.5 μm < λ < 13 μm band. Three areas were located on the calculated thermograms: the entire upper surface of the transformer tank and two areas on the side walls of the tested transformer in which increased IR radiation occurred. The results of the analysis of the research results for the two methods correspond with each other, having a common part, and complement each other giving a broader description of studied phenomena.

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Fault Detection of a Spherical Tank Using a Genetic Algorithm-Based Hybrid Feature Pool and k-Nearest Neighbor Algorithm

Energies ◽

10.3390/en12060991 ◽

2019 ◽

Vol 12 (6) ◽

pp. 991 ◽

Cited By ~ 11

Author(s):

Md Hasan ◽

Jong-Myon Kim

Keyword(s):

Fault Detection ◽

Nearest Neighbor ◽

K Nearest Neighbor ◽

Time Frequency ◽

Reduction Techniques ◽

Spherical Tank ◽

Frequency Domains ◽

Dimensionality Reduction Techniques ◽

Linear Dimensionality Reduction ◽

Ae Signals

Fault detection in metallic structures requires a detailed and discriminative feature pool creation mechanism to develop an effective condition monitoring system. Traditional fault detection methods incorporate handcrafted features either from the time, frequency or time-frequency domains. To explore the salient information provided by the acoustic emission (AE) signals, a hybrid of feature pool creation and an optimal features subset selection mechanism is proposed for crack detection in a spherical tank. The optimal hybrid feature pool creation process is composed of two major parts: (1) extraction of statistical features from time and frequency domains, as well as extraction of traditional features associated with the AE signals; and (2) genetic algorithm (GA)-based optimal features subset selection. The optimal features subset is then provided to the k-nearest neighbor (k-NN) classifier to distinguish between normal (NC) and crack conditions (CC). Experimental results show that the proposed approach yields an average 99.8% accuracy for heath state classification. To validate the effectiveness of the proposed approach, it is compared to conventional non-linear dimensionality reduction techniques, as well as those without feature selection schemes. Experimental results show that the proposed approach outperforms conventional non-linear dimensionality reduction techniques, achieving at least 2.55% higher classification accuracy.

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Phase insensitive ultrasonic attenuation coefficient determination of fresh bovine liver over an extended frequency range

Medical Physics ◽

10.1118/1.595030 ◽

1981 ◽

Vol 8 (5) ◽

pp. 692-694 ◽

Cited By ~ 41

Author(s):

J. D. Pohlhammer ◽

C. A. Edwards ◽

W. D. O'Brien

Keyword(s):

Attenuation Coefficient ◽

Ultrasonic Attenuation ◽

Bovine Liver ◽

Frequency Range ◽

Extended Frequency Range ◽

Extended Frequency

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Simulation of Real-Time Frequency Estimators for Pulsed Doppler Systems

Ultrasonic Imaging ◽

10.1177/016173468600800403 ◽

1986 ◽

Vol 8 (4) ◽

pp. 252-271 ◽

Cited By ~ 37

Author(s):

G.H. van Leeuwen ◽

A.P.G. Hoeks ◽

R.S. Reneman

Keyword(s):

Real Time ◽

Instantaneous Frequency ◽

Wide Frequency Range ◽

Frequency Range ◽

Zero Crossings ◽

Time Frequency ◽

Doppler Signals ◽

Extended Frequency Range ◽

Extended Frequency ◽

Frequency Detector

Four time-domain oriented, real-time frequency estimators, based on the detection of phase, zero-crossings, instantaneous frequency or autocorrelation, were simulated on a digital computer and subjected to computer generated Doppler signals, enabling the investigation of the influence of spectral shape, filtering, frequency shift, noise and quantization. Three estimators, the autocorrelator as well as the instantaneous frequency detector and the autocorrelator, both with extended frequency range, appeared to be very accurate. They exhibit a bias in the estimator output of less than 2 percent over a wide frequency range, the former up to nearly the Nyquist frequency, the latter two beyond, even for skew spectra and under poor signal conditions regarding bandwidth and noise.

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The determination of electrode impedances over an extended frequency range by ac-bridge methods

Electrochimica Acta ◽

10.1016/0013-4686(68)80023-4 ◽

1968 ◽

Vol 13 (2) ◽

pp. 215-239 ◽

Cited By ~ 49

Author(s):

R.D. Armstrong ◽

W.P. Race ◽

H.R. Thirsk

Keyword(s):

Frequency Range ◽

Extended Frequency Range ◽

Extended Frequency

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Study on Descriptors of Acoustic Emission Signals Generated by Partial Discharges under Laboratory Conditions and in On-Site Electrical Power Transformer

Archives of Acoustics ◽

10.1515/aoa-2016-0026 ◽

2016 ◽

Vol 41 (2) ◽

pp. 265-276 ◽

Cited By ~ 19

Author(s):

Michał Kunicki ◽

Andrzej Cichoń ◽

Sebastian Borucki

Keyword(s):

Acoustic Emission ◽

Power Transformer ◽

Electrical Power ◽

High Sensitivity ◽

Laboratory Research ◽

Time Frequency ◽

Laboratory Conditions ◽

Set Up ◽

Point To Point ◽

Ae Signals

Abstract An acoustic emission method (AE) is widespread and often applied for partial discharge (PD) diagnostics, mainly due to its ease of application as well as noninvasiveness and relatively high sensitivity. This paper presents comparative analysis of AE signals measurement results archived under laboratory conditions as well as on-site actual AE signals generated by inside PDs in electrical power transformer during its normal service. Three different PD model sources are applied for laboratory research: point to point, multipoint to plate and surface type. A typical measuring set up commonly used for on-site transformer PD diagnostics is provided for the laboratory tasks: piezoelectric joint transducer, preamplifier, amplifier and measuring PC interface. During the on-site research there are three measuring tracks applied simultaneously. Time domain, time-frequency domain and statistical tools are used for registered AE signals analysis. A number of descriptors are proposed as a result of the analysis. In the paper, at- tempt of AE signals descriptors, archived under laboratory condition application possibilities for on-site PD diagnostics of power transformers during normal service is made.

