Wrocław University of Science and Technology
Repozytorium Eny Politechnika WrocławskaNot a member yet
431 research outputs found
Sort by
Pollution test station Glogow, twenty years of research
Get PDFThe evaluation of electrical stress of polluted outdoor insulators was carried out at the field test station located at a copper smelting plant Głogów in 1987 and 2002. Leakage current and flashover voltages were recorded on porcelain long rods of different types. A simple impulse counters having three different trigger levels were used for current measurements. The special fuses with an explosion mixture were applied for detection of flashovers. Additionally, the measurements of ESDD on insulator surface or dust deposition density were carried out. During last ten years the industry dust emission in Middle Europe decreased considerably due to progress in environmental protection. Therefore the similar measurements were repeated with the aim to asses the current state of electrical stress of outdoor insulators
Synthesis of Circuits
Get PDFDetailed content: Passive Circuits Strategy of filter design System functions, realizability. Hurwitz polynomials Passive One-port networks Cauer synthesis procedure Passive Two-port networks Prototype filters Impedance scaling Frequency scaling Transient response Two-port reactive circuit synthesis Butterworth and Chebyshev approximations Frequency transformations Active circuits Operational amplifiers Active two-terminal networks Impedance converters and inverters, gyrator, negative elements Active filters 2nd order sections. Sallen-Key circuit, Universal Active-RC Biquad Digital filters Recursive and non-recursive filters. Aliasing. Windows. Digital transfer function, Z-transform Design of non-recursive filters Design of recursive filter
Robust Control of an Electrical Drive using Adaptive Fuzzy Logic Control Structure with Sliding-Mode Compensator
Get PDFIn the paper a robust control system with the fuzzy adaptive controller and the additional compensator is presented. A model reference adaptive control system (MRAC) is applied to a drive system with changeable parameters. The speed controller is based on the neurofuzzy network. The additional compensator relaying on the sliding-mode theory is used to improve the dynamical characteristics of the drive system. The proposed control structure is investigated in simulation and experimental tests
Spectrum estimation of non- stationary signals in power systems
Get PDFTime-varying spectra of non-stationary time-series commonly used are spectrograms from the Short-Time Fourier Transform (STFT). The most prominent limitation of the Fourier Transform is that of frequency resolution. To overcome the limitation the Wavelet Transform, Wigner-Ville Distribution and the Min-Norm subspace method have been applied for spectrum estimation of non-stationary signals caused by switching on capacitor banks and by a short circuit at the output of a frequency converter. Investigation results confirm the advantages of the advanced methods
Rapid dissolved gas analysis by means of electrochemical gas sensors
Get PDFRapid, introductory analysis of gases dissolved in insulating oil DGA carried out in the field can help in effective screening of faulty transformers as well as minimising number of classical laboratory chromatographic DGA tests. It is also crucial for shortening a time gap between oil sampling and its analysis. A novel approach to DGA is presented in this paper. A rapid analysis of oil samples is carried out by means of a portable analyser fitted with electrochemical gas sensors. Extraction of gases from the oil matrix is achieved by means of a dynamic, closed loop stripping process. The analyser, which was built, is controlled by a microprocessor and may be operated in the field as an autonomous device. The system incorporates only two gas sensors and due to an extended set of their output signal wave descriptors used for the analysis it allows for a reliable identification of fault gases present in an oil sample. The identification of basic transformer fault types is illustrated on the basis of analytical results obtained for artificial oil samples prepared in a laboratory as well as those taken from transformers in-operation
On-line determination of Symmetrical Components by Sampling
No full textSymmetrical components of currents and voltages are used for the performance analysis of three-phase power systems (positive-sequence component) and for protection. This paper introduces different algorithms permitting to determine in real time the symmetrical components from few sampled triplets of voltages or currents. By using elaborated algorithms both parasitic harmonics and transients can be suppressed. Finally the attention is given to a general approach to the implementation of a algorithm with a pilot multi-processor equipment
Ultrasonic Non-Destructive Diagnostics of HV Insulators
Get PDFThe paper presents non-destructive ultrasonic method for investigations of long-rod insulators, operated on overhead power lines and stations. It was established correlation between the degree of C 120 porcelain material degradation and the parameters of ultrasonic wave propagation and attenuation. As example of application of the method there were presented ultrasonic examinations of two groups of insulators – 15 line and 49 station post. On the basis of the measurements advancement of ageing degradation of the material and the quality of the tested insulators were ascertained
Impact of Distributed Generation on Electrical Power Network
Get PDFIn today’s world, the demand for the electric power is growing rapidly; to overcome this, many power generation resources are constructing in all over the globe. But the problem arises when the new generation is integrated with the power network and distribution, as the existed power network was not designed by keeping in mind the new integration of generation in the future. The objective of this paper is to discuss some of the problems associated with distribution resources on the power and network
Wind Power Generation-related Power Quality Issues
No full textAs a promising renewable alternative, the wind power is highly expected to contribute a significant part of generation in power systems in the future, but this also bring new integration related power quality issues, which mainly consist of power flow fluctuation analyzed with current, voltage fluctuation and flicker severity factor (P lt and P st ) as ‘ case study ’ , by its comparatively new characteristics, due to the fluctuation nature of the wind (velocity) and the comparatively new type of its generators (currently popular type of squirrel-cage induction). One practical solution to mitigate the wind generation i ntegration related power quality issues is introduced in this paper, by using Energy Storage System (ESS)