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 …

I and i

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

The Design and Analysis of Experiments

计量经济分析 = Econometric analysis

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.

World energy outlook

Introduction to stochastic programming

Partial discharge (PD) detection and localization in medium voltage (MV) cables connected in branched network configurations, is difficult by using the conventional methods. It is due to interconnected cables of different lengths and impedance which make the interpretation of PD signals quite complex as compared to single cable routes. This paper presents an online technique of PD localization for branched cable network. PD activity emits current pulses propagating away from the discharge location. Polarity of the detected PD pulses with reference to polarity of the supply voltage can determine the direction of arrival of PD pulses. Comparison of the polarity of PD pulses captured at different cable branches identifies the faulty section of the cable network. Evaluation of direction of arrival is based on directionally calibrated installed sensor. In this paper induction sensors are employed for implementation of the proposed technique. Integration of the proposed technique over a wider network can be very useful as an efficient diagnostic tool for improving the reliability of power supply.

Online partial discharge diagnostics in medium voltage branched cable networks

This paper describes the characteristics of the earth faults and related disturbances, recorded in medium voltage overhead distribution networks during the years 1998-1999. Altogether 316 real cases were analyzed. The use of subharmonic oscillation and harmonic distortion was investigated, as a means of anticipating of faults. Arcing faults made up at least half of all the disturbances, and were especially predominant in the unearthed network. Fault resistances reached their minimum values near the beginning of the disturbances. The maximum currents that allowed for autoextinction in the unearthed network were comparatively small.

Earth faults and related disturbances in distribution networks

Proliferation of photovoltaic (PV) panels may cause voltage increases in low voltage (LV) distribution feeders. This issue confines PV hosting capacity of the feeders. To overcome this issue and enable higher PV hosting capacity, a model to manage the operation cycles of the domestic electric water heater and heating, ventilation, and air conditioning loads in order to avoid the voltage rise, thereby increasing PV hosting capacity in LV feeders is presented in this study. The model respects users' thermal comfort by setting the associated temperatures within allowed ranges. To preserve customers' privacy, the presented model is then decomposed into a master problem and several sub-problems using the Dantzig-Wolfe decomposition algorithm. Thereafter, an effective scheme is designed to solve the decomposed problem in a distributed fashion. In the scheme, the master problem is solved by the system-wide module and the sub-problems are solved by house-wide modules. The problems are all in linear format which can be easily solved with affordable computation. Importantly, the proposed model can reach the optimal solution while minimal data is shared between houses and control centre.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-rpg.2019.0159

Distributed load management scheme to increase PV hosting capacity in LV feeders

Lightning storms may only last some hours, but the number of faults during these storms can represent a considerable share of the annual disturbances. In this paper, six identified lightning storms were the main interest. In general, single-phase earth faults are the most typical fault type. However, in the lightning storms we researched, short circuits represented the majority of faults. The majority of faults, both during lightning storms and in normal conditions, are cleared by high-speed auto reclosure. In addition, it was observed that during lightning storms coincident faults and fault types that develop into another fault type before the opening of the circuit breaker occurred repeatedly. When observing the influence of overvoltage protection type on faults, the results encourage the use of surge arresters.

Measured faults during lightning storms

Nowadays, strategies to cope with environmental issues play a crucial role in the development of planning methodologies for electric distribution networks (EDNs). The primary goal of these methodologies is to find the equilibrium point, for which the EDN provides a high-quality service with the most environmentally-committed operation. Based on this fact, an alternative strategic approach for short-term EDN planning is presented. This decision-making scheme is based on classical investment actions to enhance the EDN performance in which the investment and operating costs, as well as the carbon tax surpluses, are minimised simultaneously. Unlike the traditional short-term planning methods and to explore a more accurate approach, the electricity demand is represented by the voltage-dependent exponential load model. By using this representation, substantial benefits related to energy saving can be achieved. To validate the proposed planning scheme, several test cases considering constant power demand and voltage-dependent representation are widely studied on a 135-node distribution network. Additionally, the scalability of the proposed planning scheme is studied by using two medium distribution networks of 42- and 417-node. Numerical results confirm the robustness and applicability of the presented approach as an appropriate way of promoting to an efficient and low carbon tax surplus network.

/pdf/voltage-dependent-load-model-based-short-term-distribution-38ol1iuzmf.pdf

Matti Lehtonen

Papers

Online partial discharge diagnostics in medium voltage branched cable networks

Earth faults and related disturbances in distribution networks

Distributed load management scheme to increase PV hosting capacity in LV feeders

Measured faults during lightning storms

Voltage-dependent load model-based short-term distribution network planning considering carbon tax surplus