The paper presents the application of the Cole-Cole model for determining the runs of the return voltage of the paper-oil insulation sample through a computer simulation. Different insulation conditions were simulated...
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The paper presents the application of the Cole-Cole model for determining the runs of the return voltage of the paper-oil insulation sample through a computer simulation. Different insulation conditions were simulated through an adequate selection of parameters alpha and tau of the Cole-Cole model. For calculation purposes, a series-parallel substitute scheme, obtained through approximation of a discrete characteristic operator impedance Z a of the model applied, was used. The diagnostics of the simulated insulation condition was based on the analysis of a few selected parameters of the return voltage, obtained from time characteristics.
With the wide spread of video usage in many fields of our lives, it becomes very important to develop new techniques for video denoising. Spatial video denoising using wavelet transform has been the focus of the curre...
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With the wide spread of video usage in many fields of our lives, it becomes very important to develop new techniques for video denoising. Spatial video denoising using wavelet transform has been the focus of the current researches as it requires less computation and more suitable for real-time applications. Two specific techniques for spatial video denoising using wavelet transform are considered in this work: 2D Discrete Wavelet Transform (2D DWT) and 2D Dual Tree Complex Wavelet Transform (2D DTCWT). Each of these techniques has its advantages and disadvantages. The first technique gives less quality at high levels of noise but consumes less time while the second gives high quality video while consuming long. In this work, we introduce an intelligent denoising system that makes a tradeoff between the quality of the denoised video and the time required for denoising. The system first estimates the noise level in the video frame then accordingly chooses the proper of the two denoising techniques to apply on the frame. The simulation results show that the proposed system is more suitable for real-time applications where the time is critical while giving high quality videos especially at low to moderate levels of noise.
E-learning has introduced new opportunities in teaching and learning electrical engineering subjects. This paper presents the architecture of a virtual engineering laboratory, designed to allow remote training in the ...
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E-learning has introduced new opportunities in teaching and learning electrical engineering subjects. This paper presents the architecture of a virtual engineering laboratory, designed to allow remote training in the control of DC, brushless DC, and stepper servomotors. An example of DC servomotors control on virtual laboratory is also presented.
The paper presents the measurement results of the noise level of a power transformer. The noise sources occurring in the transformer are presented, and the method applied and the measuring tools used are characterized...
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ISBN:
(纸本)9781627480000
The paper presents the measurement results of the noise level of a power transformer. The noise sources occurring in the transformer are presented, and the method applied and the measuring tools used are characterized. The measurements were taken in 29 points located around the transformer. The evaluation of noise was carried out based on the revised coefficient of the acoustic pressure level. The research work results presented enable the evaluation of the influence of the noise of the unit under study on its environment and make it easier to diagnose the degrees of wear of the fans installed in transformer coolers.
The paper will present the wavelet analysis results using continuous and discrete wavelet transforms of vibrations of a power transformer tub installed on the block of a conventional, thermal condensation power statio...
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ISBN:
(纸本)9781627480000
The paper will present the wavelet analysis results using continuous and discrete wavelet transforms of vibrations of a power transformer tub installed on the block of a conventional, thermal condensation power station. The research tests were carried out during a regular transformer operation in industrial conditions. The measurements were taken from the point of view of the evaluation of the influence of the vibrations registered on the analysis results of the acoustic emission signals generated by partial discharges that can occur in paper-oil insulation systems of power transformers. Moreover, the analyses carried out were supplemented with the research results obtained in laboratory conditions during the measurements taken in the high-voltage testing station of high-voltage power appliances. The influence of the loosened screws fastening the lid of the transformer tub on the time-frequency analysis results obtained of the vibrations registered was investigated. Moreover, the range of the research work carried out referred to the evaluation of the influence of the changes of the pressure force of the metal plates forming the transformer core on the vibration measurement results were obtained. In summary, the evaluation of usefulness was presented and the range of the time-frequency analysis application possibilities, and especially wavelet transforms, in diagnostics of power transformers using the acoustic methods was characterized.
