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1

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.

2

A simple model of sound in enclosures with a low frequency harmonic excitation

Błażejewski A., Krzyżyński T.

Vibrations in Physical Systems

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2012

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Vol. 25

77--82

EN

In the paper the problem of a room with a sound source inside is investigated. The effect, an acoustic field inside is affected by two factors: the shape and the boundaries of the enclosure. In order to evaluate the acoustic field, modal analysis assumption has been applied to describe the room's pressure distribution. Thus, the sum over a set of the room's eigenfunctions and proper time components represents the values of the acoustic field. Eigenfunctions can be obtained by solving the Helmholtz equation for rigid walls. Time components can be determined applying Green’s theorem. This approach allows boundary conditions to be adjoined to time components and thereafter obtain a set of ordinary differential equations for each specified time component correlated with corresponding eigenfunction. Assuming a harmonic excitation, time components are harmonic as well. Therefore, the values of coefficients of each time component (i.e. the modal amplitudes) are required. Directly, one can evaluate the modal amplitudes by solving simple algebraic equations. As a result of this calculation, the finite set of eigenfunctions of an enclosure and modal amplitudes has been obtained. In this case of an additional assumption of high enough boundary impedance, the modal coupling can be neglected and consecutive formula reduction is possible. Under frequency limitation, the modal approach to a room's acoustic field modelling, involves much less computational effort than the alternative, for instance applying Finite Element Method (FEM) or Boundary Element Method (BEM).

3

Metoda analizy odkształcenia napięć w sieci elektroenergetycznej zakładu przemysłowego

Frąckowiak L., Muszyński R.

Jakość i Użytkowanie Energii Elektrycznej

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1999

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T. 5, z. 1

61-68

PL

Przedstawiono analizę odkształcenia napięć w sieci elektroenergetycznej dużego zakładu przemysłowego z wieloma źródłami harmonicznymi. Analiza dotyczy wyjątkowo niekorzystnych warunków pracy węzła sieci i z tego powodu przeprowadzona jest obliczeniowo. Obliczenia oparto na jednofazowym schemacie zastępczym. Zastosowano metodę analizy częstotliwościowej i statyczne nakładanie wpływów różnych źródeł harmonicznych. Wyniki obliczeń przedstawiono w postaci poglądowych schematów propagacji harmonicznych.

EN

In the paper the analysis of voltage distortion i the network of big industrial plant with many harmonic sources has been presented. The analysis contains the exceptionally unprofitable conditions of operation of the network nade and for that reason is made computationally. The calculations base on the one-phase equivalent diagram. The frequency method analysis and statistical superimposing of the effects of different harmonic sources are applied. There is a notion of harmonic source power introduced in the paper. The results of calculations are presented using the pictorial diagrams of harmonic propagation.