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

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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Calibration and Laboratory Testing of Computer Measuring System 8AE-PD Dedicated for Analysis of Acoustic Emission Signals Generated by Partial Discharges Within Oil Power Transformers

Archives of Acoustics ◽

10.1515/aoa-2017-0032 ◽

2017 ◽

Vol 42 (2) ◽

pp. 297-311 ◽

Cited By ~ 2

Author(s):

Franciszek Witos ◽

Grzegorz Szerszeń ◽

Zbigniew Opilski ◽

Maciej Setkiewicz ◽

Aneta Olszewska ◽

...

Keyword(s):

Acoustic Emission ◽

Steel Plate ◽

Partial Discharges ◽

Measuring System ◽

Power Transformers ◽

General Description ◽

Emission Method ◽

Peak Voltage ◽

Limit Values ◽

Ae Signals

Abstract In the paper, there are presented a general description of the constructed measuring system 8AE-PD, the results of calibration of this system by the Hsu-Nielsen method as well as the testing of the measuring system during recording signals generated by Hsu-Nielsen sources in a steel plate and a modeled partial discharge (PD) source. There is also presented the methodology of investigations by the calibrated acoustic emission method. The results of analyses of PD signals coming from the modeled sources are given. In particular, there are described the properties of acoustic emission (AE) signals generated by the PDs as well as the dependencies of the peak-to-peak voltage Umm, the RMS voltage Urms and the descriptors of acronyms ADP and ADC on the apparent charge Q introduced by the modeled PD source. There are determined the limit values of the apparent charge Q introduced by the modeled PD source for which the recorded signal is identified as originating from the PDS.

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

Archives of Acoustics ◽

10.1515/aoa-2016-0077 ◽

2016 ◽

Vol 41 (4) ◽

pp. 799-812 ◽

Cited By ~ 4

Author(s):

Aneta Olszewska ◽

Franciszek Witos

Keyword(s):

Power Transformer ◽

Partial Discharges ◽

Time Frequency ◽

The Core ◽

Frequency Domains ◽

Extended Frequency Range ◽

Extended Frequency ◽

Side Walls ◽

Ae Signals

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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A strategy to locate partial discharges in power transformers using acoustic emission

Renewable Energy and Power Quality Journal ◽

10.24084/repqj05.344 ◽

2007 ◽

Vol 1 (05) ◽

pp. 596-600 ◽

Cited By ~ 1

Author(s):

Giscard Franceire Cintra Veloso ◽

◽

Luiz Eduardo Borges da Silva ◽

Germano Lambert-Torres

Keyword(s):

Acoustic Emission ◽

Partial Discharges ◽

Power Transformers

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The influence of ultrasound signal parameters on sonoluminescence light intensity

Archives of Electrical Engineering ◽

10.2478/aee-2013-0048 ◽

2013 ◽

Vol 62 (4) ◽

pp. 605-612

Author(s):

Marek Szmechta ◽

Tomasz Boczar ◽

Dariusz Zmarzły

Keyword(s):

Acoustic Emission ◽

Acoustic Waves ◽

Power Transformer ◽

Electrical Power ◽

Partial Discharges ◽

Research Project ◽

Insulation Systems ◽

Secondary Phenomenon ◽

New Research ◽

The Relationship

Abstract Topics of this article concern the study of the fundamental nature of the sonoluminescence phenomenon occurring in liquids. At the Institute of Electrical Power Engineering at Opole University of Technology the interest in that phenomenon known as secondary phenomenon of cavitation caused by ultrasound became the genesis of a research project concerning acoustic cavitation in mineral insulation oils in which a number of additional experiments performed in the laboratory aimed to determine the influence of a number of acoustic parameters on the process of the studied phenomenona. The main purpose of scientific research subject undertaken was to determine the relationship between the generation of partial discharges in high-voltage power transformer insulation systems, the issue of gas bubbles in transformer oils and the generated acoustic emission signals. It should be noted that currently in the standard approach, the phenomenon of generation of acoustic waves accompanying the occurrence of partial discharges is generally treated as a secondary phenomenon, but it can also be a source of many other related phenomena. Based on our review of the literature data on those referred subjects taken, it must be noted, that this problem has not been clearly resolved, and the description of the relationship between these phenomena is still an open question. This study doesn’t prove all in line with the objective of the study, but can be an inspiration for new research project in the future in this topic. Solution of this problem could be a step forward in the diagnostics of insulation systems for electrical power devices based on non-invasive acoustic emission method.

