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.

A User-centric Demand Response Framework for Residential Heating, Ventilation, and Air-conditioning Load Management

Abstract: The domestic heating, ventilation, and air-conditioning load promises a good prospect for electrical aggregators to consider it for demand response. This article presents a user-centric demand response control for scheduling the electric space heating load under a price and load uncertainty environment. The objective of the framework is to minimize a weighted sum of the expected payment, loss of comfort, and financial risk of a customer while strictly considering the end-user preferences. The household thermal behavior is modeled via an accurate two-capacity building model. The price and load uncertainty is modeled using a scenario-based stochastic programming approach. The proposed decision model is formulated as a non-linear programming problem that can be simply solved via commercially available solvers. The effectiveness of the formulation is demonstrated by applying it to a typical customer. The simulation results demonstrate that the decision mechanism allows consumers to compromise among el...

Integration of online proactive diagnostic scheme for partial discharge in distribution networks

Abstract: Partial discharge (PD) diagnostic is considered as the main concern while making condition assessment plan for medium voltage assets. PD detection and localization in multi-section (straight and branched power lines) MV network is difficult by using the conventional Time Domain Reflectometry and Time Difference of Arrival methods. It is due to interconnected cables of different lengths and properties which make the interpretation of PD signals quite complex as compared to single cable routes. This paper presents an online technique of PD localization in MV cable network. PD activity emits current pulses propagating away from the PD site. Polarity of the detected PD pulses with reference to polarity of the supply voltage determines the direction of arrival of these pulses. Comparison of the polarity of PD pulses identifies the faulty section of the overhead covered conductor line as well as the cable network. A detailed discussion has been presented to address the practical issues of sensor implementation and polarity comparison in order to ensure the accuracy of polarity based direction of arrival (DOA) assessment during field application. Evaluation of DOA is based on directionally calibrated sensors. Allocated induction sensors are employed along the feeder for integrated implementation of proposed technique in accordance with the distributed agent for improving the network reliability.

On-line PD measuring system modeling and experimental verification for covered-conductor overhead distribution lines

Abstract: In this paper, EMTP/ATP simulation environment is used to model on-line single-phase partial discharge (PD) measuring system using Rogowski coil for the monitoring of falling trees on the covered-conductor (CC) overhead distribution lines. The CC is modeled as a distributed parameters line and Rogowski coil is modeled based on its equivalent circuit as a saturable current transformer having linear magnetizing characteristics. The simulation results are compared with those obtained from the laboratory measurements. The model can be used to estimate the length of the CC line at which PDs due to falling trees can be detected; thus, deciding the number and positioning of the sensors over a particular length of the CC overhead distribution line.

Reliable Estimation for Health Index of Transformer Oil Based on Novel Combined Predictive Maintenance Techniques

Abstract: Transformer oil insulation level may be deteriorated due to electrical and thermal faults, which may lead to transformer failure and system outage. In this regard, the first part of this paper presents comprehensive maintenance for power transformers aiming to diagnose transformer faults more accurately. Specifically, it aims to identify incipient faults in power transformers using what is known as dissolved gas analysis (DGA) with a new proposed integrated method. This proposed method for DGA is implemented based on the integration among the results of five different DGA techniques; 1) conditional probability, 2) clustering, 3) Duval triangle, 4) Roger’s four ratios refined, and 5) artificial neural network. Accordingly, this proposed integrated DGA method could improve the overall accuracy by 93.6 % compared to the existing DGA techniques. In addition, the second part used for predictive maintenance is based on determining the health index for a new and an aged power transformer (66/11 kV, 40 MVA) filled with NYTRO 10XN oil by evaluating the breakdown voltage, DGA, moisture content, and acidity for the oil itself. In the breakdown voltage test, two practical types of transformer oil; transformer oil type (NYTRO 10 XN) and another type HyVolt III alongside their mixtures are evaluated and compared, where this mixture has not been reported in the literature. In addition, aged oil samples extracted from a real case study in-service transformer during operation with different aged durations; 9, 10, 11, 12, and 13 years, are tested for breakdown voltage and then compared with fresh oil samples. In the DGA task, the temperature rise test is carried out firstly on the case study, and hot dc resistance of winding is measured under different cooling systems. Considering five transformers of the same rating and oil type, the DGA was performed on oil samples extracted before and after the temperature rise test. The DGA results predicted that there was a possibility exists of local overheating. While the complementation of oil breakdown voltage technique for dielectric severity indication and temperature rise technique for thermal severity indication in addition to moisture and acidity measurements can lead to an effective maintenance plan for power transformers into the field. Hence, by using the proposed multi-criteria analysis approach (i.e., breakdown, acidity, moisture, and DGA results), the various factors are combined into a condition-based Health Index, yielding reliable estimation results compared to individual approaches.

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.