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.

Signal Processing Applications to Current Traveling Wave Fault Locators for EHV Transmission Networks

Abstract: Traveling waves recorders (TWRs) are used to accurately find the location of different faults in power transmission networks. These recorders are installed at few high voltage buses where current traveling waves (CTWs) can be extracted. The CTW signals' time delay of the initial wave is recoded at each TWR. In this paper, the minimum travel time of the CTW has been calculated considering Dijkstra algorithm to select the nearest TWRs to the fault point. Wavelet transform is used to find the highest energy of the details frequency band of the CTW signals. Optimum details level is extracted based on its energy content. The mean delay is calculated from the first packet of details' power profile for each TWR to be used in a double-end fault location algorithm. Time delay at the maximum power delay profile shows good results compared to the mean time delay.

Wavelet-based de-noising of partial discharge signals in MV covered-conductor networks

Abstract: Partial discharge (PD) measurements conducted in the high voltage (HV) laboratory are less affected by electromagnetic disturbances (EMD). However, on the other hand, online/on-site PD measurements are often affected by several EMD sources. Extracting low level PD signal from noisy background is a major challenge for on-line condition monitoring. The PD signals are captured in the laboratory environment and on-site measurements are simulated in MATLAB. In this paper, wavelet transform (WT) technique is proposed as a powerful tool to de-noise PD signals in medium voltage (MV) covered-conductor (CC) overhead lines. The principle of de-noising based on multi-resolution signal decomposition (MSD) is implemented. The proposed method would be implemented in a real system environment to get more stable and reliable online/onsite PD detection results for the monitoring of fallen trees on the CC distribution lines.

A dynamic fault model for a power system component

Abstract: A component of the transmission system is a subject to variety of faults. A fault obstructs the normal operation of the component and thereby the system is affected. In the worst case some customers cannot be served during the fault. These faults can be divided according to their cause and origins and the fault frequency of a single component can be modelled so that the model depends on the component itself and its environment. The scope of this paper is to present a simple model for assessing the time and location dependent fault frequency of a component. This frequency depends on season of the year, (weather) component itself (ageing, mechanics) location (environment) and constant part (operation, outsiders, unknown).

Feature Extraction of High Impedance Arcing Faults in Compensated MV Networks. Part II: DWT-Based Analysis of Residual Components

Abstract: Electrical faults due to leaning trees have been studied in [1]-[2] and it was found that the initial transients due to the associated arc reignitions are behavioral traits. These transients have been localized using the discrete wavelet transform (DWT). In this paper, these features are extracted from residual voltages using DWT. Therefore, the fault localization is carried out. The term for locating the faulty feeder is based on the polarity of a specific frequency band-power computed by multiplying the DWT detail coefficient of the residual voltage and current for each feeder. The performance of the proposed technique is getting better when the residual waveforms are utilized. Test cases provide evidence of the efficacy of the proposed technique.

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.