Wrocław University of Science and Technology
Repozytorium Eny Politechnika WrocławskaNot a member yet
431 research outputs found
Sort by
Improving Reliability with Standby Power Supplies
Get PDFThe design of electrical power supply systems is a compromise between the interests of consumers - reliability and quality of supply - and those of the supply industry - realistic investment levels and operating costs. The flexibility allowed to deviate from ‘perfect’ power quality should be used to allow cheaper and simpler supply systems; it should not be wasted by permitting poor maintenance and operating procedures to compromise reliability. Electrical equipment is designed to operate optimally under normal conditions, i.e. with a supply voltage that is within rated voltage and frequency tolerances with low voltage distortion and good phase balance and within the manufacturer’s specified environmental conditions. Operation outside these limits can result in increased losses, poor efficiency and unpredictable operation. Large deviations can cause disruption due to the false operation of protection devices. Voltage quality has a decisive influence on the operation of equipment. The voltage quality at the origin of the installation (the point of common coupling) is reduced further by the effects of other loads in the installation and the resistance of the cabling, so the voltage quality at the equipment terminals is much poorer. This is especially true in cases where loads with non-linear voltage-current characteristics are present. Disruption caused by power interruption or poor voltage quality is always inconvenient and can be serious. In hospitals there is an obvious risk to patients undergoing operations or in intensive care. Public buildings, such as cinemas, theatres, exhibition halls, etc, where people are concentrated in relatively confined and unfamiliar areas, pose a particular risk during a power failure. Manufacturing industries, especially continuous process manufacturing (paper, steel) or high technology manufacturing (semiconductors), suffer long recovery cycles following any loss of power
Inefficacy of radioactive terminals and early streamer emission terminals
Get PDFThe paper reviews about research of radioactive lightning rods carried out 30 years ago and about new measurements of early streamer emission terminals. Lightning damage on over 100 buildings equipped with ESE terminals in Malaysia and on one family house in Poland is reported. The main measure criterion was the breakdown voltage of the air gap consisted of the high voltage electrode (rod or plate) and a grounded radioactive or ESE terminal. These careful measurements show that the air gaps with ESE terminals have the same breakdown voltages as the air gaps with standard rods. Therefore the big protection zone of ESE terminals as claimed by their manufactures seem to be impossible
Probes for spot measurement of surface conductivity on polluted insulators
Get PDFThe surface conductivity of insulators in the field is often non-uniformly distributed. In this case the integral surface conductivity is not an appropriate parameter of pollution severity. A better evaluation can be achieved on the basis of local conductivity measurements by means of special probes, for example, the rod probe or tissue strip probe. In this work the form factors of different probes are given and the form factor for the rod probe was calculated. The influence of wet-contamination area, the meniscus and the pollution layer thickness on the measured value of surface conductivity are shown. It was found that the surface conductivity on polluted silicone rubber measured by a tissue strip probe is proportional to the equivalent contamination deposit density (ECDD)
The Effect of the Number of Spacer Insulators on the Breakdown Voltage of Vacuum Insulation
No full textIt was shown that when extended high voltage vacuum insulation is being considered, the effect of the he number of spacer insulators on the breakdown voltage of the system has to be taken into account. Two cylindrical electrode systems with a variable number of spacers were investigated. A very distinct decrease of the he breakdown voltage with the increase in the number of insulators was noted. This effect was much greater than could be predicted when the normal distribution of the flashover voltages of a single insulator was assumed. A much better approximation was obtained when the Weibull distribution was used
Damping of the Torsional Vibration in Two-Mass Drive System Using Forced Dynamic Control
Get PDFThe paper deals with the application of forced dynamic control strategy in the two-mass resonant system. First, the basic of the forced dynamic control theory in the case of the drive system with elastic coupling is presented. The analytical equations which allow for calculating the control structure parameters are given. The included simulation results confirm the effectives of the proposed control In order to apply the proposed control structure the information about non-measurable states is necessary. So general description of the extended Kalman filter is presented. Simulation results were confirmed experimentally in the laboratory setup
Adaptacyjne sieci neuronowe w zastosowaniu do identyfikacji stanu układów elektrycznych
Get PDFCelem pracy jest zbadanie możliwości zastosowania sieci neuronowych do estymacji parametrów sygnałów w czasie rzeczywistym, których adaptacyjny algorytm działania oparty jest na nowych kryteriach TLS i RTLS oraz zbadanie możliwości zastosowania wybranych układów sieci neuronowych do identyfikacji stanu pracy niektórych układów elektrycznych. T e z a p r a c y: Adaptacyjne sieci neuronowe umożliwiają dokładniejszą oraz szybszą identyfikację niektórych stanów pracy układów elektrycznych, aniżeli dotychczas stosowane metody
Spectral estimation of distorted signals using Prony method
Get PDFModern Frequency power converters generate a wide spectrum of harmonic components. Large converter systems can also generate non characteristic harmonics and interharmonics. Standard tools of harmonic analysis based on the Fourier transform assume that only harmonics are present and the periodicity intervals are fixed, while periodicity intervals in the presence of interharmonics are variable and very long. I n the case of frequency converters the periods of the main component are unknown. The Prony method as applied for signal analysis in power frequency converter was tested in the paper. The method does not show the disadvantages of the traditional tools and allow exact estimation the frequencies of all or dominant components, even when the periodicity intervals are unknown. To investigate the appropriateness of the method several experiments were performed. For comparison, similar experiments were repeated using the FFT. The comparison proved the superiority of the Prony method
Analysis of Non-Stationary Signals in Power Systems using Wigner Transform and Min-Norm Method
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 limitations the 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
Filtry cyfrowe
No full textCel ćwiczenia Celem ćwiczenia jest przeprowadzenie filtracji cyfrowej próbkowanych sygnałów przy wykorzystaniu środowiska programowania MATLAB® Zagadnienia do przygotowania o Próbkowanie sygnałów ciągłych, twierdzenie o próbkowaniu o Równania określające zależność pomiędzy pobudzeniem a odpowiedzią filtrów cyfrowych NOI i SOI. o Charakterystyki filtrów w dziedzinie częstotliwości
Procesor sygnałowy - wprowadzenie
Get PDFĆwiczenie jest krótkim wprowadzeniem do programowania procesora sygnałowego. Wykorzystuje się zintegrowane środowisko programistyczne: „Code Composer Studio” i „DSP Starter Kit” - układ wyposażony w procesor zmiennoprzecinkowy TMS320C6711 wraz z obsługą wejść i wyjść analogowych. Alternatywę środowiska programowania układu DSP stanowi program Simulink