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The article describes the non-contact and contact analysis of 1-MVA dry power transformers with epoxy-resin insulation using an acoustic camera and frequency analyzer with automatic sweeping for low-middle frequency areas. Power transformers are most commonly used for construction component (core, windings, taps) analysis. The electrical, non-rotating machine generates electromagnetic and acoustic emissions that can be used to analyze dry transformers during their operation. Non-contact online diagnostic methods have many advantages over offline methods because it is not necessary to shut down the transformer, and also, the condition and behaviour of the machine are analyzed during its normal operation. The article presents the analysis and comparison of structural parts of the distribution dry transformers of the same type and power. The problem of insufficient or incorrect clamp-screw connection was identified using the SFRA (Sweep Frequency Response Analysis) method.

The paper presents experimental diagnostics of the oil-paper insulating system of power transformers using progressive frequency method. The first part of the paper deals with the basic information about diagnostics of power oil transformers. The second part of the paper deals with the use of frequency domain spectroscopy (FDS) for power oil transformers. This method is used in the analysis of insulating condition of power transformer with the system of oil-paper. It was found that the results of these tests are highly influenced by the operating temperature during the experimental measurement. Moisture and conductivity between the insulating transformer paper and oil in an insulating system are highly dependent on the temperature. In the other part, the paper presents experimental results of the diagnostic measurement for a real traction oil transformer at different operating temperatures and states (with oil and without). Finally, the paper presents comparative measurement among several autotransformers with the same power. In experimental measurements, the correlation between the measured values and the operational aspects of the individual oil autotransformers are shown.

The article presents a theoretical analysis of electromagnetic compatibility (EMC) and experimental measurement of effects of radiation and acoustic emission of high-voltage transformers for electronic equipment and working personnel in a control room. Electromagnetic compatibility and safety of equipment are not considered as two distinct areas of study in electric and electronic safety. Economic criteria cannot compromise safety but at the same time immunity levels must be relevant in order to establish a “Functional Safety”. Introducing Special Immunity Levels in the level of equipment testing allows us to combine the two areas of EMC and safety. The measurement was carried out in high-current of very high-voltage distribution station. A real-life analysis of effects of electric and electromagnetic field was carried out. FFT was used for mathematical processing of data which were later presented in a graphical form of a spectrally analyzed area. In the last part of the paper we discuss the suitability of acoustic camera to perform contactless monitoring of the health and operation conditions of the power transformer by analyzing acoustic field generated by the transformer core and windings in near control room.

The authors describe experimental and theoretical analyses of faults of power transformer winding. Faults were caused by mechanical effect of short-circuit currents. Measurements of transformer were carried out in high-voltage laboratory. Frequency and time diagnostic methods (method SFRA - Sweep Frequency Response Analysis, impact test) were used for the analyses. Coils of transformer windings were diagnosed by means of the SFRA method and the time impact test. The analyzed methods had a significant sensitivity to a relatively small deformation of coil. In the analysis a new technique for analyzing the effects of short-circuit currents is introduced. This technique is developed for high-voltage transformers (different types of power). The proposed analyses show that it is necessary to analyze the value of short-circuit current. Short-circuit current represents a danger for the operation of the power transformer. The proposed approach can be used for other types of transformers. Moreover, the presented techniques have a potential application for fault diagnosis of electrical equipment such as: transformers and electrical machines.

Fault diagnosis techniques of electrical motors can prevent unplanned downtime and loss of money, production, and health. Various parts of the induction motor can be diagnosed: rotor, stator, rolling bearings, fan, insulation damage, and shaft. Acoustic analysis is non-invasive. Acoustic sensors are low-cost. Changes in the acoustic signal are often observed for faults in induction motors. In this paper, the authors present a fault diagnosis technique for three-phase induction motors (TPIM) using acoustic analysis. The authors analyzed acoustic signals for three conditions of the TPIM: healthy TPIM, TPIM with two broken bars, and TPIM with a faulty ring of the squirrel cage. Acoustic analysis was performed using fast Fourier transform (FFT), a new feature extraction method called MoD-7 (maxima of differences between the conditions), and deep neural networks: GoogLeNet, and ResNet-50. The results of the analysis of acoustic signals were equal to 100% for the three analyzed conditions. The proposed technique is excellent for acoustic signals. The described technique can be used for electric motor fault diagnosis applications. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Solving the problems of increasing requirements on transport, while respecting actual environment criteria, new solutions are being looked for to make an optimum mutual equilibrium. One of the possibilities of increasing ecological conditions, which are decreased by means of transporting a mine, shows this contribution that suggests a reconstruction of the original diesel-hydraulic engine DH30 to twosystem drive and hybrid drive. In the reconstruction, a DC and an asynchronous engine are suggested as traction engines. This reconstruction of the drive means not only increase of the ecological conditions in the mine but also an ability to use biofuel made from a crop that grew on contaminated soil. The aim of the reconstruction is to replace the combustion engine and hydraulic distribution with an electric drive while traction characteristics will remain at their values. A one-engine traction drive with an asynchronous engine with short circuit armature is regarded as one of the most prospective for an output range from several W up to MW. By using the asynchronous engine powered from semiconductive changer the problem of pulsing parts of torque is dealt with regulation. This reconstruction also means energy saving. This system also improves storing and manipulation with oil production in the mine. [ABSTRACT FROM AUTHOR]