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The insulation of an oil-filled transformer is based on materials of organic origin - oil and wood pulp. The state of insulation is a key factor in the reliable operation of a power equipment, and much attention is paid to the insulation state assessment by researchers. To assess the cellulose insulation state, indicators such as the degree of polymerization and paper moisture are deter-mined. The existing methods for determining the moisture content and the degree of polymeriza-tion of a paper insulation have disadvantages, as they require a complex process of sampling the insulation, which is a time-consuming operation. The purpose of the work is to develop new methods for determining the moisture content and the degree of polymerization of the paper in-sulation of a power transformer. This goal is achieved by obtaining the reflection spectra of the paper insulation samples and constructing two correlation lines to determine the degree of polymerization and humidity. The most significant result of the article is the establishment of the dependence of the reflection coefficient of the paper on the concentration of water exceeding 4% and the position of the minimum in the reflection spectrum of paper insulation on the degree of polymerization. The significance of the obtained results lies in the fact that the optical method for determining the moisture content and the degree of polymerization of paper insulation using the constructed correlation lines is highly accurate and does not require the use of additional re-agents and complex calculations.

Modern energy systems are often used as a medium for information transmission, including confidential information, which makes relevant the task of ensuring its security, which today is solved using not only cryptographic but also steganographic means that ensure concealment of the very fact of confidential information transmission. The steganographic method with code control of the additional information embedding possesses practical important qualities, but in its original form requires the presence of a container for successful information extraction, which is not always desirable in practice, while the known modification of this steganographic method allows blind decoding is characterized by an insufficient level of resistance to attacks against the embedded message. The purpose of this paper is to improve the efficiency of the steganographic method with code control of the additional information embedding and blind decoding. This purpose was achieved by identifying two factors that determine the occurrence of errors during blind decoding of additional information in the steganographic method with code control: variation of sub-blocks, and errors caused by attacks against the embedded message. We pro-pose the theoretical and practical rationale for codewords that provide the best level of re-sistance to both factors. The most significant result of the paper is a reduction in the number of decoding errors of the steganographic method with code control of the additional information embedding and blind decoding by 12.01% compared to the result known in the literature through a reasonable choice of codewords used to embed the additional information.

The paper presents the results of the study of a two-stage procedure for selecting a reference object in the current image formed by a correlation-extreme system used for autonomous navigation of unmanned aerial vehicles. The aim of this paper is to theoretically evaluate the probability of selecting low-dimensional low-contrast objects in the segmented current image according to the proposed two-stage procedure. To achieve this goal, the problem of segmentation of images of the sighting surface and subsequent selection of the reference object in the presence of heterogeneous objects differing in brightness and area characteristics is solved. The most significant result is the justification of application of two-stage procedure of selection of the reference object in the current image by brightness and area parameters using the set thresholds. The significance of the obtained results consists in establishing the dependence of the probability of correct selection of the reference object on the noise level of the current images. It is shown that the probability of correct selection of the object in the image is a function of the threshold value and can be maximised by choosing its value. This approach allows to consider the influence of various factors leading to image noise on the quality of images formed by the navigation system. It is shown that when noise distorts more than 31% of the image pixels, the proposed two-stage procedure allows to ensure the selection of the reference object in the image with a probability not lower than 0.9.

The paper deals with a capacity of high-voltage cable line made of three single-core cross-linked polyethylene insulated power cables. We consider three cases. First is a single-point bonded cable system when no magnetic field shielding technique is implemented and the capacity achieves maximum values. Second is a solidly bonded cable system when a thermal effect of induced shield currents causes a capacity reduction. The third case under study is a single-point bonded cable system covered by the passive loop. The passive loop mitigates the cable line magnetic field as well as the solidly bonding does, but also the thermal effect of passive loop currents reduces the capacity. The goal of the paper is to evaluate the relative change of cable line capacity when implementing magnetic field shielding techniques comparably to unshielded case. To achieve the goal we use a standard IEC 60287 when calculating the cable line capacity in the first and the second cases, and a thermal field simulation in the third case. The capacity is evaluated by successive approximations. Iterations are stopped when the conductor reaches the maximum operating temperature. We show that the increase in cable spacing does not guarantee the capacity increase when the solid bonding of cable shields or the passive loop is used. The most significant result is the substantiation of the advantages of passive loop, which provides the greater capacity in comparison with solid bonding at equivalent magnetic field shielding efficiencies. The obtained results can be used when choosing the type of bonding and the technique of cable line magnetic field mitigation.

This paper is devoted to the development of a decentralized control system design method with improved robustness, applicable to distillation columns control problem. The aim is attained by solving the following tasks: selection of representative models of columns; development of an effective transfer function identification algorithm; development of a decentralized controller design algorithm, which takes into account the cross-links impact; verification of the developed method for the selected models of columns. The most important result is the developed design method, which includes two algorithms. The first algorithm can be used to identify simplified models of the effective transfer functions. The second algorithm makes it possible to design a decentralized control system based on the ratio between the diagonals of the original model and effective transfer functions. Modified PI controller is used. The achievement of the distillation column control system robustness to the synchronous technologically conditioned deviation of the model parameters by up to three hundred percent of the nominal value is the paper signifi-cant result. The digital implementation of the designed controllers is simple. The analysis of the literature shows that none of the previously proposed methods for designing decentralized au-tomatic control systems solved such a problem. The efficiency of the developed algorithms is illustrated using the known models of dynamics of distillation columns. The analysis of limita-tions of the method as well as its significant differences to the Biggest Log Tuning and H∞ loop shaping methods is presented.

