http://zet10.ipee.pwr.wroc.pl Electrical Engineering Repository latest documents pl Wed, 14 Jul 2021 19:59:10 CEST CDS Invenio 0.92.1 zbigniew.leonowicz@pwr.wroc.pl 1440 http://zet10.ipee.pwr.wroc.pl/img/cds.png http://zet10.ipee.pwr.wroc.pl Search this site: p http://zet10.ipee.pwr.wroc.pl/search http://zet10.ipee.pwr.wroc.pl/record/458Nieostrożne używanie sprzętu elektrycznego, naprawa urządzeń i instalacji elektrycznej przez osoby nie posiadające odpowiednich kwalifikacji, powoduje, że prąd elektryczny może stać się śmiertelnym zagrożeniem. Przyczyną około 70 % wypadków porażenia lub poparzenia prądem elektrycznym jest niewłaściwe postępowanie człowieka, wynikające z braku umiejętności, lekkomyślności lub niedoskonałością techniczną rozwiązań instalacji elektrycznych. Dlatego podstawowa znajomość przepisów bezpieczeństwa w tej dziedzinie powinna być znana społeczeństwu. Miarą oceny stanu bezpieczeństwa pod względem porażeniowym w skali kraju jest liczba wypadków śmiertelnych przypadających na milion mieszkańców w ciągu roku. W Polsce wskaźnik ten wynosi obecnie około 7,5. W innych, najbardziej uprzemysłowionych krajach Europy, tylko 1,3 – 2,0. W kraju wybucha też corocznie wiele tysięcy pożarów mieszkań i całych obiektów budowlanych, znaczna ich część, bo około 30%, jest przypisywana wadom instalacji i urządzeń elektrycznych. Jest to udział znacznie większy niż w innych krajach Europy. Stale prowadzone są prace nad poprawą jakości oraz skuteczności działania urządzeń i systemów ochrony przeciwporażeniowej. Może w przyszłości, dzięki temu doczekamy się w 100 % bezpiecznych instalacji elektrycznych. Adresatem niniejszej pracy są osoby, które chciałyby zapoznać się z podstawową wiedzą z zakresu zabezpieczenia instalacji fotowoltaicznej, szczególnie przy pracy na sieć (grid-on) jak również wszystkich wykonawców, którzy tę wiedzę posiadają, ale chcieliby ją przypomnieć i uporządkować.Tomaszewski, TTue, 13 Oct 2015 06:08:23http://zet10.ipee.pwr.wroc.pl/record/458 http://zet10.ipee.pwr.wroc.pl/record/457This paper presents the mathematical modeling of photovoltaic (PV) module with the effective comparison of two popular maximum power point tracking (MPPT) techniques; Generally, Maximum Power Point Tracking (MPPT) techniques are used in PV System to extract maximum possible power which in turn depends on solar irradiance and temperature of PV module. Two most widely used MPPT techniques namely incremental conductance (INC), and perturb & observe (P&O) method are analyzed in this paper. The PV models compared are simplified single diode model, improved two diode model and simplified two-diode model. The effectiveness of the comparison has been done through MATLAB/Simulink Environment and the results are analyzed.Chitti Babu, BThu, 18 Jun 2015 10:12:08http://zet10.ipee.pwr.wroc.pl/record/457 http://zet10.ipee.pwr.wroc.pl/record/456The article presents the AC power measurements based on physical definitions as introduced by the draft German standard DIN 40110 in 1970 and its practical application as a power signal processor. The power processor is an electronic device allowing separation of the measured power signal (obtained from the multiplier circuit of voltages and currents) in two components: P+ and P- defined as the input power Pv and return power Pr. The separation is obtained by shifting the phase angle between the current and voltage. The value of return power is negative. Such separation is natural because it is based on physical phenomena of delivered, useful energy and harmful return energy flows. Return power is considered harmful because it causes heating of cables and sources of AC power (as transformers). Presented concepts and meters can be useful for accurate billing purposes for delivered electrical energy as well as for dynamic compensation of nonlinear loads to reduce the return power. Experiments realized using the power meter WL-1 synchro (operating according to physical definitions) confirms high percentage of return power for nonlinear loads, as AC powered LED light sources where the amount of return power can reach 70% of delivered power.Kolanko, JThu, 18 Jun 2015 09:35:08http://zet10.ipee.pwr.wroc.pl/record/456 http://zet10.ipee.pwr.wroc.pl/record/455A fast and exact detection of phase and fundamental frequency of grid voltage/current is essential for calculating accurate reference signal in order to implement the control algorithm of inverter-interfaced distributed generation (DG) system and realize precise harmonic compensation. However, the methods adapted in the literature based on phase locked loop (PLL) exhibits large phase error, be difficult to implement, and their performance is also indistinct under conditions where the grid frequency varies or the supply is distorted with low frequency harmonics. This paper explores an improved phase detection system for DG system based on Sliding Discrete Fourier Transform (SDFT). The proposed SDFT based phase detection shows a robust phase tracking capability with fast transient response under adverse situation of the grid. Moreover, SDFT phase detection system is more efficient as it requires small number of operations to extract a single frequency component, thereby reducing computational complexity and simpler than DFT. The superior performance of proposed SDFT phase detection system is analysed and the obtained results are compared with Discrete Fourier Transform (DFT) filtering to confirm the feasibility of the study under different grid environment such as high frequency harmonic injection, frequency deviation, and phase variation etc.Chitti Babu, BFri, 17 Oct 2014 11:02:43http://zet10.ipee.pwr.wroc.pl/record/455 http://zet10.ipee.pwr.wroc.pl/record/454A converter-interfaced distributed generation (DG) system, like, wind power system, photovoltaic (PV) and micro-turbine-generator system, requires a fast and exact detection of phase and fundamental frequency