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.

Modelling of a voltage transformer for transients

Abstract: This paper presents the modelling of a 110 kV inductive voltage transformer for transients. The inductive voltage transformer ratio typically changes a lot for frequencies up to the 50th harmonic. To make a good model in this frequency range is the main task of this paper. A traditional lumped, linear model that includes capacitances gives satisfactory results. A new method of model capacitance estimation has been developed and is presented. The capacitance estimation is based on a real transformer measurement and recalculations. The model response was tested in EMTP/ATP and compared to the real transformer. This method can be used for simple and accurate modelling of inductive voltage transformers up to 10 kHz.

Cyclone Dagmar of 2011 and its impacts in Finland

Abstract: The increasing frequency of the natural disasters during the last decade and their severe impacts on the electric power arose debate and led questioning the electric power reliability of the European countries. The Cyclone Dagmar of 2011, or locally known as Tapani storm, was a shocking event for all Scandinavia in terms of its impacts on the electricity supply and the related services. Although Finland had been thought to be enjoying highly reliable electric power, after 2011 the authorities started to go through radical changes to improve the supply security of the country and the Finnish Ministry of Employment and the Economy introduced a 15-year plan to avoid such undesirable outcomes of the possible natural disasters that might occur in the future. This paper summarizes and presents the events that were caused by the storm, and the storm recovery efforts spent after the incident.

Multistage Expansion Co-Planning of Integrated Natural Gas and Electricity Distribution Systems

Abstract: This paper focuses on expansion co-planning studies of natural gas and electricity distribution systems. The aim is to develop a mixed-integer linear programming (MILP) model for such problems to guarantee the finite convergence to optimality. To this end, at first the interconnection of electricity and natural gas networks at demand nodes is modelled by the concept of energy hub (EH). Then, mathematical model of expansion studies associated with the natural gas, electricity and EHs are extracted. The optimization models of these three expansion studies incorporate investment and operation costs. Based on these separate planning problems, which are all in the form of mixed-integer nonlinear programming (MINLP), joint expansion model of multi-carrier energy distribution system is attained and linearized to form a MILP optimization formulation. The presented optimization framework is illustratively applied to an energy distribution network and the results are discussed.

I and i

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 …

The Design and Analysis of Experiments

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

World energy outlook

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.