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Wyświetlanie 1-4 z 4
Tytuł:
Transients in Transformers with Non-Uniform Inductance and Capacitance Distributions
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/262695.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
distributed parameter circuits
electromagnetic transients
integro-differential equations
modeling
mutual parameters
non-uniform
power transformers
transient response
winding
Opis:
The electromagnetic transients in transformer windings exhibiting location–dependent inductances and capacitances are investigated in the time domain. Analytical functions describing this dependence are assumed and incorporated in the two integro–differential equations governing the transient voltage and current distributions. The boundary conditions are available from the source initiating the transients and the winding’s end termination. A numerical procedure is applied in order to get frequency domain solutions for the voltage and current in the form of Interpolating and Parametric Functions. The numerical Laplace inversion is then applied to these s–domain expressions. Results pertinent to transients initiated by step- and double-exponential impulse sources are presented and discussed. All possible transformers’ neutral connections are considered. The possible error introduced by neglecting either or both of the inductance and capacitance non-uniformities is addressed. Results indicate that the main error is attributed to neglecting the inductance non-uniformity, whereas the impact of the capacitance non-uniformity is relatively small. In most cases, the winding’s copper and insulation losses have a small effect on the transient response.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2017, 20, 1; 7-14
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study on the Low Frequency Transients in Power Transformers and Some Protection-Related Issues
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/1203944.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
transformer cores
inrush current
protection
transients
modeling
equivalent circuit
low frequency
nonlinear model
simulation
Opis:
This paper presents typical results for the non-linear low frequency transients following the energization of power transformers. The three operating conditions of no-load, full-load and internal faults are considered. A direct analytical procedure is applied for solving the corresponding set of differential equations describing the transformers equivalent circuit. The core representation is based on the use of curve fitting applied to their magnetization curves. The results include plots versus time for the supply current, the core flux, the magnetizing current as well as the internal induced voltage. Moreover, graphs for the hysteresis loops relating the instantaneous values of both the excitation current and the core flux are given. An approach is also presented for the numerical determination of the amplitudes of the different harmonics existing in any of these signals utilizing the corresponding equidistant samples. As examples, the DC offset as well as harmonics up to the fourth order are considered. It is shown that several useful features can be extracted from the results in both the time and harmonic domains that can assist in differentiating between overcurrents resulting from short-circuits or inrush phenomena.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2014, 17, 2; 9-16
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transformer Modelling for the Frequency and Transient Analyses, with Non-Uniform Inductance Emulating the Inter-Turn Magnetic Coupling
Autorzy:
Saied, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/262677.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
distributed parameter circuits
frequency response
modeling
power system transients
power transformers
resonance
non-uniform
Opis:
A new procedure for analyzing power transformer windings with location-dependent circuit parameters, such as the series inductance, is presented. This dependence is introduced in order to take the inter-turn mutual inductive coupling into consideration. It can be expressed either by analytical expressions or even in a tabulated form. The paper addresses both the frequency and time domain analyses. They are based on replacing the winding by an adequate number of equivalent cascade connected two-ports. In contrast to the usual practice of applying the simple medium line representation, each of these two-ports is treated as a long transmission line. Their A, B, C, D generalized circuit constants will be therefore generally location-and frequency-dependent. The analyses will be conducted in the complex s-domain. The corresponding time-domain results can then be obtained by applying a numerical inverse Laplace transform. Expressions for the winding’s input impedance with different treatments of the transformer’s neutral point will be derived for any assumed number of the equivalent two-ports. Results pertinent to the frequency characteristics including the resonance frequencies are presented. The paper also describes the winding’s transient response to the application of two standard voltage stimuli. The suggested approach is validated by its application to a case study for which an analytical closed-form solution is available. The analysis of windings exhibiting nonuniformities in more than one equivalent.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2014, 17, 1; 1-11
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multi-spark modeling of very fast transient overvoltages for the purposes of developing HV and UHV gas-insulated switchgear and of conducting insulation co-ordination studies
Autorzy:
Szewczyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/200835.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
very fast transient overvoltages
VFTO
gas insulated switchgear
GIS
disconnector switch
DS
modeling
simulations
transients
switching
mitigation
breakdown voltage
BDV
odłącznik
modelowanie
symulacje
transjenty
przełączanie
łagodzenie
rozdzielnice izolowane gazem
Opis:
Very fast transient overvoltages (VFTO) originate from steep voltage breakdowns in SF6 gas that are inherent to operation of any switching device of the gas-insulated switchgear (GIS) type. For power stations with voltage ratings exceeding 500 kV, the ratio between equipment rated- and withstand-voltage levels becomes relatively low, which causes the VFTO peak values to reach the component’s insulation withstand-voltage levels, thus becoming a design factor for high- and ultra-high voltage GIS. While well-established approach to VFTO analyses involves only single VFTO events (the so-called single-spark approach), there is often the need to analyze the entire VFTO generation process, for which the multi-spark approach to VFTO modeling is to be employed. The multi-spark approach allows one to evaluate the VFTO impact on the GIS disconnector design along with the impact of the VFTO on selection and dimensioning of the VFTO damping solutions. As the multi-spark approach to VFTO modeling is now being increasingly used in UHV GIS developments as well as for the insulation co-ordination studies of power stations, the present paper is motivated by the need to report on the VFTO multi-spark modeling approach and to lay a common ground for development works that are supported extensively with VFTO simulations. The paper presents physical assumptions and modeling concepts that are in use in such modeling works. Development of the multi-spark GIS disconnector model for VFTO simulations is presented, followed by an overview of examples of the model application for the GIS development works and for insulation co-ordination studies.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 6; 871-882
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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