0000000000131801
AUTHOR
Tomasz Boczar
The influence of the momentum coefficient and the number of the averaging points of the power spectrum density on the recognition effectiveness of the AE signals generated by basic PD forms by the neuron network
The subject matter of this paper refers to the next stage of the research work connected with the improvement of the acoustic emission method (AE) used for the evaluation of partial discharges (PDs) generated in paper-oil insulation systems of high-voltage power appliances. The subject matter discussed here refers to one of the aspects of the analysis of the signals registered - a correct and effective recognition of the AE signals generated by basic PD forms. The paper presents research results of the application of the unidirectional artificial neuron networks (ANN) used for the recognition of basic PD forms that can occur in paper-oil insulation impaired by aging processes.
The influence of the propagation path length on the results of the time–frequency analysis of the acoustic emission generated by partial discharges in insulation oil
The paper presents the measurement results of the acoustic emission (AE) signals generated by partial discharges (PDs) at various thickness of the oil insulation layer. For the AE signals registered the time - frequency analysis was carried out based on the use of the short-time Fourier transform (STFT). Two- and three-dimensional spectrograms of the power spectrum density and the amplitude spectrum were determined. The evaluation of the influence of the propagation path length of the AE signal on the results of the time - frequency analysis was performed through the analysis of the spectrograms determined.
Modeling and Experimental Verification of Ultrasound Transmission in Electro Insulation Oil
A verification study of ultrasound transmission numerical simulation results with experiment results is presented in this paper. The work considers a model of a transformer tank which is filled with electro insulating oil. In the experiment, performed under laboratory conditions, an ultrasound wave is generated by a piezoelectric transducer that is fixed in the centre of the tank and measured by another transducer mounted inside the tank at three distances: 10, 20 and 30 cm from the sound source. The transducer is able to measure and generate acoustic waves in the ultrasound frequency band up to 1 MHz. The simulation considers numerical calculation of acoustic pressure distribution inside t…
The possibilities of using the acoustic emission method in expert systems for the evaluation of insulation systems of power transformers
The paper presents the range and possibilities of using expert systems at diagnostic measurements of insulation systems of power appliances taken by the acoustic emission (AE) method. Multi-parametric descriptors characterizing the AE signals, which can be used in the knowledge base as criteria making the identification of basic partial discharge forms (PDs) possible, have been characterized in detail. The tables show descriptors describing the AE signals registered in time, frequency, time-frequency domains and statistical data. Moreover, computational tools that can be used in the process of conclusion drawing were suggested and the range of the research work done by the authors of the pa…
ECT of ethanol and hexane mixtures in the spinning disk system
The paper presents the research results of electrostatic charging tendency (ECT) of ethanol and hexane mixtures, a liquid of a simple chemical structure and high purity (pro analysis). The research work was carried out in a spinning disk system, where the factors influencing the value of the electrification current registered were the composition of the mixture and the rotational speed of the disk. The research results showed that the biggest ECT changes occur in the range of up to 10% of ethanol content in hexane and the electrification current characteristic has a visible maximum for the mixture, the contents of which constitute 95% of hexane volume and 5% of ethanol by volume. In the nex…
Identification of a specific type of PD from acoustic emission frequency spectra
The paper presents an attempt to apply spectral analysis tools in processing acoustic emission (AE) pulses generated by partial discharge (FD). The experimental part of the paper describes spark gaps generating four types of PD and specifies parameters of measured acoustic signals and recalls the system used for measurement and analysis of the frequency spectra. Also, a spectral analysis procedure is presented, and frequency-domain descriptors characterizing AE pulses are defined. The results of the analysis are given both as time plots and amplitude and energy density spectra, related to values of the associated descriptors. The spectral analysis results cover AE pulses generated in system…
Objectivization of the electrical discharge measurement results taken by the acoustic emission method
The subject matter of this paper refers to the improvement of the acoustic emission method (AE) in its application for diagnostics of insulation systems of power appliances whereas the detailed subject matter is connected with determining the possibilities and indicating the range of using statistical and digital methods of signal processing for the evaluation of the AE pulses generated by partial discharges (PDs), which can occur in paper-oil insulation of power transformers.
The repeatability and reproducibility of calibrating signals generated by Hsu-Nielsen method
During the measurements of the acoustic emission signals taken both in the laboratory and industrial conditions it is necessary to carry out calibration of the measurement paths used. One of the basic calibration methods is the one invented by Hsu-Nielsen, which consists in generating an acoustic signal during breaking a scriber placed in a special head put on an automatic pencil. The paper presents the measurement results of acoustic signals taken at various structural parameters of calibrating heads, which was done to determine their influence on the repeatability of the results obtained. Moreover, the measurements were taken for ten identical, in relation to their geometrical measurement…
Technical Possibilities of Reducing the Sound Pressure Level Emitted into the Environment by a Power Transformer
The subject presented in this paper refers to measurements and assessment of the corrected sound pressure level values (noise) occurring around a medium-power transformer. The paper presents the values of noise accompanying the operation of the power object before and after its modernization, which consisted in repeated core pressing and replacement of the cooling system. The main aim of the research work was the assessment of the influence of the repair work on the noise level emitted into the environment.
Application of wavelet analysis to acoustic emission pulses generated by partial discharges
The subject matter of this paper refers to the improvement of the acoustic emission (AE) method when used for detection, measurement and location of partial discharges (PDs) in oil insulation systems of power appliances. The detailed subject matter refers to the issues connected with the application of modern methods of digital processing of signals obtained during technical high-power measurements. The paper presents the results of measurements and analyses of the AE pulses generated in setups making the modeling of basic PD forms that can occur in oil insulations possible. The research concentrated mainly on the following types of PDs: point-plane, multipoint-plane, multipoint-plane with …
The influence of the temperature of insulation oil on the results of measurements of the acoustic emission signals generated by partial discharges
The subject matter of this paper refers to the improvement of the acoustic emission method (AE) used for evaluation of partial discharges (PDs) generated in paper-oil insulation systems of power appliances. The paper presents the measurement and analysis results of the AE signals generated by partial discharges of the surface type (SPDs). The AE signals were measured on the surface of a transformer tub using a broad-band contact transducer, and then they were subject to a time-frequency analysis. The measurements were taken while heating transformer oil in the range from 30 to 85°C with gradation of every 5°C. For time runs, amplitude and energy density spectra the descriptor values that ch…