A Model of Voltage Distribution and Change of Current in the Network Containing Unaccounted Electricity Consumption

The aim of the study is control of commercial losses in electrical grids, especially in low voltage grids, which is one of the priority lines of activities conducted by electric network companies. The complexity of solving this problem is stemming from the difficulty of exactly locating the commercial loss occurrence place under the conditions of extensively branched low and medium voltage electrical networks. Various methods are currently used to determine the commercial loss occurrence places. However, no effective methods have been created for determining the fact and place of unaccounted electricity consumption in networks under the conditions of performing remote analysis of networks based on the data from modern electricity meters used in the automated fiscal electricity metering system. These difficulties can be overcome by developing a model of voltage distribution and change of current in distribution networks of the 0.4--35 kV nominal voltage levels. A model of voltage distribution and changes of current for a network containing unaccounted electricity consumption is proposed. The effectiveness of using the proposed model has been theoretically substantiated; its applicability limits are defined, and the accuracy of the obtained results is estimated. Graphical representation of the proposed model, which is one of the electrical network digital imaging forms, can be used to analyze electrical networks for revealing if there is unaccounted electricity consumption in them. By using the proposed model of voltage distribution and change of current in the network, it is possible to represent the electrical network as a set of electrical parameters to analyze electrical networks for the presence of commercial losses.

Flux Leakage Reduction in Linear Vernier Generators Using High-Temperature Superconducting Elements

The article presents the results of studies aimed at improving the power performance indicators of linear electric generators for wave power plants by reducing the flux leakages using high-temperature superconducting (HTS) inserts placed in between the teeth. The generator design involving application of the Vernier principle for magnetic flux modulation with a translator in the form of a hollow cylinder is considered. Generators of this type are used in float wave power plants driven directly by a reciprocating float, which transmits large forces at a low motion speed. The calculations were carried out using the HTS properties modeling procedure based on representing the currents induced in a superconductor in the form of magnetic moments of these currents, which made it possible to simplify the analysis of the electromagnetic field in the generator without significant additional errors. As a result, the characteristics of the electromagnetic force longitudinal components and phase winding flux linkages versus the translator displacement have been obtained. The use of HTS inserts and a distributed winding in the stator made it possible to reduce the electromagnetic leakage losses and increase the interaction force between the stator and translator. However, since the additional outlays for the cooling system and thermal insulation of the HTS elements are commensurable with the generator cost, the obtained results on improving the power performance parameters do not allow an unambiguous statement to be made about the effectiveness of the considered technical solutions.

A Method for Calculating the Unsaturated Humid Air Flow Section Length in the Mechanical Draft Cooling Tower Sprinkler Channel

In the channels of mechanical-draft cooling tower sprinklers, a saturated air flow section may appear under certain initial conditions, the mass transfer intensity in which is limited by the steam content in the saturated air. For correctly calculating the heat and mass transfer processes in the cooling tower channel, it is necessary to have a method for determining the unsaturated air flow section length. Publications devoted to studying water cooling processes in the channels of mechanical-draft cooling tower sprinklers do not contain an assessment of the unsaturated air flow section length. A method for determining the unsaturated humid air flow section length in the mechanical-draft cooling tower sprinkler channels is proposed, which is based on the well-known criterion equations for calculating the heat transfer and mass transfer coefficients. The effect the initial air parameters have on the unsaturated air section length is studied, and graphic dependences of the unsaturated air section length are drawn up for each of the analyzed parameters. It is shown that the unsaturated humid air flow section length increases with increasing the initial air temperature. It is also found that the unsaturated air flow section length decreases with a growth in the relative air humidity. An increase in the air flow rate with a constant water flow rate leads to an increase in the unsaturated air flow section length. For the considered sprinkler channel, the saturated air region exists at an air temperature of 15°C and below, and for air temperatures above 25°C there is no saturated air flow section. It is shown that the conclusions drawn about the effect the initial air parameters have on the relative change in the unsaturated air flow section length are valid for channels of various shapes and geometric sizes. The proposed methodology and the results obtained can be used in designing mechanical-draft cooling towers and estimating their efficiency.

The Role of Vertically Integrated Structures in Industry Markets

The electric power industry is a basic sector of Russia's economy that creates necessary conditions for the activity of productive forces and life of the population. The results of electric power industry reorganization in our country are rather ambiguous. The structural changes were carried without taking the vertical integration principles in consideration, which had a significant impact on the pricing policy and investment programs. The results of studying the current state of the sector in the Russian Federation are presented, and recommendations on solving the existing problems based on the vertical integration principles are given. It is pointed out that vertically integrated companies that manage generation, distribution, transmission, and sales do not come in contradiction with the market conditions and, what is more, guarantee the power supply reliability. The relevance of this problem is stemming from the fact that the prices for electricity have a significant influence on the country economy as a whole. Under the currently existing conditions of the rapidly changing world policy, it is especially important to use vertical integration for gaining the maximum efficiency. Thus, these principles are the basis for creating an optimal market structure.

