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Bearing damage detection via wavelet packet decomposition of stator currentEren, Levent, January 2002 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 96-99). Also available on the Internet.
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Controlling laser high-order harmonic generation using weak counter-propagating light /Voronov, Sergei Leonidovich, January 2003 (has links) (PDF)
Thesis (Ph. D.)--Brigham Young University. Dept. of Physics and Astronomy, 2003. / Includes bibliographical references (p. 127-137).
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Multi-function monitoring system for harmonic and transient study of power networks陳偉樂, Chan, Wai-lok. January 1992 (has links)
published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy
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Aukštųjų srovės harmonikų slopinimo įrenginių tyrimas / Research of current harmonics compensating devicesButkus, Gintautas 21 June 2006 (has links)
The theme of the filter of compensating devices current harmonics analyzed at present on work is actual, because concrete requirements on quality of electric energy are established. One of such requirements – size of harmonics in a feeding electric network. In industrial electric networks to which converters are connected, high harmonics on size reach 20-25 %. Special devices for eliminating harmonics are used. Condensers which are used for indemnification of reactive electric energy, do not extinguish them, therefore are projected the filter – compensatory installations, using capacity of the battery of condensers as base of the power filter. Bases of designing of the filter – compensatory devices of the parameters of semi-conductor converters of the electric power intended for normalization with a power line are considered. The purpose work of the master – the analysis of a factory electric network on the maximum harmonics and to design the filter for eliminating harmonics. The electric network has been checked up by device PQ ANALYSER. Such harmonics 3, 5, 7, 9, 11, 13 are found. The greatest on a current is third harmonic. Condensers of reactive capacity connected, network does not act on a harmonic. Compensatory installation which is made of separate filters of clearing of harmonics is designed, will strongly reduce the specified harmonics in a factory network.
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Harmonic impedance and harmonic source determination based on field measurementsNino Hernandez, Edwin Enrique Unknown Date
No description available.
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The impact of network changes on power quality and compensation device perfomance.Ngcamu, Mbulelo Busani Edmund. January 2012 (has links)
This dissertation describes the impact of changing network configuration on power quality and performance of existing compensation devices in the transmission network. The underlying theory was assessed and thereafter the Everest substation network case scenario was selected to study the above due to; the number of reconfigurations it has experienced in the past, increased capacitor bank failures and also due to the harmonics problems experienced.
The study involved the installation of harmonic current measuring instruments at Everest 132kV feeders to identify the potential sources of harmonics and to determine the dominant harmonics. A dig Silent Power Factory model was then constructed to perform various simulations in order to determine the impact of the changes done on the Everest network as well as the impact of capacitor switching on the harmonics amplification at Everest 132kV Bus-bars. The study also focussed on analysing the performance history of the capacitor banks at Everest and to determine if high harmonic amplification had an impact on capacitor bank performance.
The simulation results revealed that network reconfigurations have negatively impacted power quality at Everest. The results showed that there is also a correlation between the switching of the two 72MVAR capacitor banks and the amplification of the harmonics at Everest. The highest amplification occurred when both capacitor banks were switched in and the resonance point occurred around the 5th harmonic which coincided with the data from field measurements. There was a 61% increase in 5th harmonic impedance amplitude after the Everest network was reconfigured, for the condition when both capacitors are switched in. The lowest amplification occurred when none of the capacitor banks were switched in.
Three options were assessed to eliminate the problem of harmonics at Everest, the first one was to prohibit the switching in of both capacitors at Everest and utilise other available means around the Everest network for voltage support. The second option was to change the capacitor size, thus moving the resonance point away from the 5th harmonic. The last option was to install a harmonic filter at Everest to filter out the problematic harmonics. The first option is recommended as it has been successfully tested, can be readily implemented and is much more cost effective compared to the others. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.
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On-line digital signal processing methods for the correction of errors in high voltage power waveform measurementsHamrita, Takoi K. 12 1900 (has links)
No description available.
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Acoustic Studies on WoodHansen, Helge Johannes January 2006 (has links)
Several acoustic techniques have been used to determine elastic and damping properties of trees, logs and beams. Time of flight (TOF) measurements in the outerwood of 14-year-old Pinus radiata trees showed that pruning operations increased the outerwood stiffness by up to 25% compared with unpruned trees. However, at the most 5% to 10% of the increased stiffness can be explained by the fact that the outerwood of the pruned trees is free of knots, as TOF measurements are little affected by knots. Thus, it is not known what causes the increase of outerwood stiffness in the pruned trees. One possible explanation could be a smaller microfibril angle (MFA) in the S2 layer of the outerwood cells, which would cause a significant increase in stiffness. Thinning operations decreased the outerwood stiffness by up to 8%. In small Eucalyptus nitens and Pinus radiata logs, which had branch nodes and nodal whorls at specific locations, MOE calculations (using the resonance technique) based on different harmonics gave different results. This indicates that defects do interact with acoustic waves. Acoustic tests on laminated beams with artificial defects (holes filled with dowels) at specific locations also had a significant impact on the MOE. Moreover, it was evident that the damping ratio (evaluated from the Q- factor) of the beams increased with increasing diameter of the holes. However, it was found that holes in laminated beams decreased stiffness while branch nodes and nodal whorls increased stiffness. This shows that relatively small defects, occupying a small volume of the beam, have an impact on acoustic measurements. It is not appropriate to base the MOE calculation on a single harmonic, considering that different harmonics investigate different parts of the specimen
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A benchmarking model for harmonic distortion in a power system / Johnny RudolphRudolph, Johnny January 2011 (has links)
The present power system is loaded with sophisticated energy conversion technologies like solid state
converters. With the rapid advance in semiconductor technology, power electronics have provided
new devices that are highly efficient and reliable. These devices are inherently non-linear, which
causes the current to deviate from sinusoidal conditions. This phenomenon is known as harmonic
current distortion.
Multiple consumers are connected to the utility at the point of common coupling. Harmonic currents
are then transmitted into the distribution system by various solid state users and this could lead to
voltage distortion. Harmonic distortion is just one of the power quality fields and is not desirable in a
power system. Distortion levels could cause multiple problems in the form of additional heating,
increased power losses and even failing of sensitive equipment.
Utility companies like Eskom have power quality monitors on various points in their distribution
system. Data measurements are taken at a single point of delivery during certain time intervals and
stored on a database. Multiple harmonic measurements will not be able to describe distortion patterns
of the whole distribution system. Analysis must be done on this information to translate it to useful
managerial information.
The aim of this project is to develop a benchmarking methodology that could aid the supply industry
with useful information to effectively manage harmonic distortion in a distribution system. The
methodology will implement distortion indexes set forth by the Electrical Power Research Institute
[3], which will describe distortion levels in a qualitative and quantitative way. Harmonic
measurements of the past two years will be used to test the methodology. The information is obtained
from Eskom’s database and will benchmark the North-West Province distribution network [40]. This
proposed methodology will aim to aid institutions like NERSA to establish a reliable power quality
management system. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2012
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Novel composites for nonlinear opticsHameed-Muhammed, Muhammed Subhi January 1999 (has links)
No description available.
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