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.

Coordination strategies for distributed resources as frequency containment reserves

Abstract: Distributed resources are increasingly considered to be potential reserves for frequency control but some of these resources, such as demand response (DR) and battery energy storage systems (BESS), are limited in energy capacity. This may complicate their utilization in a frequency containment process if the power system does not have a proper strategy to coordinate and maintain the system frequency. In this paper, we examine the resources provided by refrigerators and BESS, and argue that with proper frequency coordination the contribution of these resources to frequency containment reserves (FCR) can be improved. Two distinctive cases are compared: one where the power system has an automatic process for frequency restoration and the other where such a process does not exist. In the latter case, the resources need to cope with the long lasting frequency deviations locally. The study is based on the simulation of different control strategies and the frequency measured in the Nordic power system. The results indicate that a proper frequency restoration strategy can enhance the potential of distributed resources as FCR.

Evaluation of chirp detector-based travelling wave localization of earth faults in MV networks

Abstract: In this paper, a chirp detector of the current waveforms is evaluated for locating the earth faults in unearthed MV networks where it is used to precisely localize the travelling wave arrival times created by the fault occurrence. Chirp modulation, or linear frequency modulation employs sinusoidal waveforms whose instantaneous frequency increases or decreases linearly over time. These waveforms are commonly referred to as linear chirps or simply chirps. Earth faults in unearthed MV networks will spark a chirp signal which is starting at a high frequency then gradually decreasing to a small frequency. A simple chirp detector is used to demodulate the frequency modulated waveform resulting in a signal peak which is used to locate the fault by a time of arrival method. The evaluation is carried out considering practical modelling of current transformer (CT) where the CT is modelled covering its high frequency characteristics. Also, the network noises are added to the simulated current waveforms. The simulation is performed in the ATP/EMTP program where it is pre-processed using ATPDraw. (5 pages)

Optimal UPFC based on Genetics Algorithm to improve the steady-state performance of HELENSÄHKÖVERKKO OY 110 KV NETWORK at increasing the loading pattern

Abstract: Flexible Alternating Current Transmission Systems (FACTS) devices represent very high efficient tools for controlling the operations and enhancing the performances of the electrical power network. Unified Power Flow Controller (UPFC) is considered as the most powerful member of the FACTS family, where it has both shunt and series controller inside its frame. This option gives to UPFC the power to control the voltage profile and the transmission lines flow simultaneously. In this paper, we use the Genetics Algorithm (GA) to find the optimal location and the optimal settings of UPFC to improve the performance of the power system specially solving the transmission lines overloading during normal operation and configuration at increasing the loading conditions. This procedure is proposed to be applied on Helsinki HELENSAHKOVERKKO OY 110 KV NETWORK until the operating conditions of Year 2020. To show the validity of the technique, it will be tested on the IEEE 6-bus system.

Enhancing the Protective Performance of Surge Arresters against Indirect Lightning Strikes via an Inductor-Based Filter

Abstract: Preventing the medium voltage (MV) transformer fault by protecting transformers against indirect lightning strikes plays a crucial role in enhancing the continuous service to electricity consumers. Surge arresters, if selected properly, are efficient devices in providing adequate protection for MV transformers against transient overvoltage impulses while preventing unwanted service interruptions. However, compared to other protective devices such as the spark gap, their prices are relatively high. The higher the surge arrester rating and energy absorption capacity are, the higher the prices go. This paper proposes an inductor-based filter to limit the energy pushed into the surge arrester, and consequently to prevent any unwanted failure. An energy-controlled switch is proposed to simulate the fault of the surge arrester. Surge arresters with different ratings, e.g., 12 kV, 18 kV, 24 kV, 30 kV, 36 kV, and 42 kV with two different classes of energy, namely, type a and type b, are tested under different indirect lightning impulses such as 100 kV, 125 kV, 150 kV, 175 kV, 200 kV, 250 kV, 300 kV, and 500 kV. Furthermore, these surge arresters are equipped with different filter sizes of 100 μH, 250 μH, 500 μH, and 1 mH. Results prove that equipping a surge arrester with a proper filter size enhances the performance of the surge arrester significantly such that a high rating and somewhat expensive surge arrester can be replaced by a low rating and cheap surge arrester while providing similar or even better protective performance for MV transformers. Therefore, such configurations not only enhance the protective capability of surge arrester, but also reduce the planning and operating costs of MV networks.

Customer Interruption Cost Estimations for Distribution System Operators in Finland

Abstract: Basic There is increasing attention on the estimation of the customer interruption costs. The existing studies adopt indirect analytical methods, customer surveys and case studies to evaluate these costs. This paper makes use of two existing cost estimation techniques and suggests a simple and straightforward methodology which will provide sound and reliable estimations in an objective manner by relying solely on publicly available analytical data, The study is based on 78 Finnish Distribution System Operators' 2016 energy and reliability data. In addition, the standard customer compensation scheme in Finland is briefed and the results are compared with the power interruption cost estimations.

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.