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.

Feature Extraction ofHighImpedance Arcing Faults inCompensated MV Networks. PartI:DWT-BasedAnalysis ofPhaseQuantities

Abstract: Inthis paper, theinitial transients intheelectrical network duetoarcreignitions associated withhighimpedance faults caused byleaning trees areextracted fromphasevoltages andcurrents. TheDiscrete Wavelet Transform (DWT)isusedfor thefault feature extraction corresponding tobandfrequency 12.5- 6.25kHzandtherefore localizing this fault occurrence. The detection security isenhanced because theDWT isresponded toa periodicity oftheinitial transients. A noveltechnique forthe selectivity termofthefaulty feeder isintroduced. Itisbased onthe powerpolarity, inwhich, this poweriscomputed bymultiplying theDWT detail coefficient ofthecurrent andvoltage foreach feeder. Thefault duetoa leaning treeoccurring atdifferent locations inan unearthed 20 kV network issimulated by ATPIEMTPandthearcmodelisimplemented using theuniversal arcrepresentation.

Evaluating the Applicability of Elevators in Frequency Containment Reserves

Abstract: This paper analyzes the potential of applying elevators in power system frequency containment reserves (FCR). As an example, the study employs the Finnish FCR market structure. The markets are split into two segments: frequency containment reserves for normal operation (FCR-N) and for disturbances (FCR-D). Both of the markets have distinct minimum bid sizes and thresholds for the maximum allowed delay for activating the reserves. The paper uses a unique elevator simulator to assess the power consumption profiles of common elevator setups. Then, the elevators are aggregated into a virtual power plant (VPP) and controlled with a variety of approaches to rank the effectiveness of each control method. As a result, the paper estimates the potential contribution of elevators to a VPP-provided service as well as the adverse impact on traffic performance f or different elevator types in hourly granularity for weekdays and weekends.

Some considerations regarding the installed environment of under-ground power cables

Abstract: Cable ampacity issues have been dealt with for a long time and our own involvement, in large part to provide information of local relevance to the cable industry and power companies in Finland, is quite recent. Nevertheless, in investigating the local environmental conditions of underground HV and MV cables, a number of practical issues worth stressing have come up. Further, in acknowledgement of the difficulty in knowing the actual thermal conditions of a cable at any given point in time, a simple temperature monitoring system has been devised, based on on-line current and cable surface temperature measurements. This monitoring system involves a simple transient algorithm that enables quite accurate prediction of the conductor temperature. The conductor temperature corresponds to the maximum temperature of the insulation, and is therefore the critical parameter in determining the current rating of a power cable.

Survey of a Power Quality Measurement Campaign in Low-Voltage Grids

Abstract: With an increasing share of renewable energy generation becoming connected to distribution grids, power quality has attracted the attention of grid operators and academia. However, to obtain a realistic picture, power quality distortions caused by renewables should be superimposed on already existing emissions in grids. Measured household load data is tedious to acquire and is not publicly available. This paper presents the data from a low-voltage feeder measurement campaign and it is divided into voltage and feeder current analyses. The voltage parameters are validated as per EN 50160. The measured data includes measurements from feeders supplying single-family homes as well as one apartment building. A total of 24 weeks of 10-second mean values were recorded in the Helsinki region of Finland. Results indicate that the voltage quality is within the acceptable limits. The feeder currents show load unbalance in single-family homes and high utilisation rate of feeders supplying multiple customers.

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.