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1
Content available remote Application of wavelet transform for identification of single phase-to-ground fault in compensated networks
Osipov Dmitry S., Kovalev Vladimir Z., Arkhipova Olga V., Dolgikh Nadezda N.
Przegląd Elektrotechniczny
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2021
|
R. 97, nr 6
34--38
EN
In a number of EU countries medium voltage networks operate in the compensated neutral mode. In that case an arc suppression coil is commonly shunted with a resistor. The most common type of damage to such networks is a single phase-to-ground fault. The paper presents the method for two stage identification of a line where the fault has occured. The first stage is based on the analysis of high frequency components arising under transients. At the first stage a continuous wavelet transform is used to find frequencies. The second stage involves an analysis of the steady-state mode of a single phase-to-ground fault. Based on the energy spectrum of higher harmonics a damaged line is detected. To determine the energy spectrum at the second stage of the work a wavelet packet transform is applied. Wavelet transform has a number of advantages compared with short-time Fourier transform (STFT), particularly when analyzing non-stationary modes. The proposed method can be implemented to organize digital protection against ground faults.
PL
Sieci średniego napięcia w wielu krajach UE działają w skompensowanym trybie neutralnym. W takim przypadku cewka gasząca łuk jest zwykle bocznikowana przez rezystor. Najczęstszym rodzajem uszkodzeń w takich sieciach jest zwarcie jednofazowe do ziemi. W artykule przedstawiono technikę dwuetapowej identyfikacji linii, na której nastąpiło uszkodzenie. Pierwszy etap opiera się na analizie składowych wysokiej częstotliwości powstających pod wpływem stanów nieustalonych. W pierwszym etapie do znalezienia częstotliwości używana jest ciągła transformata falkowa. Drugi etap obejmuje analizę stanu ustalonego pojedynczego zwarcia międzyfazowego. Na podstawie widma energii wyższych harmonicznych wykrywana jest uszkodzona linia. Do wyznaczenia widma energii w drugim etapie pracy stosuje się transformację pakietu falkowego. Transformacja falkowa ma wiele zalet w porównaniu z krótkotrwałą transformatą Fouriera, szczególnie w przypadku analizy modów niestacjonarnych. Zaproponowaną metodę można zaimplementować do organizacji cyfrowej ochrony przed zwarciami doziemnymi.
2
Content available Behavior of single-point harmonic producer indicators in electrified AC railways
Mariscotti Andrea
Metrology and Measurement Systems
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2020
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Vol. 27, nr 4
641--657
EN
Electrified railways are an example of AC single phase distribution networks. A non-negligible amount of active and nonactive power may be related to harmonics, especially for distorted highly-loaded systems. The paper considers the relevance of the harmonic power terms in order to identify distortion sources in a single-point perspective, in line with the approach of EN 50463 for the quantification of the power and energy consumption. Some single-point Harmonic Producer Indicators (HPI) based on harmonic active power direction and nonactive distortion power terms are reviewed and evaluated using pantograph voltage and current measured during several hours of runs in two European AC railways (operated at 16.7 and 50 Hz). The HPI based on active power shows to be consistent and provides detailed information of rolling stock characteristic components under variable operating conditions; those based on nonactive distortion power are global indexes and hardly can operate with complex harmonic patterns in variable operating conditions.
3
Content available Measurement-based harmonic current modeling of mobile storage for power quality study in the distribution system
Wenge C., Guo H., Roehrig C.
Archives of Electrical Engineering
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2017
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Vol. 66, nr 4
801--814
EN
Electric vehicles (EVs) can be utilized as mobile storages in a power system. The use of battery chargers can cause current harmonics in the supplied AC system. In order to analyze the impact of different EVs with regardto their number and their emission of current harmonics, a generic harmonic current model of EV types was built and implemented in the power system simulation tool PSS®NETOMAC. Based on the measurement data for different types of EVs three standardized harmonic EV models were developed and parametrized. Further, the identified harmonic models are used by the computation of load flow in a modeled, German power distribution system. As a benchmark, a case scenario was studied regarding a high market penetration of EVs in the year 2030 for Germany. The impact of the EV charging on the power distribution system was analyzed and evaluated with valid power quality standards.
4
Content available Three phase active power filter with selective harmonics elimination
Sozański K.
Archives of Electrical Engineering
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2016
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Vol. 65, nr 1
33--44
EN
This paper describes a three phase shunt active power filter with selective harmonics elimination. The control algorithm is based on a digital filter bank. The moving Discrete Fourier Transformation is used as an analysis filter bank. The correctness of the algorithm has been verified by simulation and experimental research. The paper includes exemplary results of current waveforms and their spectra from a three phase active power filter.
5
Content available remote Passive Power Filter Design Using Genetic Algorithm
Klempka R.
