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.

Modeling and Quantification of Power System Resilience to Natural Hazards: A Case of Landslide

Abstract: Power systems are stretched across thousands of miles of diverse territories, often in remote locations, to generate and transfer the energy to geographically dispersed customers. The system is therefore subjected to a wide range of natural hazards which could potentially damage critical system components and cause interruption of electricity supply in some areas. To improve system resilience against natural hazards, management frameworks are required to identify hazardous areas and prioritize reinforcement activities in order to take the most out of the limited resources. Landslide is a natural disaster that involves the breakup and downhill flow of rock, mud, water, and anything caught in the path. It is a phenomenon frequently occurred in some parts of the world that could result in the failure of power transmission networks. Consequently, in this paper, a novel approach has been proposed that quantifies the landslide hazard, its damage to power system components, and the impacts on the overall system performance to prioritize reinforcement activities and mitigate the landslide vulnerability. The proposed approach is applied to a real power system and the obtained results are discussed in detail.

The impact of 50 Hz railroad systems on utility system unbalance

Abstract: 50 Hz railway loads, typically supplied by two phases of the transmission system, represent a possible source of the unbalance. The penetration of the unbalance is highly dependent on the stiffness of the power system and connections from the local, public network. This paper presents observations of the unbalance caused by rail loads in two various Finnish areas. Kainuu represents a rural area of a relatively weak transmission system and heavy ore trains. On the opposite, Helsinki urban area has a stiff transmission system and train loads are proportionally considerably minor. These extreme Finnish power system characteristics result in relatively high unbalance values in Kainuu and lower values in Helsinki.

Improve capacity utilization of substation transformers via distribution network reconfiguraion and load transfer

Abstract: Nowadays, the essentiality of asset management in power systems and higher utilization of resources have become more critical to keep pace with the radically growing demand of today's networks. Power transformers are amongst the most important equipments installed in power distribution systems. Therefore, this paper presents a novel methodology to improve the utilization of substation transformers. In this methodology, the transformer utilization of a two-transformer substation is increased via reconfiguration considering the single contingency policy (SCP). The online reconfiguration helps to maximize the amount of load transferred from a substation with a failed transformer to its neighboring substation. This load transfer maximization provides higher transformer capacity utilization possible. In the presented methodology, the load transfer is optimized through two hierarchical stages. In the first stage, the best configuration of the assisting substation is achieved. Then, in the second stage, load points that can be transferred from the substation with a failed transformer to its neighboring healthy substation are determined. In both of the stages, the reconfiguration problem is modeled as a mixed integer second-order cone programming problem. The IEEE 33 bus distribution network is considered as the test system and the results illustrate the effectiveness of the proposed methodology in transformer utilization improvement.

On-line PD detection for condition monitoring of covered-conductor overhead distribution networks-A literature survey

Abstract: Partial discharge (PD) measurements are universally accepted as an effective and reliable tool for on-line condition monitoring of high voltage (HV) equipment. A relatively new application is the monitoring of falling/leaning trees on the covered-conductor (CC) overhead distribution lines. Rogowski coil is used as a sensor for the detection of PDs produced due to falling trees on the CC overhead lines. This sensor is non-intrusive and superior to the conventional PD detector methods. In the next stage, this wired sensor will be converted into a wireless one. This paper gives the brief introduction to the concept and methodology of PD detection and sensor characteristics for localization of falling trees on the CC lines.

Short interruptions caused by lightning in overhead line medium voltage networks

Abstract: Lightning strokes represent a considerable cause of short interruptions in overhead line medium voltage networks The overvoltages caused by lightning can not be avoided but their influence can be limited by appropriate overvoltage protection This paper presents the results of theoretical studies about the number of short interruptions caused by lightning in various environmental circumstances The results will be compared to the fault statistics collected from Kainuun Energia In the calculations, the environmental conditions, ground flash densities and various overvoltage protection types of power distribution transformers are taken into account At the end, further research is 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.