Wrocław University of Science and Technology
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Silicone rubber insulators with notched surface
Full text linkA modification of an insulator profile was proposed and the advantage of a new solution was shown. The pollution flashover voltage of an insulator with small notches is about 25% higher than the flashover voltage of a flat surface. The laboratory and field tests which show the effectiveness of surface modification made on silicone rubber were described. The possibility of further surface optimization was claimed
Origin of Power Quality Disturbances
Full text linkLecture based on M.H.J. Bollen, I.Y.H. Gu: Signal Processing of Power Quality Disturbances, Wiley Interscience, 200
X-Ray Emission Accompanying the Cathode Microdischarge
No full textElectrical discharge in vacuum is accompanied by X-ray radiation and knowledge of the generation mechanism of radiation may lead to its practical use. The analysis of this phenomenon indicates that it is only at the discharge development phase until the moment of the anode plasma generation that the proper conditions for X-ray generation are satisfied. The intensity of radiation is dependent on the field current intensity on the cathode surface as well as on the value of the electron current supplying the anode. The anode current at the vacuum discharge development phase has a pulse character, and the pulse amplitude is dependent on the cathode plasma density. The radiation intensity may be increased by increasing the current amplitude, e.g. by artificial plasma generation in the trigger system
A Two-Stage Method of Localization of Sources of Harmonics in Current in a Power System
Full text linkThe paper deals with localization of sources of harmonics in a power system. At the beginning, the reasons for undertaking investigations are outlined. Then, the theoretical background of the presented method is presented. The method uses examination of the so-called voltage rate to localize the dominant harmonic source. During this examination it is assumed that (i) the voltage and current at the point of common coupling are measured, (ii) at the first stage internal impedances of equivalent sources representing the customer and utility sides are known, (iii) at the second stage only approximate knowledge of the mentioned impedances is possessed. After the principle of the method is described, features of the method are analyzed. At the end, the attention is paid to the main advantages of the method
Selected Problems of Circuit Theory Assignment No. 3 Analysis of Chosen Nonlinear System Pendulum: Due to Newton
Full text linkA pendulum is a weight suspended from a pivot so it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force will cause it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The simple gravity pendulum is an idealized mathematical model of a pendulum. This is a weight on the end of a massless cord suspended from a pivot, without friction. When given an initial push, it will swing back and forth at a constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines. A simple pendulum is an idealisation, working on the assumption that: · the rod or cord on which the bob swings is massless, inextensible and always remains taut · motion occurs in a 2-dimensional plane, i.e. the bob does not trace an ellips
Computation of Spectral Components in System with Wind Generation Unit
Full text linkSignal parameters estimation is an important prerequisite for assessment of power quality (PQ) indices. Nowadays, large amounts of measured data need to be automatically processed for appropriate and useful data mining in PQ. Especially, modern wind generators are often seen as sources of PQ disturbances, which should be constantly supervised. The authors propose an application of modified Singular Value Decomposition (SVD) method for signal parameters estimation. Results of the proposed method are compared with broadly used Fourier Transform. Additionally,, results from Prony method are presented. A mechanical model of doubly fed induction generator (DFIG), operating in various conditions was chosen as a source of disturbed signals. Research results verify the usefulness of SVD based method
Adaptation of SVD and Prony method for precise computation of current components in networks with wind generation.
Full text linkPrecise computation of current components is a key prerequisite for reliable assessment of power quality. Especially in networks with wind generation we may observe increased number of possible disturbing phenomena. This paper presents an approach to accurate computation of currents components with two similar parametric methods based on singular value decomposition (SVD) and Prony model. Those methods seem to be applicable for the detection of non integer multiples of the main frequency in decaying signals. Results of both methods have been compared and evaluated. with respect to traditional Fourier method
Identification of Out-of-Step Operation of Synchronous Machines Using High Resolution Spectrum Estimation Methods
Full text linkThe out-of-step operation conditions of a synchronous machine may occur as a result of a power system three-phase fault. The mostly used methods of identification of loss of synchronism are not secure enough. In the paper a new method using high- resolution spectrum estimation method is presented. In the case of asynchronous operation of a synchronous machine the current waveform in the stator winding can be resolved into three components, which frequencies differ insignificantly. High-resolution subspace methods enable to estimate the frequencies and on this way to identify the asynchronous operation
Odors Control with Non-Thermal Plasma Reactor
Full text linkRecent public concern about air pollution from production units has prompted more research to develop methods to reduce and control odors. Masking chemicals, oxidation processes, air scrubbers, biofilters and ventilation systems have been studied. Many new techniques for gaseous pollutants removal have been developed recently. In general, there are several industrial applications used to clean gaseous streams containing VOCs. The most common are activated carbon filters1, photocatalytic oxidation2 and non-thermal plasma systems3. Nowadays the third way is very promising because of the economic reasons and low power consumption. Non-thermal plasma processes have been investigated a lot during the past decade by many researchers for volatile organic compounds (VOCs) control in air. Many different types of low temperature reactors have been developed4. In all reactors plasma is generated and maintained by electrical discharge. In this research, the prototype non-thermal plasma reactor was proposed and its efficiency in removal of odors was calculated. The back corona discharge phenomenon was used for promoting the rise of the density of plasma in the reactor
Internetowe Laboratorium Wirtualne – programowanie urządzeń peryferyjnych wykorzystujących protokoły Modbus oraz TCP/IP
Full text linkW referacie przedstawiono adaptację dedykowanego systemu komunikacyjnego INTERBUS, przeznaczonego do wdrożenia w studenckich laboratoriach sieciowo-komputerowych wydziałów elektrycznych, ze szczególnym uwzględnieniem zagadnień z zakresu kursów z cyfrowego przetwarzania sygnałów. Podstawowym założeniem projektu było przyjęcie formuły maksymalnej zwięzłości semantyki logicznej oraz możliwość realizacji zadań laboratoryjnych z dowolnego węzła sieciowego intranetowego (LAN) lub internetowego (WAN). Dodatkowo wprowadzono opcjonalną integrację systemu z wydziałową platformą edukacyjną kształcenia na odległość