Przegląd Elektrotechniczny
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2013
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R. 89, nr 5
294-301
EN
Continuous technological development facilitates the increase in the number of nonlinear loads that significantly affect the power quality in a power system and, consequently, the quality of the electric power delivered to other customers. One of the most common methods to prevent adverse effects of nonlinear loads on the power network is the use of passive filters. Design of such filter can be regarded as a multi-criterial optimisation task, to which genetic algorithms can be employed. Watching recent tendencies in science can be observed an increasing number of "artificial intelligence" applications to practical solutions. It has been therefore decided to apply genetic algorithms (GA) to passive power filter design as an example of GA usefulness for technical issues. The paper presents passive filter structures designed using a program developed by the author in the MATLAB environment employing genetic algorithm. Two methods of approaching the design goal are presented - traditional and GA.
PL
Śledząc tendencje współczesnej nauki, można zauważyć zwiększającą się ilość zastosowań „sztucznej inteligencji” w praktycznych rozwiązaniach. Idąc w tym kierunku, zdecydowano się zastosować Algorytmy Genetyczne (AG) do projektowania pasywnych filtrów energetycznych jako przykład użyteczności AG w zagadnieniach technicznych. Projektowanie takiego filtru można potraktować jako zadanie optymalizacji wielokryterialnej, do rozwiązania, którego można użyć Algorytmy Genetyczne. Artykuł przedstawia przykładowe struktury filtrów pasywnych, zaprojektowanych za pomocą opracowanego przez autora, w środowisku Matlab, programu wykorzystującego AG. Przedstawiono dwie metody podejścia do postawionego zadania projektowego.
6
Content available remote Generic Model of Coastal Distribution Network for Power System Harmonics Studies
Strugar V. L., Katic V. A., Milanovic J. V.
Przegląd Elektrotechniczny
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2013
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R. 89, nr 1a
149--155
EN
The paper presents a generic model of typical coastal distribution network developed for power quality studies. Its composition is based on number of measurements performed over long period of time at different connection points in existing distribution network. All relevant elements of the network are fully described and discussed. The generic model can be used for benchmarking results of power system studies, in particular harmonic studies, for coastal regions network including specific types of consumers like hotels, resorts, marinas, airports, apartment buildings, market centres and moderate size industrial plants.
PL
W artykule zaprezentowano typową nadmorską sieć przesyłową z przeznaczeniem do analizy jakości energii. Opisano dokładnie wszystkie elementy sieci oraz długookresowe wyniki badań. Celem jest analiza takiej sieci z uwzględnieniem jej typowych odbiorców takich jak hotle, centra handlowe, apartamentowce itp.
7
Content available remote Heuristic Optimization Techniques to Determine Optimal Capacitor Placement and Sizing in Radial Distribution Networks: A Comprehensive Review
Sirjani R., Mohamed A., Shareef H.
Przegląd Elektrotechniczny
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2012
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R. 88, nr 7a
1-7
EN
Capacitors in power systems are used to supply reactive power to minimize loss and to improve the voltage profile. The appropriate placement of capacitors is also important to ensure that system power losses and total capacitor costs are minimal. The capacitor placement problem is commonly solved using heuristic optimization techniques which are diverse and have been the subject of ongoing enhancements. This paper presents a survey of the literature from the last decade that has focused on the various heuristic optimization techniques applied to determine optimal capacitor placement and size.
PL
Kondensatory używane są w sieciach zasilających do poprawy jakości napięcia – zmniejszenia mocy biernej. Ważną rolę odgrywa umiejscowienie kondensatora. W artykule zaprezentowano przegląd literaturowy prac na temat metod optymalizacji umożliwiających określenia optymalnej pozycji i wielkości kondensatora.
8
Content available remote A New Method for the C-Type Passive Filter Design
Klempka R.
Przegląd Elektrotechniczny
|
2012
|
R. 88, nr 7a
277-281
EN
The paper presents the new C-type high harmonic power filter design process whose aim is the reduction of total harmonic distortion in an industrial power supply system. A new method for C-type filter design is proposed and an example of the method application to an industrial plant is provided. The basis for the new algorithm is assuming, at the design phase, the required distribution of the harmonic current between the filter to be tuned to that harmonic and the supply network. This method takes into consideration the network equivalent impedance.
PL
Niniejszy artykuł przedstawia projektowanie energetycznego filtru typu C wyższych harmonicznych, którego zadaniem jest zmniejszenie współczynnika zawartości harmonicznych w przemysłowym systemie zasilania. Zaproponowano nową metodę projektowania C-filtru oraz przedstawiono przykład zastosowania tej metody projektowania w praktyce dla zakładu przemysłowego.
9
Rezystancyjny dzielnik napięcia do pomiarów wyższych harmonicznych w sieciach 400 kV
Błajszczak G., Olak J.
Energetyka
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2011
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nr 8
473-476
PL
Przedstawiono szczegółowy opis rezystancyjnego, pomiarowego dzielnika napięcia. Dzielnik został zaprojektowany i zbudowany przez firmę Transformex przy współpracy z PSE Operator i jest przeznaczony do pracy w sieciach 400 kV. Zadaniem dzielnika jest obniżenie badanego napięcia do wartości akceptowalnej przez elektroniczne urządzenia pomiarowe. Dzięki charakterystyce niezależnej od częstotliwości, dzielnik może służyć do precyzyjnych pomiarów odkształceń napięcia. Przedstawiono charakterystyki pomiarowe dzielnika.
