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.

Operation evaluation of DWT-based earth fault detection in unearthed MV networks

Abstract: A novel selectivity technique to estimate the faulty feeder in MV networks was introduced in [1]. This technique depended on the directionality of discrete wavelet transform (DWT) detail coefficient of a residual current of each feeder with respect to the DWT detail coefficient of the residual voltage. The algorithm efficacy has been examined with high impedance arcing fault due to leaning trees. In this paper, the algorithm performance is tested with resistance earth faults over a wide range of the fault resistance values (1 mOmega to 100 kOmega) as well as concerning practical fault cases such as arcing faults. The fault cases occurring at different locations in an unearthed 20 kV network are simulated by ATP/EMTP. Test cases confirm the efficacy of the proposed technique.

Practices to improve the annual elevator energy consumption estimates and measurements

Abstract: Elevators form a crucial service of a functioning modern society, and the amount of installed units will continue to rise with increasing urbanization. Consequently, the energy efficiency of elevators has begun to attract more attention. However, elevators are rarely being monitored with energy meters, and the actual energy consumption of these devices is therefore commonly based on estimates. This paper provides useful measurement data from a mid-rise office building and analyzes the gathered readings against two energy efficiency classification schemes: the VDI 4707-1 guideline and the ISO 25745-2 standard. This study presents key points for improving the annual consumption estimates provided by these two commonly applied schemes. Furthermore, this paper identifies challenges in the determination of actual energy consumption based on kWh meter readings. The findings of this paper can be applied at any site to reduce errors in the energy consumption modeling of elevators. The results highlight the significance of correctly interpreting the methods of the classification schemes and knowing the total amount of starts of an elevator or an elevator group. Most importantly, the paper finds the elevator usage and consumption to depend heavily on the installed elevator technology as well as the people flow characteristics of the building.

Agent based bidding architecture in electricity markets for EVs as V2G and G2V

Abstract: Due to the expected high penetration of intermittent renewable energy sources in power grid, such as solar and wind, the issue of matching demand and supply would become more critical. In order to address the issue, this paper investigates the potential of Electric Vehicles (EVs) for the short term power imbalances in smart grid. This paper proposes a simple bidding algorithm for energy market for EV's participation in V2G and G2V. The key finding is the initial cost of the EV battery which could make EV as a market player for maintaining short term balances.

Limiting the number of the most severe voltage sags in rural medium voltage networks

Abstract: In Finland during summer time, lightning may cause a considerably high number of short interruptions and voltage sags. In case of lightning, the overvoltage protection of power distribution transformers has an important role. In case of special concern of voltage sags, the means to limit the short circuit faults causing voltage sags should be focused to the neighbourhood of the primary (110/20 kV) substation. To contribute this matter, this paper presents results of a study where spark gaps were replaced with externally gapped metal-oxide surge arresters near the primary substation. As well the theoretical studies as measurement results encourage to carry on with such investments.

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.