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Feasibility of studying 460 MPa high-strength steel affected by strain aging with acoustic emission method

Advances in Structural Engineering ◽

10.1177/1369433220950615 ◽

2020 ◽

pp. 136943322095061

Author(s):

Yiting Yang ◽

Yan Wang ◽

Kehao Li

Keyword(s):

Acoustic Emission ◽

High Strength Steel ◽

Strain Aging ◽

High Strength ◽

Tensile Tests ◽

Aging Effects ◽

Time Frequency ◽

Frequency Domains ◽

Ae Signals ◽

Partial Damage

Strain aging significantly influences the behavior of partially damaged structural steel. The effects of strain aging can be determined based on mechanical experiments, but the sampling process causes further damage to the structures. To explore the possibility of using nondestructive testing (NDT) technology to distinguish the strain aging effects on steel materials, this study investigates the characteristics of acoustic emission (AE) signals for high-strength steel (HSS) affected by strain aging. First, different strain aging effects were applied to 460 MPa HSS specimens. Second, pencil lead break (PLB) tests were performed on the specimens with strain aging, and the generated AE signals were recorded. Finally, tensile tests were conducted, that the strain aging effects on mechanical behavior were determined. The obtained AE signals were compared by extracting the AE parameters and analyzed in the frequency and time-frequency domains with a fast Fourier transform (FFT) and a wavelet transform (WT), respectively. The study shows that the strain aging effects change the characteristics of the AE signals. Compared to the prestrain, the aging time has a more pronounced impact on the AE behaviors. This research proposes a possible NDT method to determine the effects of strain aging on steel materials. Experimental data are provided to detect the degree of partial damage to 460 MPa HSS owing to strain aging using the AE method.

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Imaging of ribosomal RNA-protein interactions by dark-field STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153221 ◽

1989 ◽

Vol 47 ◽

pp. 250-251

Author(s):

M. Boublik ◽

V. Mandiyan ◽

S. Tumminia ◽

J.F. Hainfeld ◽

J.S. Wall

Keyword(s):

Nucleic Acid ◽

16S Rrna ◽

Dark Field ◽

Radius Of Gyration ◽

Central Domain ◽

The Core ◽

16S Rna ◽

30S Subunit ◽

Core Particles

Success in protein-free deposition of native nucleic acid molecules from solutions of selected ionic conditions prompted attempts for high resolution imaging of nucleic acid interactions with proteins, not attainable by conventional EM. Since the nucleic acid molecules can be visualized in the dark-field STEM mode without contrasting by heavy atoms, the established linearity between scattering cross-section and molecular weight can be applied to the determination of their molecular mass (M) linear density (M/L), mass distribution and radius of gyration (RG). Determination of these parameters promotes electron microscopic imaging of biological macromolecules by STEM to a quantitative analytical level. This technique is applied to study the mechanism of 16S rRNA folding during the assembly process of the 30S ribosomal subunit of E. coli. The sequential addition of protein S4 which binds to the 5'end of the 16S rRNA and S8 and S15 which bind to the central domain of the molecule leads to a corresponding increase of mass and increased coiling of the 16S rRNA in the core particles. This increased compactness is evident from the decrease in RG values from 114Å to 91Å (in “ribosomal” buffer consisting of 10 mM Hepes pH 7.6, 60 mM KCl, 2 m Mg(OAc)2, 1 mM DTT). The binding of S20, S17 and S7 which interact with the 5'domain, the central domain and the 3'domain, respectively, continues the trend of mass increase. However, the RG values of the core particles exhibit a reverse trend, an increase to 108Å. In addition, the binding of S7 leads to the formation of a globular mass cluster with a diameter of about 115Å and a mass of ∽300 kDa. The rest of the mass, about 330 kDa, remains loosely coiled giving the particle a “medusa-like” appearance. These results provide direct evidence that 16S RNA undergoes significant structural reorganization during the 30S subunit assembly and show that its interactions with the six primary binding proteins are not sufficient for 16S rRNA coiling into particles resembling the native 30S subunit, contrary to what has been reported in the literature.

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The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

Izmeritel`naya Tekhnika ◽

10.32446/0368-1025it.2020-1-53-58 ◽

2020 ◽

pp. 53-58

Author(s):

A. V. Koudelny ◽

I. M. Malay ◽

V. A. Perepelkin ◽

I. P. Chirkov

Keyword(s):

Microwave Power ◽

Electromagnetic Waves ◽

Primary Standard ◽

The State ◽

Frequency Range ◽

Working Standard ◽

Extended Frequency Range ◽

Effective Efficiency ◽

Extended Frequency ◽

Good Agreement

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

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