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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
10 Oct 2004
TL;DR: In this article, a simple wireless sensor concept for detecting and locating faults as well as for load monitoring is presented, which is based on distributed wireless sensors that are attached to the incoming and outgoing power lines of secondary substations.
Abstract: In this paper, methods and analysis of a simple wireless sensor concept for detecting and locating faults as well as for load monitoring are presented. The concept is based on distributed wireless sensors that are attached to the incoming and outgoing power lines of secondary substations. A sensor measures only phase current characteristics of the wire it is attached to, is not synchronized to other sensors and does not need configuration of triggering levels. The main novelty of the concept is in detecting and locating faults by combining power distribution network characteristics on system level with low power sampling methods for individual sensors. This concept enables the sensor design to be simple, energy efficient and thus applicable in new installations and for retrofit purposes in both overhead and underground electrical distribution systems.

32 citations

Journal ArticleDOI
TL;DR: The impacts of two types of the FDS on distribution system reliability are compared and presented and the comparative and sensitivity case studies are conducted on a typical Finnish urban distribution network.
Abstract: Design and development of fault diagnosis schemes (FDS) for electric power distribution systems are major steps in realizing the self-healing function of a smart distribution grid. The application of the FDS in the electric power distribution systems is mainly aimed at precise detecting and locating of the deteriorated components, thereby enhancing the quality and reliability of the electric power delivered to the customers. The impacts of two types of the FDS on distribution system reliability are compared and presented in this paper. The first type is a representative of the FDS which diagnoses the deteriorated components after their failing. However, the second type is a representative of the FDS which can diagnose the failing components prior to a complete breakdown and while still in the incipient failure condition. To provide quantitative measures of the reliability impacts of these FDS, the comparative and sensitivity case studies are conducted on a typical Finnish urban distribution network.

32 citations

Journal ArticleDOI
TL;DR: In this paper, a robust framework for the temperature monitoring of power cables based on real-time current measurement only, or current measurement in conjunction with cable surface or sheath temperature measurement is presented.
Abstract: This paper introduces a robust framework for the temperature monitoring of power cables based on real-time current measurement only, or current measurement in conjunction with cable surface or sheath temperature measurement. The method is based on modeling the temperature response of a cable by summing an appropriate number of exponential functions. These functions are related to a thermal ladder circuit for installations that can be analyzed in such terms, or are mathematically fitted to numerically simulated results for those that cannot. The robustness of the method stems from the fact that exponential functions can be easily rendered into an inherently stable real-time formulation depending on the temperatures calculated at the previous increment and final conditions. The hypothetical final conditions are established at each time interval by simple steady-state calculations based on the present temperatures. This allows entry into territory that is forbidden for normal superposition methods, namely, a thermally unstable environment. Despite erroneous initial conditions, the algorithm will converge and it has the added merit of being extremely light, computationally speaking. The method provides an alternative method for transient cable rating, is inherently suited for real-time implementation, and provides a framework that can accommodate a changing thermal environment caused by, for example, such a phenomenon as moisture migration.

32 citations

Journal ArticleDOI
TL;DR: The developed framework relies on alternating direction method of multipliers (ADMM) to coordinate the operational scheduling of the agents in a distributed manner and a robust optimization technique is employed to consider the worst-case realization associated with the operation of each agent.
Abstract: Restructuring and privatization in power systems have resulted in a fundamental transition of conventional distribution systems into modern multi-agent systems. In these structures, each agent of the distribution system would independently operate its local resources. In this regard, uncertainties associated with load demands and renewable energy sources could challenge the operational scheduling conducted by each agent. Therefore, this paper aims to develop a distributed operational management for multi-agent distribution systems taking into account the uncertainties of each agent. The developed framework relies on alternating direction method of multipliers (ADMM) to coordinate the operational scheduling of the agents in a distributed manner. Moreover, a robust optimization technique is employed to consider the worst-case realization associated with the operation of each agent. Finally, the proposed framework is implemented on IEEE 37-bus network to analyze its efficacy in distributed robust operational management of distribution systems with multi-agent structures.

31 citations

Proceedings ArticleDOI
Matti Lehtonen1
16 Jun 2010
TL;DR: In this paper, the authors compared the fault rates of different line types and how these depend on line routing, i.e. line location and surroundings, and gave a summary about what is known of fault rates, both in the case of short interruptions and long interruptions.
Abstract: Society is increasingly dependent on continuous power supply. This is also taken into account in regulation models, where, in Finland, the customer's interruption costs CIC now directly affect the profit allowed for distribution system operators. This has led to the situation, where the CIC directly affects the network planning, including decisions on line types and line routing. Hence, more information is needed for detail planning, about the fault rates of different line types and how these depend on line routing, i.e. line location and surroundings. This paper gives a summary about what is known of fault rates, both in the case of short interruptions (fast and delayed reclosing) and long interruptions (permanent faults). The paper is based partly on fault statistics collected by Finnish Energy Industries and some power companies, partly on analytical studies. The core of the paper is the comparison of bare conductor overhead lines, covered conductor overhead lines, underground cables and air cables, located in forests, along the roads or in open spaces.

31 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