0000000000131800
AUTHOR
Andrzej Cichoń
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…
Comparative analysis of acoustic emission signals generated by electrical discharges measured by the hydrophone and the wideband contact transducer
The paper presents a comparative analysis of the acoustic emission (AE) pulses and signals generated by PDs. For this purpose the measurements of the acoustic emission signals generated by PDs were taken in the multipoint-plane system using a hydrophone placed directly in the area of discharge generation, and the AE pulses using a piezoelectric contact transducer which was on a side wall of a power transformer tub. Next, time runs and amplitude density spectra were drawn. Also the descriptors describing signals in the frequency domain were determined and the time-frequency analysis was carried out, which determined spectrograms for the energy density spectrum.
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…
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.
Measurements on partial discharge in on‐site operating power transformer: a case study
This study presents the case study of a substation in-service power transformer referred to the on-site partial discharge (PD) detection and evaluation methods. An original methodology for simultaneous application of three methods is proposed: electrical, acoustic and ultra-high frequency. Transformer is powered by the power grid and no external generator is required according to the proposed methodology. Furthermore, several possibilities of applying these concurrent measurements and benefits of such solution in terms of result interpretation, interference resistance and on-site measurement applicability are indicated. The proposed methodology allows for a fast, accurate and secure PD diag…
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.