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.

Performance Evaluation of PD Monitoring Technique Integrated into Medium Voltage Cable Network for Smart Condition Assessment

Abstract: Online condition assessment of medium voltage (MV) cables is a valuable tool to reduce the probability of forced outages in the distribution network. Partial discharge (PD) diagnostics is being used as an efficient methodology to predict the deteriorating insulation of the power components. In this paper a comprehensive condition assessment solution is proposed for cable networks. Low cost non-intrusive devices are installed at each critical location in such a way as to monitor the entire feeder. The Direction of arrival (DOA) technique is used to monitor the PD activity. The idea of a data-base is developed to process the PD data captured by sensors distributed along the cable feeder. The performance of integrated sensors is evaluated using ATP-EMTP simulation. The proposed system can be used for both continuous and periodic monitoring. However in order to overcome the limitations of the conventional periodic and continuous monitoring, a hybrid monitoring system is proposed to be applied for the real networks.

Assessing the upward demand response potential for mitigating the wind generation curtailment: A case study

Abstract: The increased penetration of intermittent renewable generation has already resulted in spilling and it is projected that renewable energy curtailment level will continue to soar. This paper presents a framework to assess the flexibility of domestic thermal loads and Electric vehicles (EVs) charging load for power sink as a means to reduce wind energy curtailment during different times of a year. The objective of the framework is to jointly optimize the flexible loads to mitigate the curtailment thereby increasing the utilization of intermittent renewable generation. The proposed model is applied to the Finnish power system. The simulation results suggested that the proper activation of demand response (DR) is a feasible curtailment mitigation option but with an important caveat that potential subdued as the renewable penetration increases in the system.

A New Transient Impedance-Based Algorithm for Earth Fault Detection in Medium Voltage Networks

Abstract: This paper presents a new earth-fault detection algorithm for unearthed (isolated) and compensated neutral medium voltage (MV) networks. The proposed algorithm is based on capacitance calculation from transient impedance and dominant transient frequency. The Discrete Fourier Transform (DFT) method is used to determine the dominant transient frequency. The values of voltage and current earth modes are calculated in the period of the dominant transient frequency, then the transient impedance can be determined, from which we can calculate the earth capacitance. The calculated capacitance gives an indication about if the feeder is faulted or not. The algorithm is less dependent on the fault resistance and the faulted feeder parameters; it mainly depends on the background network. The network is simulated by ATP/EMTP program. Several different fault conditions are covered in the simulation process, different fault inception angles, fault locations and fault resistances.

Pollution Severity Monitoring of High Voltage Transmission Line Insulators Using Wireless Device Based on Leakage Current Bursts

Abstract: The present article describes a smart wireless online device for the severity monitoring of the contaminated insulators of high voltage transmission networks. Accordingly, the wireless developed monitor works by continuously sensing the magnitudes of the leakage current bursts and calculating its average root-mean-square (RMS) value at every second or minute as the monitor software is calibrated. Regarding, if the average of the leakage current RMS value is adjudicated by the monitor as corresponding to a probably significant scale of a power outage, the monitor transfers an alarm signal and sends a warning message to the maintenance crew members to take the action to wash the high voltage line insulators on time before the unexpected outage of the high voltage network has been occurring. The developed monitor contains the following main units: current transformer with burden resistor, Node MCU (ESP8266), solar power bank, cloud-based data storage, and smart device (Mobile or tablet). These units can be assembled to work without the need for a power source. The proposed monitor has the following merits if it is compared with the other monitoring devices: it enjoys little cost, easy of handling and calibration. It has a high degree of safety, it is an online system, and its design is simple. The developed monitor is tested in the Laboratory using insulators with different pollution layers’ conductivity and the findings show that the accuracy of the proposed monitor reached 91.66 % after carrying out 50 tests.

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.