of grid current in order to implement the control algorithm of power converters by generating reference currents signals. Moreover, a desired synchronization algorithm must detect the phase angle of the fundamental component of grid currents as fast as possible while adequately eliminating higher order harmonic components. This paper presents a grid synchronization algorithm for converter-interfaced DG systems based on recursive Discrete Fourier Transform (DFT) filtering. The proposed recursive DFT filtering shows a robust phase tracking capability with fast transient response under abnormal grid conditions. The overall performance of studied recursive DFT filtering is analysed and the obtained results are compared with Synchronous rotating reference frame (SRF) PLL to confirm the feasibility of the study under different grid environment such as high frequency harmonic injection and frequency deviation.Chitti Babu, BFri, 17 Oct 2014 10:42:25http://zet10.ipee.pwr.wroc.pl/record/454 http://zet10.ipee.pwr.wroc.pl/record/453Using of mathematical transformations and digital signal processing (DSP) methods of recorded voltage and currents in power systems in order to extract important informations about physical processes is already known. Higher resolution of measurements and massive introduction of PMU devices in the power systems allows appliance of DSP - based fault location methods in complex power networks. High availability of power systems is required in the modern societies. Fast fault location algorithms and consequent fast repairing of faults is necessary condition for high availability of power networks. Here is represented a numerical procedure for fault location and testing of method already introduced in scientific literature on complex configuration of power network consisting of XLPE underground submarine and land cables between land and offshore substation connecting large wind park with main power system.Bernadić, ASat, 24 May 2014 01:14:17http://zet10.ipee.pwr.wroc.pl/record/453 http://zet10.ipee.pwr.wroc.pl/record/452This paper presents the developed and built comprehensive system of registration, archiving and data processing for the wide-area monitoring of power quality in a separated part of real power grid with distributed renewable generation. Real case studies related to localization of sources of voltage disturbances are presented.Leonowicz, ZSat, 24 May 2014 01:07:14http://zet10.ipee.pwr.wroc.pl/record/452 http://zet10.ipee.pwr.wroc.pl/record/451Wind power generation systems influence power quality in a very specific manner creating the requirements for detailed and correct analysis of disturbances caused by wind generators. Wind power system cause sub- and interharmonic disturbances within the spectrum of voltages and currents. The paper shows alternative method of spectrum estimation in power systems, tested on the system with the doubly fed induction generator (DFIG) connected to low voltage distribution grid. Advanced spectral estimation algorithm (ESPRIT) are applied to overcome the drawbacks of Fourier-based techniques.Leonowicz, ZWed, 20 Nov 2013 16:18:52http://zet10.ipee.pwr.wroc.pl/record/451 http://zet10.ipee.pwr.wroc.pl/record/448During passing gas bubbles through suspensions containing hydrophobic or/and hydrophilic particles, some mechanical carryover of particles to the froth layer always takes place. The entrainment of mineral particles is influenced by many parameters, mostly by the particle size and the concentration of the frother. The paper deals with influence of methylisobutylcarbinol (MIBC), a common and standard laboratory flotation tests frother, on the mechanical carryover of quartz, a typical gangue mineral component of ores. Entrainment tests were carried out in a laboratory Mechanobr flotation machine with quartz particles suspended either in water or frother solution. The mechanical recovery of quartz in the frother increased with time and reached plateau after about 20 minutes of flotation. The plateau level of quartz recovery depended on the frother concentration. Initially it is observed an increase of the plateau with frother concentration until it reaches the highest plateau level at about of 32 % of quartz recovery. The shape of flotation kinetics, the plateau level of the quartz entrainment after long (about 20 min) bubbling time and at sufficiently high concentration (above about 510-4 M MIBC) can be used as parameters to characterize the ability of frothers to entrainment of particles. In the studied system of quartz-MIBC-Mechanobr flotation cell at 20 min of flotation and 510-4 M of MIBC, the maximum entrainment is 32 %. These parameters can be useful for evaluation of the mechanical recovery of particles in flotation systems. Surface chemistry of frother interaction with minerals in relation to mechanical recovery of particles will be discussed.Szyszka, DTue, 29 Oct 2013 18:03:20http://zet10.ipee.pwr.wroc.pl/record/448 http://zet10.ipee.pwr.wroc.pl/record/447Z przeglądu dotychczasowych badań oraz badań opisanych w tym artykule, wynika że wzrost stężenia spieniacza powoduje nasilenie flotacji mechanicznej; ponadto istnieje pewne stężenie graniczne, przy którym krzywa zależności wychód stężenie spieniacza osiąga plateau. Każdy spieniacz flotacyjny można scharakteryzować jedną liczbą charakterystyczną dla niego przy odpowiednim stężeniu tego spieniacza. Określenie wartości stężenia granicznego maksymalnej flotacji mechanicznej jest bardzo pożądane, gdyż może to być bardzo użyteczny parametr do opisu wyniesienia mechanicznego. Znaleziono związek pomiędzy stężeniem stosowanych odczynników pianotwórczych i wyniesieniem mechanicznym kwarcu. Potwierdzono, że przy długim czasie flotacji występuje tzw. graniczna flotacja mechaniczna, czyli największa możliwa do uzyskania w danym układzie flotacyjnym.Szyszka, DTue, 29 Oct 2013 12:12:51http://zet10.ipee.pwr.wroc.pl/record/447