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.

Automatic fault management in distribution networks

Abstract: In this paper, a fully automatic computer model, called the FI-model, for distribution network fault location, fault isolation and supply restoration is presented. The model works as an integrated part of substation SCADA and medium voltage distribution network automation systems, including protective relays and AM/FM/GIS (automated mapping, facilities management and geographic information system).

DWT-Based Extraction of Residual Currents throughout Unearthed MV Networks for Detecting High Impedance Faults due to leaning Trees

Abstract: SUMMARY Modelling of a high-impedance arcing fault due to a leaning tree in medium voltage (MV) networks was experimentally verifiedand the network transients due to this fault were also investigated.Eventhough the tree had a very high resistance value, the initial transients were periodically caused by the arc reignitions after each zero-crossing. In this paper, these features are extracted from residual currents using discrete wavelet transform (DWT) to localise this fault event. The DWT performance at different measuring nodes throughout an unearthed 20kV network can be gathered at the base station using wireless sensors concept. So, the DWT is evaluated for a wide area of the network and the fault detection is confirmed by numerous DWTextractors. Due to the periodicity of arc reignitions, the initial transients are localised not only at fault starting instant but also during the fault period that will enhance the detection security. The term of locating the faulty section is determined based on ratios of the residual current amplitudes. The fault cases are simulated by ATP/EMTP and the arc model is implemented using the universal arc representation. Copyright # 2007 John Wiley & Sons, Ltd.

Comparison of artificial neural networks and conventional algorithms in ground fault distance computation

Abstract: This paper gives a comparison between an artificial neural network method and a differential equation algorithm and wavelet algorithm in transient based earth fault location in the 20 kV radial power distribution networks. The items discussed are earth fault transients. Signal pre-processing and the performance of the proposed distance estimation methods. The networks considered are either unearthed or resonant earthed. The comparison showed that the neural network algorithm was better than the conventional algorithms in the case of very low fault resistance. The mean error in fault location was about 1 km in the field tests using staged faults, which were recorded in real power systems. With higher fault resistances, the conventional algorithms worked better.

Optimal allocation of PMUs in active distribution network considering reliability of state estimation results

Abstract: Due to the lack of data in active distribution networks, employing new accurate measurement devices like phasor measurement units (PMUs) and micro-PMUs with a high reporting rate becomes an inevitable choice for the future vision of distribution systems. As a result, different algorithms have been presented to optimally place PMUs cost-effectively based on the estimation errors of the distribution state estimation (DSE) results. However, any component failure in measurement devices or communication links between sending ends and monitoring system of the distribution management system can significantly affect the DSE results. In response, this study introduces the reliability of satisfying accuracy constraints (RSACs) as an important requirement in the DSE problem. This reliability index along with the estimation errors of the DSE results are then used as two performance indices for determining the optimal number and location (configuration) of PMUs. Finally, the performance of the proposed algorithm in comparison with traditional approaches in different topologies and operating conditions of two considered ADNs is evaluated. The results proved that employing the RSACs in the optimal PMU placement problems leads to a PMU configuration with the optimum RSACs and also the cost and latency of the communication system between all configurations which have the same measurement cost and satisfy accuracy constraints of DSE results.

Operation and Design Consideration of an Ultrahigh Step-Up DC–DC Converter Featuring High Power Density

Abstract: A new dual-coupled inductor (CI) single-switch high step-up dc–dc topology featuring high power density is proposed in this study. Various capacitive power transfer methods, as well as inductive power transfer techniques, are utilized to act as a more efficient power interface between the input and the load. Three ports in the output terminal are employed to distribute the overall output voltage, diminish the voltage ripple in high-voltage gain ratios, and decrease the voltage stress on the port component. In the proposed converter, first, the voltage gain is high in lower duty cycles of the switching. Second, the stored energy of magnetizing and leakage inductances is recycled in both Cls. Third, the switch voltage spikes are alleviated. Fourth, the operation is done with no circulating current. Fifth, low-size passive components are presented. Sixth, high power density is obtained, and the voltage range is widened. Finally, a simple pulsewidth modulation (PWM) utilizing a wide control range is provided. In this study, the steady-state operation is analyzed under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM), and the performance of the converter is evaluated using comparisons with similar works. In addition, the experimental results have been provided to justify the feasibility of the design.

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.