Setting up the Attribute Space of Periodic Time Dependencies for Dynamic Object Diagnostic Systems (Taking the Eye Retina as an Example)

The technology of testing dynamically and structurally similar aircraft models for flutter in subsonic wind tunnels using information and The article addresses techniques for setting up the attribute space of informative features of periodic signals recorded at the output of a dynamic object with an unknown structure in response to rectangular testing signals of different frequencies applied to the object input. The attribute space is used in developing expert systems for diagnosing the current state of an operating dynamic object. With a great variety of possible developing faults, the simplest practical techniques involving the use of characteristic points of change in the observed time dependencies yield a limited number of features with large mutual intersection domains. To expand the attribute space, it is proposed to use the expansion of input and output signals into a Fourier series for setting up a base of additional features. The proposed features characterize, depending on the testing conditions, the object’s transferring properties in the frequency domain from changes in its amplitude and phase characteristics. The test pulse frequency and duration serve as such conditions. For the convenience of comparing the object’s frequency responses variation pattern, two special procedures are used. The first procedure allows the observed time dependencies to be reduced to a single pseudo frequency of the test signals. The second procedure uses specially formed windows for subjecting individual fragments of the observed time dependencies to a spectral analysis. It is shown that, depending on the type of the frequency responses being analyzed, the techniques for their polynomial approximation, as well as integral estimates of frequency response individual domains can be useful. The polynomial approximation makes it possible to use the coefficients of the approximating polynomials as additional features, and the integration of individual characteristic domains of the frequency responses makes it possible to introduce dimensionless relative indicators that characterize the degree of change in the frequency responses depending on the experimental conditions. The considered techniques open the possibility to select additional features that can help distinguish both separate groups of faults and individual faults in operating objects. The study results are illustrated by the examples of analyzing the changes in electroretinograms that record changes in the eye retina biopotential in response to light flashes of different frequencies.

Information Literacy of a Foreign Language Teacher: An Analysis of Russian and European Professional Standards of Teachers

The introduction of information and communication technologies into the educational process began more than twenty years ago, along with the rapid spreading of computers around the world. However, not all educational institutions have supported the inclusion of information and communication technologies into the educational process for the above-mentioned quite a long period of time. Most likely, this was due to insufficient financial investments in modernization. In addition, insufficient attention was initially paid to training of teachers for working with digital technologies. At present, when information and communication competence has already been included into all international standards for teachers, it turned out that neither graduates from teacher training institutes nor teachers who have been working for already a long period of time have sufficient competencies for using digital technologies in practice. A comparative analysis of Russian and European professional standards for teachers is carried out, and the competencies they should possess are considered. Various versions of the information literacy definitions are given, which have undergone changes in the technological development process. Special attention is paid to the requirements for competencies of foreign language teachers in the field of digital technologies. The list of the currently available digital tools, including mobile devices, is discussed. The students actively use such technologies to learn languages, but to yield a really positive effect, digital tools should be integrated directly into the educational process in a professional manner. The experience of work with digital technologies gained by the teachers of the NRU MPEI Department of Foreign Languages is considered. A conclusion has been drawn, according to which a high level of information literacy enables teachers not only to change their own pedagogical methods, but also to open new horizons for their students, who, in turn, gain access to high quality education.

Heat Removal and Thermal Stabilization of High-temperature Surfaces by a Dispersed Coolant Flow

The effectiveness of stabilizing the surface temperature by a dispersed coolant flow is experimentally studied on a bench simulating energy intensive elements of thermonuclear installations A test section in which the maximum heat flux density can be obtained when being subjected to high-frequency heating was developed, manufactured, and assembled. The test section was heated using a VCh-60AV HF generator with a frequency of not lower than 30 kHz. A hydraulic nozzle with a conical insert was used as the dispersing device. Techniques for carrying out an experiment on studying a stationary heat transfer regime and for calculating thermophysical quantities were developed. The experimental data were obtained in the stationary heat transfer regime with the following range of coolant operating parameters: water pressure equal to 0.38 MPa, water mass flow rate equal to 5.35 ml/s, and induction heating power equal to 6--19 kW. Based on the data obtained, the removed heat flux density and the heat transfer coefficients were calculated for each stationary heat transfer regime. The dependences of the heat transfer coefficient on the removed heat flux density and of the removed heat flux density on the temperature difference have been obtained. High values of heat transfer coefficients and heat flux density at a relatively low coolant flow rate were achieved in the experiments.