The subject matter of this paper refers to vibroacoustic measurements of high power transformers. The evaluation method of the transformer technical condition, based on the measurements of mechanical vibrations of its...
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ISBN:
(纸本)9781627480000
The subject matter of this paper refers to vibroacoustic measurements of high power transformers. The evaluation method of the transformer technical condition, based on the measurements of mechanical vibrations of its tub, is characterized. The elements of the measuring set-up, which were used during the registration of the signals coming from the core and winding vibrations of a given transformer unit, transferred by the tub, are presented. Based on the criterion values of the vibroacoustic parameters measured: root-mean-square value of the vibration acceleration and the vibration spectrum amplitude in the frequency range from 0 to 3000 Hz, the evaluation of the technical condition of the power appliance under study was carried out.
The paper presents research results of electrokinetic zeta potential that exists in the electrical double layer on the border of the solid and liquid phases. For zeta potential examination, samples in the colloid form...
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The paper presents research results of electrokinetic zeta potential that exists in the electrical double layer on the border of the solid and liquid phases. For zeta potential examination, samples in the colloid form were used, the continuous (dispersing) phase of which was constituted by dielectric liquid mixtures formed on the base of simple hydrocarbons (hexane, cyclohexane, toluene), and the solid (dispersed) phase was constituted by materials in a disintegrated form (aluminum, copper, steatite, Al-70). The measurements were taken with Zetasizer 2000 - by Malvern Instruments (UK). Volume density of charge qw on the border of the solid and liquid phases, responsible for generation of electrostatic charges, was determined based on the measured zeta potential and physicochemical properties of the liquids under study.
This paper presents an analysis how the pulses in the long three-conductor coupled lines with common screen interact mutually. The interaction of pulses appears in those places of the line, where there is a change in ...
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This paper presents an analysis how the pulses in the long three-conductor coupled lines with common screen interact mutually. The interaction of pulses appears in those places of the line, where there is a change in characteristic impedance causing a change in reflection coefficient for pulses moving along the line. An exemplary analysis is conducted for a homogenous lossless line both at its starting and terminal point. The results of the analysis are analytical expressions describing quantitative interactions of pulses. The expressions are verified numerically and experimentally involving measurements of the real-life line. The mutual interaction of pulses can be useful in location of faults in electric power lines by means of the pulses method.
In our paper we are proposing a complex model of the student (learner) in a virtual educational environment, supported by a multi-agent system. The whole system is centered on the student and it mainly takes into acco...
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In our paper we are proposing a complex model of the student (learner) in a virtual educational environment, supported by a multi-agent system. The whole system is centered on the student and it mainly takes into account Vygotsky's socio-cultural theory that states that social interaction plays a fundamental role in the development of cognition. The model is part of a larger project - DANTE - Socio-Cultural Models implemented through multi-agent architecture for e-learning - that has as main objective the development of a student centred framework for the virtual educational universe that facilitates collaborative learning. The virtual educational world is inhabited by agents: human agents and artificial agents that interact. Agents can be mediating agents, semiotic agents or social agents;they can be intelligent software entities or simple ones, like interface agents.
The paper deals with the calculation of hysteresis power loss in cores of electromechanical converters. The analysis was carried out using the Jiles-Atherton model of ferromagnetic hysteresis incorporated into two-dim...
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The paper deals with the calculation of hysteresis power loss in cores of electromechanical converters. The analysis was carried out using the Jiles-Atherton model of ferromagnetic hysteresis incorporated into two-dimensional time-stepping finite element model. A vector hysteresis model was constructed by the vectorisation of a scalar model. The total power loss due to hysteresis was split into two component, one originating from the purely alternating magnetic field, and the second being a consequence of the local predomination of vector nature of magnetic field distribution. Two computational examples are presented showing the general applicability of the algorithm for determination of power loss distribution.
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