EN
The paper presents a detailed description of a resistive divider that was designed by Transformex Sp z o.o. with collaboration of PSE Operator S.A. The measurements at 400 kV require linear voltage reduction to the value acceptable by electronic equipment. The divider will be used for upmarket accurate measurements of higher harmonics and other voltage distortions. It can be also used for evaluation and correction of frequency characteristics in traditional measure transformers.
10
Content available Study on Hybrid Filtering Solution for Marine Electric Network
Xu X - Y., Mindykowski J., Chen C. L. P.
Polish Maritime Research
|
2010
|
nr 2
72-78
EN
This paper presents a Hybrid APF/PFC/PPF Circuit (active power filtering and power factor correction circuit aided by shunt passive filter) for harmonic suppression and power factor correction in a marine electric network. By employing the proposed hybrid circuit, marine electric power network voltage and current can be maintained as being sinusoidal, and the power factor is close to 1. The effectiveness of the proposed method that is applied to a marine electric network is demonstrated through a simulation experiment. The results show that the expected performances are achieved.
11
Content available remote Metoda konstrukcji częstotliwosciowych modeli nieliniowych wielobiegunników
Walczak J., Świszcz P.
Przegląd Elektrotechniczny
|
2009
|
R. 85, nr 4
227-233
EN
Analysis of processes occurring in electric and electronic power systems requires knowledge of nonlinear elements which are the main source of distortion of currents and voltages. The purpose of the article is to present a method of construction of frequency models of nonlinear multipoles. The worked out theory assumes a mathematical description of characteristics of a nonlinear element. In order to obtain parameters of frequency models for multipoles the theory of describing functions has been used.
PL
Analiza procesów wystepujących w układach elektrycznych i energoelektronicznych wymaga znajomości nieliniowych elementów, które są główną przyczyną powstawania zniekształceń prądów i napięć. Celem tego artykułu jest zaprezentowanie metody konstrukcji częstotliwościowych modeli nieliniowych wielobiegunników. W celu wyznaczenia parametrów modeli zastosowano metodę funkcji opisującej.
12
Content available Wind turbine harmonics caused by unbalanced grid currents
Dettmann K. D., Schostan S., Schulz D.
Electrical Power Quality and Utilisation. Journal
|
2007
|
Vol. 13, nr 2
17-23
EN
For wind turbines that feed into public grids limits for voltage and current harmonics must be assured. To verify that the actual levels are valid, measurements are necessary. Problems can occur to determine which part of these harmonics has its origin in the wind turbine. It is shown that also harmonics which originally have zero sequences can be transferred over a delta-star-transformer, if the currents of the wind turbine are asymmetric due to unbalanced loads. Measurements in an existing wind turbine configuration are discussed, which confirm the described effects.
13
Analysis of instantaneous spectrum of non-stationary electrical signals
Sikorski T., Łobos T., Ruczewski P.
Poznan University of Technology Academic Journals. Electrical Engineering
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2006
|
No 52
7-19
EN
This paper serves the idea of applying joint time-frequency representations for analysis of non-stationary signals in electrical engineering. Main directions of researches are concentrated around Cohen's class of transformation that gives some possibilities of adaptation to analysed signal by choosing appropriate kernel function. Performed theoretical discussion allowed to suggest affine subclass of Cohen's family as a particularly useful for electrical engineering area. In order to investigate the methods several experiments were performed using simulated phenomena of switching on the capacitor banks in distribution system. Firstly the influence of different kernel functions was investigated when Wigner-Ville, Choi-Williams and Zhao-Atlas-Marks distributions were applied. Then some aspect of additional smoothing operations was introduced with comparison to classical spectrogram. Proposed methods allowed to track instantaneous frequency as well as energy with better time-frequency precision than classical spectrogram. It leads to applications in diagnosis and power quality area.
14
Content available Power Electronics Harmonic Analysis Based on the Linear Time Periodic Modeling. Applications for AC/DC/AC Power Electronic Interface
Ignatova V., Granjon P., Bacha S.
Electrical Power Quality and Utilisation. Journal
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2006
|
Vol. 12, nr 1
45-51
EN
This paper presents an analytical frequency-domain method for harmonics modeling and evaluation in power electronic systems. The considered system is described by a set of differential equations, which are converted in the frequency domain and presented in a matrix form. Indeed, currents and voltages are described in terms of Fourier series and arranged in a vector form. The passive elements and the switching functions are then represented by harmonic transfer matrices. The resolution of the matrix equations leads to theoretical time and frequency expressions of the system voltages and currents. This method is applied to a closed-loop three phase AC/DC/AC PWM converter. The control loop of the converter is modeled by additional equations. The spectra of the switching functions, necessary to build the corresponding harmonic transfer matrices, are calculated through a double Fourier series decomposition. The matrix equations are solved and the results are compared to those obtained by real measurements and Matlab/Simulink simulations.
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