View-independent Modeling of Lighting Systems by Local Estimations of the Monte Carlo Method

Computer-aided designing of lighting systems has been remaining of relevance for more than ten years. The most popular CAD packages for calculating lighting systems, such as DIAlux and Relux, are based on solving the radiosity equation. By using this equation, the illuminance distributions can be modeled, based on which the standardized quantitative lighting characteristics can be calculated. However, the human eye perceives brightness, not illuminance. The qualitative parameters of lighting are closely linked with the spatial-angular distribution of brightness, for calculation of which it is necessary to solve the global illumination equation. An analysis of the engineering matters concerned with designing of lighting systems points to the obvious need for a so-called view-independent calculation of lighting scenes, which means the possibility to visually represent a scene from different positions of sighting (a camera). The approach based on local estimations of the Monte Carlo method as one of efficient techniques for solving the global illumination equation is considered, and an algorithm for view-independent modeling based on the local estimations method is presented. Various algorithms for solving the problem of searching the intersection for the casted beams from a light source with the studied illumination scene are investigated.

Calculating the Electric Network Operating Parameters Taking into Account the Phase-Shifting Transformer's Variable Reactance

The aim of the work is to study the effect the variation of the phase-shifting transformer (PST) reactance has on the accuracy of calculating its control angle and the electrical network operating parameters obtained as a result of this control. The operating parameters, in particular, active power flows in the electrical circuit branches, are controlled by changing the PST angle; however, in view of the PST design features, this control entails a change of its reactance. Depending on the design features of different PST models and the control angle value, the PST reactance may be constant or vary in a significant range. In connection with a growing use of PSTs in industrially developed countries and with the fact that the first samples of this equipment have emerged in the CIS countries, including Russia, an increased attention is paid to this topic in a number of domestic and foreign publications. In particular, matters concerned with the stability of electric operation modes are considered in view of the fact that the PST reactance depends on its control angle, and the effect this dependence has on the operating parameters is estimated. The necessity of taking into account the varying PST reactance in calculating its control angle for controlling active power flows is considered for different cases. Forced redistribution of active power flows in the closed loops of an electrical network by means of a PST can be used to reduce active power losses and to maintain the required loading of the power lines for various reasons, for example, for commercial purposes or in the case of transit power flows between different countries. In view of the complexity of calculations, constant values of the PST reactance are usually assumed, but this approach is valid not for all types of PST designs. In the majority of PSTs, their reactance varies with increasing the control angle. Therefore, calculations carried out without taking this feature into account may yield a fortiori incorrect correspondence between the control angle and the transformer reactance value. In turn, an error will be introduced in the accuracy of the PST control angle calculations, as well as in the calculations of the operating parameters that should be obtained from the control action.

Determination of Marginal Power Flows Based on an Adaptive Gradual Load Increase Trajectory

The aim of the study is to develop a technique for searching an adaptive gradual load increase trajectory for power grids with a chain structure and to test this technique on the monitored 500 kV backbone grid sections. The technique for searching an adaptive gradual load increase trajectory was developed proceeding from the theoretical data about the chain structures of power grids and about the specific features of their operation modes. The voltage levels at the 500 kV backbone grid nodes and normalized phase angles across the ties included in the studied section and in the adjacent monitored sections are adopted as criteria for monitoring loss of small-signal aperiodic stability in the section under study. Special attention is paid to active power flows through the monitored adjacent sections with respect to the section under study. The proposed technique was tested on two monitored sections of the backbone 500 kV grid. The numerical analysis results have shown that under certain grid configuration and mode conditions, the marginal active power flow determined according to the proposed technique is either higher than the marginal active power flow determined using the mode change vector with the difference between the values from 54 MW to 319 MW, or lower than the marginal flow, with the difference between the values from 121 MW to 228 MW. It has been established that the difference between the values is caused by higher or lower loading of the monitored adjacent sections with respect to the section under study. Grid configuration and mode conditions has also been found in which the marginal active power flows determined according to the proposed technique and the mode change vector are almost identical with one another with the difference making about 15 MW. The subsequent algorithmic implementation of the procedure and development of the relevant software will make it possible to apply it to a larger number of monitored sections and to study various grid configuration and mode conditions for accumulating statistical data. If the software operation speed requirements in a close-to-real-time mode are satisfied, the software will be adapted to the Stability Margin Monitoring System software package. On the whole, the testing of the proposed technique for chain-shaped grids allowed us to conclude that the procedure can be used for searching an adaptive gradual loading trajectory and determining marginal active power flows in regard of small-signal aperiodic stability using the power system analysis model corresponding to the current grid configuration and mode conditions.