The paper discusses the issue of analyzing the amount of gas and water contained in transformer oil. Such diagnostics include tests and measurements to verify the insulating and cooling properties of ...the oil, from which it is possible to determine the degree of transformer degradation. The experimental measurement is mainly focused on the state of the quantity of gases and water on the oil distribution transformer and their mutual ratios using monitoring and off-line measurements. In conclusion, an example of the analysis of the mechanical strength of the winding in the oil container of the aforementioned distribution transformer is the monitoring method of tracking the cooling curves through optical sensors.
The windings of power transformers must be designed so, that the effect of short-circuits currents, which can emerge in an operation, will not start up on them the destruction or the deformation of ...the mechanical or thermal character. Except for permanently deformation results of the effects of short-circuit current come to also by correct ditnensioning of electric equipment to progressive ageing. Which can make worse his mechanical properties. The article deals Ivith the diagnostic method. Which enables to anticipate such state.
Analysis problematics of transformer noise in distribution room in office building Gutten, Miroslav; Karman, Martin; Korenciak, Daniel
2023 IEEE International Conference on Environment and Electrical Engineering and 2023 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe),
2023-June-6
Conference Proceeding
The article deals with the issue of noise in offices in the building directly adjacent to the distribution transformer room. Although the standard for noise exposure is satisfactory in the work ...environment, some parts of the transformer noise at tonal frequencies around 400 Hz disturb the psyche during the activities of office workers. The article therefore dealt with acoustic measurements on two dry distribution transformers of the same power, where one of them, the "noisier" one, disturbed the employees' noise well-being. An acoustic camera was used during the measurement to determine the cause of the noisier condition of the exposed transformer. In this way, it is possible to analyze the frequency spectrum with the possibility of 3D tracking of the transformer with the identification of the place with the highest acoustic emission. The measurement was carried out with no load and with a real load for both dry distribution transformers.
The article discusses the state of transformer insulation. For a more accurate determination of the transformer insulation state are used three methods. The measurement of insulation resistance is ...the basic method and is set in the standard, value demonstrates the state of total insulation of transformer. Because the determination of moisture content of the paper insulation of transformer is very difficult process and it is necessary take a sample of paper, in this case is used method of return voltage. Return voltage measurement is more complex method and in many cases is determine a clear result very difficult. For evaluation of results have mainly impact moisture content and degree of aging of paper insulation and of course, content of conductive impurities in oil. Because the moisture content in oil is much lower than in the paper, return voltage measurement is used to determine the moisture content in paper insulation only. To confirm the results of return voltage measurement is used frequency domain spectroscopy, which clearly, according computational model, calculates the moisture content in the paper insulation.
In this paper, are described experimental results of structural changes of investigated ferrofluids based on insulating oil produced by a gas-to-liquid process and containing ferrimagnetite ...nanoparticles. Compared to normal mineral oils on the paraffinic and naphthenic base, oils derived from GTL technology are purer and have a higher lightning impulse breakdown voltage. As a carrier liquid, transformer oil (Shell Diala S4 ZX-I) with a concentration of 0.98 % ferrimagnetite nanoparticles contains investigated ferrofluid. In this experiment, dielectric spectroscopy methods were applied to obtain experimental data to investigate structural changes in Shell transformer oil as a result of an external magnetic field applied to ferrofluid. The dielectric measurements were carried out at perpendicular and parallel orientation of the electric and magnetic fields, too, and in the frequency range from 1 mHz to 10 kHz. The magneto-dielectric effect of the dielectric losses was studied, too. The changes of dielectric parameters were measured also at the linear change of the magnetic field to values up to 200 mT and anisotropy measurement.
In applications where size and weight of the electric motor are among major design concerns, Permanent Magnet Synchronous Motors (PMSMs) with wide operational speed-range are commonly preferred. Due ...to limited inverter switching frequency, high-speed operation of a drive results in a low ratio between the switching frequency and the fundamental frequency of motor voltage. Such operating conditions have been recently identified as a source of errors in determining motor current feedback using the typical technique dedicated for microprocessor-based controllers. First, sampling the phase currents synchronously with the peaks of modulation carrier provides results of mean currents under an assumption of linear current changes in steady voltage intervals. This assumption is over-simplistic in high-speed drives. Second, transforming the phase currents into a rotating reference frame, required in Field Oriented Control (FOC), is carried out using discretized rotor angle. If rotor covers a substantial angular distance in the control cycle, such simplification distorts transformation results considered as mean values. This paper analyses the joint impact of both these oversimplifications on the errors of field-oriented current components derived in a microprocessor as a feedback to the control algorithm. The analysis was carried out for a highspeed PMSM drive operating at switching frequency of 5 kHz and maximal fundamental frequency of 350 Hz. Simulation results show that the considered oversimplifications lead to notable errors in digital processing of current feedback. The direct-axis current is affected by a notable offset, while the quadrature-axis current is supplemented with a high-frequency error component.
In the article the diagnostic and measuring systems dedicated for complex output tests of power transformers aswell as their diagnostic is dcscribcd. The aim of research in this area was to elaborate ...the problem of so-called open loop measuring system controlled by PC. The attribute "open" means the possibility to adapt the system for different electric equipment, different measurands and an zdaptation of the way of monitoring, evaluation and distribution of output information according to specific requirements the controlled transformer.
The paper presents a study of the polarization current of brand-new mineral oil and moistened oil by diffusion from moistened paper-oil insulation with a moisture content of (5 ± 0.2) % by weight. ...The oil moistening method used in the study enabled the maximal reproduction of phenomena occurring in transformers. Based on the obtained measurement results, the temperature dependencies of the DC conductivity and the activation energy values of the conductivity of the brand-new and moistened oil by diffusion were determined. The obtained measurement results indicate a change in the activation energy of conductivity due to the moistening of the oil, which may significantly affect the accuracy of determining the moisture content of transformer insulation
In the article is description of the contact analysis of power transformers 22/0.4 kV with insulation oil-paper by time impact tester and frequency impedance analyzer. Both methods are most often ...used for the analysis of mechanical components (mainly windings) of power transformers. The diagnostic measurement allows finding fault state in transformer parts. Theoretical and experimental research at power transformer by frequency and time area is presented. Within analysis, mutual courses comparisons for both methods were performed using mathematical correlation methods. Thanks to this mathematical analysis, an interthread short circuit was found on the transformer primary winding.
Methods of Humidityanalysis in Transformer Oil
Komunikácie : vedecké listy Žilinskej univerzity = Communications : scientific letters of the University of Žilina,
6/2010
Journal Article
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