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Author

Matti Lehtonen

Bio: Matti Lehtonen is an academic researcher from Aalto University. The author has contributed to research in topics: Fault (power engineering) & Electric power system. The author has an hindex of 40, co-authored 694 publications receiving 8559 citations. Previous affiliations of Matti Lehtonen include Razi University & New York University.


Papers
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Proceedings ArticleDOI
16 Jul 2007
TL;DR: In this paper, the authors used the discrete wavelet transform (DWT) for the fault feature extraction corresponding to band frequency 12.5-6.25 kHz and therefore localizing this fault occurrence.
Abstract: In this paper, the initial transients in the electrical network due to arc reignitions associated with high impedance faults caused by leaning trees are extracted from phase voltages and currents. The discrete wavelet transform (DWT) is used for the fault feature extraction corresponding to band frequency 12.5- 6.25 kHz and therefore localizing this fault occurrence. The detection security is enhanced because the DWT is responded to a periodicity of the initial transients. A novel technique for the selectivity term of the faulty feeder is introduced. It is based on the power polarity, in which, this power is computed by multiplying the DWT detail coefficient of the current and voltage for each feeder. The fault due to a leaning tree occurring at different locations in an unearthed 20 kV network is simulated by ATP/EMTP and the arc model is implemented using the universal arc representation.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the energy consumption of four different passenger profiles and analyzed the resulting differences in the daily electricity consumption of the escalator, and found that passenger volumes and density during a day affect the overall energy consumption drastically.

8 citations

Journal ArticleDOI
TL;DR: In this article, the influence of lossy ground to determine the level of lightning-induced overvoltages and the corresponding risk of insulator flashovers was investigated, and a modified Gaussian cumulative distribution function was employed to estimate the probability of single-phase, two-phase and three-phase flashover of insulators based on the assumption of ground resistance close to zero.

8 citations

Proceedings ArticleDOI
06 Jun 2005
TL;DR: In this article, a novel short circuit fault location in distribution networks is presented, which computes the fault distance as reactance, based on the measurement of busbar voltages and feeding primary substation currents.
Abstract: A novel technique for short circuit fault location in distribution networks is presented. The technique computes the fault distance as reactance, based on the measurement of busbar voltages and feeding primary substation currents. The key factor is the compensation of the load currents superposed on the fault current. This leads to the accuracy, which is even better than with the previous methods, with the other difference being, that only one or two measuring device is needed, depending on the number of primary transformers at the substation.

8 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal Article
TL;DR: This book by a teacher of statistics (as well as a consultant for "experimenters") is a comprehensive study of the philosophical background for the statistical design of experiment.
Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

13,333 citations

Book
01 Jan 2009

8,216 citations

Book ChapterDOI
01 Jan 1982
TL;DR: In this article, the authors discuss leading problems linked to energy that the world is now confronting and propose some ideas concerning possible solutions, and conclude that it is necessary to pursue actively the development of coal, natural gas, and nuclear power.
Abstract: This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

2,283 citations