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.

Electric Vehicle Charging Loads in Residential Areas of Apartment Houses

Abstract: Electric vehicle (EV) charging is expected to constitute a substantial part of the power demand in residential areas in the future. Its effects on the principles of distribution network planning and load profiles need to be studied. In this paper, we evaluate the feasibility of replacing the conventional cars with EVs in Finnish district heated apartment house areas. Stochastic simulation is used to combine a probabilistic charging model and electricity consumption data. We estimate the effects of uncontrolled, curtailed and price-optimized residential EV charging with different charging powers defined in the standards. The simulation results show that with 11.1 kW and 22.2 kW uncontrolled charging, the example apartment house connections would be overloaded. It is also found that the price-optimized charging should include a coordinated control logic that supports the local grid. With 1.84 kW charging, the power demand stays within the acceptable limits, but the coincidence factor increases from 0.2 to 0.63-0.93.

De-icing Schemes and Operations for Overhead Power Line Based on Shunt Capacitor Over-compensation Method

Abstract: De-icing schemes and operations for overhead power line in 10kV, 66kV and 220kV networks based on shunt capacitor over-compensation method are proposed in this paper. This novel de-icing method is based on characteristics of sinusoidal AC and theory of shunt capacitor over-compensation. By utilizing 10kV capacitor bank, which is installed as standard apparatus in substation, reactive current can be transmitted to the specific de-icing power line, which leads to over-compensation of network, and temperature of the power line will be increased. This de-icing scheme and operations are proved and verified in 10kV network by on-site experiments. Focus on characteristics and structure of power grid in China, this method is feasible to transferred and applied in 35kV, 66kV and 220kV networks.

A study for improving the energy efficiency of lifts with adjustable counterweighting

Abstract: This article presents a study of the potential energy efficiency improvement by means of adjusting the lift counterweight. The lift energy consumption in different counterweight set-ups is studied ...

Lightning Overvoltages in Electrical Power System of a Power Plant

Abstract: This paper analyzes lightning overvoltage spikes in an internal network of a large power plant. The cases considered are direct stroke to the phase conductor of the connected power transmission line and back flashover resulting from the lightning stroke to the transmission tower or shield wire. To investigate the transmitted overvoltages through transformers, high frequency models of the transformers are used. The voltage rise at the secondary side of each connected transformer at different voltage levels in the house load network of the power generation plant is analyzed. Protective measures are compared in order the study how to mitigate the transferred overvoltage at the different house load power system levels and to ensure that the impulse voltage is within the basic insulation level (BIL) of the connected equipment. Simulations using different combinations of protective surge arrestors and protective capacitors are done and recommendations on overvoltage protection are presented.

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.