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2010 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis

Abstract [en] : This Master thesis describes a partly new procedure developed to find deviations in measured voltage and current signals. The work is an excellent example of combining theory knowledge from the university with a problem identified in the Swedish industry. A combination which stimulate technical development. The three phase signals used in this thesis work were recorded at a substation located in Stackbo, Sweden. The purpose with sorting out interesting deviations is to find connections between deviations and problems in the equipment, which can be used to detect such problems already during the measurements in connection to the substation. To sort out interesting deviations, the signals have been analyzed using Matlab and two transform methods, the Fourier transform and the wavelet transform. The new Matlab algorithms developed to analyze the signals make it possible to efficiently search through a large number of files containing signals in accordance to some efficient criteria. Setting the values for the chosen criteria is done based on typical amplitude and the noise level of the signals. The criteria can be adapted to the deviations of interest. Different types of deviations and their locations in the time scale are possible to find. For instance, notches in a signal, amplitude changes, significant deviation in the power frequency (50/60 Hz) and small regular deviations lasting for a relatively long time, can be found. Some information about how to classify the detected waveform files by the algorithms, based on the type of deviations, is also included in this thesis. This can make further development easier. Suggestions for improvements of the algorithms are mentioned at the Appendix of this Master thesis.

Place, publisher, year, edition, pages: 2010.

Keyword [en] : Physics Chemistry Maths, Mathematics, Fourier transform, wavelet transform, Matlab, algorithms, signals, substations

Keyword [sv] : Fysik, Kemi, Matematik

Identifiers: URN: urn:nbn:se:ltu:diva-48506ISRN: LTU-EX--10/160--SELocal ID: 5f40aa84-f8ad-4fd8-9b6f-0eaff70fee82OAI: diva2:1021848

Subject / course: Student thesis, at least 30 credits

Educational program: Engineering Physics, master's level

Examiners : Persson, Lars-Erik

Note: Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

Autor: Josefin, Lundqvist



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