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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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Otkrivanje i analiza signala parcijalnih pražnjenja u energetskom transformatoru UHF metodom

Energija, Ekonomija, Ekologija ◽

10.46793/eee20-1-2.096d ◽

2020 ◽

Vol 22 (1-2) ◽

pp. 96-101

Author(s):

Đorđe Dukanac ◽

Keyword(s):

Detailed Analysis ◽

Background Noise ◽

Power Transformer ◽

Partial Discharge ◽

Spectral Composition ◽

Partial Discharges ◽

Power Transformers ◽

Discharge Source ◽

Useful Components

This paper presents the practical detection of partial discharge signals using a UHF sensor mounted on a power transformer and then the detailed analysis of a signal is done. The first part of the paper describes possible partial discharge sources in power transformers, UHF method and UHF sensor. In the second part of the paper, received signal at UHF sensor is considered. In order to accurately determine the magnitude of the partial discharge signal, especially if the location of the partial discharge source is far from the location of the UHF sensor, it is necessary to separate the signal from the background noise. This is only possible at intervals between individual bursts of the observed partial discharges. The spectral composition of the received signal is considered and a method for separating the present noise from the useful components of the partial discharge signal is established. The presumable main cause of partial discharges is evaluated.

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ACOUSTIC EMISSION TESTING OF POWER TRANSFORMERS INSULATION

Kontrol Diagnostika ◽

10.14489/td.2020.06.pp.040-044 ◽

2020 ◽

pp. 40-44

Author(s):

V. V. Bardakov ◽

S. V. Elizarov ◽

V. A. Barat ◽

V. G. Kharebov ◽

K. A. Medvedev

Keyword(s):

Acoustic Emission ◽

High Sensitivity ◽

Partial Discharges ◽

Power Transformers ◽

Acoustic Emission Method ◽

Emission Method ◽

Emission Data ◽

Emission Testing ◽

Insulation Defect ◽

Acoustic Emission Testing

Testing results of power transformers insulation for the presence of insulation defects, accompanied by the partial discharges occurrence, by means of the acoustic emission method are presented in this article. In particular, the testing of two power transformers with different lifetime was carried out. One transformer was defect-free and one with a willing insulation defect. Based on the testing results, the features of acoustic emission data for power transformers in the presence of partial discharges are found. High sensitivity of acoustic emission method for acoustic wave registration from partial discharges is shown in the article. A method for filtering of noise hits and extraction of hits from partial discharges is proposed. This method is based on excretion of acoustic emission hits from partial discharges out of total number of hits by means of periodicity of their registration, which is synchronized with power supply frequency on the first step. On the next step based on acoustic emission parameters of hits excretion on the previous step, filtration was carried out. The location of the insulation defect which led to the appearance of partial discharges was determined based on the volume location algorithm, by means of acoustic emission method. The insulation defect was confirmed by verification.

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Development of Acoustic Emission Sensor Optimized for Partial Discharge Monitoring in Power Transformers

Sensors ◽

10.3390/s19081865 ◽

2019 ◽

Vol 19 (8) ◽

pp. 1865 ◽

Cited By ~ 13

Author(s):

Sikorski

Keyword(s):

Acoustic Emission ◽

Partial Discharge ◽

Low Noise ◽

Partial Discharges ◽

Power Transformers ◽

Laboratory Research ◽

Fully Differential ◽

Peak Sensitivity ◽

Optimal Material ◽

Discharge Detection

The acoustic emission (AE) technique is one of the unconventional methods of partial discharges (PD) detection. It plays a particularly important role in oil-filled power transformers diagnostics because it enables the detection and online monitoring of PDs as well as localization of their sources. The performance of this technique highly depends on measurement system configuration but mostly on the type of applied AE sensor. The paper presents, in detail, the design and manufacturing stages of an ultrasensitive AE sensor optimized for partial discharge detection in power transformers. The design assumptions were formulated based on extensive laboratory research, which allowed for the identification of dominant acoustic frequencies emitted by partial discharges in oil–paper insulation. The Krimholtz–Leedom–Matthaei (KLM) model was used to iteratively find optimal material and geometric properties of the main structures of the prototype AE sensor. It has two sensing elements with opposite polarization direction and different heights. The fully differential design allowed to obtain the desired properties of the transducer, i.e., a two-resonant (68 kHz and 90 kHz) and wide (30‒100 kHz) frequency response curve, high peak sensitivity (−61.1 dB ref. V/µbar), and low noise. The laboratory tests confirmed that the prototype transducer is characterized by ultrahigh sensitivity of partial discharge detection. Compared to commonly used commercial AE sensors, the average amplitude of PD pulses registered with the prototype sensor was a minimum of 5.2 dB higher, and a maximum of 19.8 dB higher.

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