The paper aim was to study the normal functioning modes of consumers power supply by the distribution network, taking into account the electricity production using wind turbines, as well as to develop recommendations that allow optimizing power consumption modes. The goal was achieved by analyzing the initial information on the network section topology, the technical characteristics of linear and transformer equipment, as well as consumption and generation profiles. The most significant result of the paper was the determination of the fact that the connection of wind turbines according to the “install and forget” principle without prior justification of both connection place and wind turbine capacity often leads to significant change in the operating characteristics and additional technical losses of active power. In this case, the main part of the losses falls on power lines. The significance of the obtained results lies in the fact that the main problems, associated with the coordination of the operating modes of distributed generation facilities and load, were identified and possible technical solutions were proposed to improve the situation. Based on the obtained results it is possible to conclude that when connecting a wind turbine to a distribution network, it is necessary to take into account both the capacity and the installation location of the equipment, which significantly change the values of the operating parameters of electrical networks. It has been shown that use of energy storage devices, as well as the network reconstruction, can make it possible to minimize active power losses and carry out balance of regimes.

The use of municipal solid waste as a raw material for alternative fuel is a promising direction for waste recycling and substitution of solid fossil fuels. Therefore, selecting of fuel composition and studying of its properties is an urgent task. The aim of this work is thermal characteristics analysis of the combustible components of municipal solid waste, which are the most common in Ukraine, for further selection of a fuel composition that will satisfy the consumer's requirements. The goal is achieved by studying the thermal destruction of samples by thermogravimetry and differential thermal analysis when materials are heated to 1000 ºС in the presence of air oxygen. Paper, cardboard, plastic, biodegradable film, textiles, leather, wood were investigated in this work. The most important results are the received data on the characteristic temperatures of destruction stages, content of water, organic and mineral substances, ash, as well as the calculated values of rate and conditional thermal effect of decomposition of organic substances. Strong formation of gaseous substances was registered for samples of polyethylene and biodegradable film, polyethylene terephthalate and cotton fabric. These features should be considered in the technologies of production and combustion of fuel. The significance of the results also lies in the fact that it is recommended to use data on the thermal stability of materials in order to prevent their ignition during drying when developing fuel production technology. In addition, the calculated values of the conditional thermal effect made it possible to evaluate the thermal characteristics of the studied materials as components of solid alternative fuels.

The aim of the paper is to research possibility to use a "hexagon" scheme static frequency converter as controlled intersystem link for two parallel operating power systems with different operating frequencies, or standards for frequency stabilization. The paper aims to study the transformer device operating characteristics that implements the output voltage phase circular rotation principle relative to the input voltage and controlled by power electronics. This goal is achieved through the elaborated "rough" device control strategy, which made it possible to provide controlled AC intersystem link of asynchronous power systems without the use of additional harmonic filters and dampers. Two sectioning modes of adjusting windings were used to apply 24 and 48 position laws of the converter "fine" control. The most significant results are the new technical solution of the frequency converter, as well as the "rough" control strategy. To assess the conversion quality, indicators were used that characterize the degree of stability of the transmitted power and the harmonic distortion of the current. The computational experiments results have shown the effectiveness of the proposed "rough" control strategy. It is proved that 48-position sectioning of the "fine" regulation winding can significantly improve the quality of conversion compare to 24-position. The obtained results significance is that developed technical solution provides acceptable indicators of the frequency conversion quality and transmitted active power stability. In addition, the use of the proposed converter technical solution can significantly reduce the number of windings and control means compare to previously ones studied by the authors.

This paper presents the results of a study on optimising the feed stream pressure of the Mixed Fluid Cascade natural gas liquefaction cycle. The objective is to optimise the pressure of the feed stream to distribute heat effectively over the cooling stages and reduce the energy cost of the cycle. To achieve the goal, the following tasks have been done: constructing the mathemati-cal model of the cycle, performing the calculation experiment for different values of the feed stream pressure to determine energy characteristic values, and determining the optimal values of feed stream pressure. The flow characteristics of the working substances in the cycle are deter-mined based on the Peng–Robinson–Stryjek–Vera equations of state and Benedict–Webb–Rubin. The mass flow of the working substance is calculated for each cycle's stage heat load, at both constant and different values of the working point temperatures. The distribution of heat load for liquefying 1 kg of natural gas by stages is displayed, and achievable working point tem-peratures of the feed flow are determined. The energy consumed by the compressor units and the amount of compression heat dissipated are calculated. The study's main finding is that the optimal feed pressure in the Mixed Fluid Cascade cycle is higher than the standard pressure. The significance of the obtained results lies in the significant reduction of energy costs of the Mixed Fluid Cascade cycle at a feed stream pressure of 13 MPa.

A significant part of thermal energy is lost precisely during its transportation. By increasing the efficiency of thermal insulation of pipelines, it is possible to reduce significantly heat loss around the world. The purpose of the paper is to develop and validate methods for increasing the efficiency of thermal insulation of pipelines by determining its optimal location. This purpose has been achieved by applying of a modified method for studying the process of heat loss, taking into account the radiation component, to calculate the heat loss and surface temperature of the thermal insulation with different spatial arrangements. For comparison, we analysed three options for the heat loss of pipe with a different spatial arrangement of thermal insulation coated with an aluminium reflective film facing outward, facing inward and in both directions. Comparison of these variants showed that it had been advisable to insulate the pipelines by installing an insulation layer coated with an aluminium reflective film facing in both directions. The main result of paper has been the proposed method for calculating of heat losses, which could be used in the design of thermal insulation of pipelines and the obtained data confirming the correspondence of theoretical calculations to actual values of the surface temperature of thermal insulation taking into account its various spatial arrangements. The importance of the results of the work lies in the possibility of using this technique to assess the effectiveness of thermal insulation of pipelines and determine the best solutions for its spatial location.

The past decade has been characterized by considerable increase of the penetration level of so-lar photovoltaic systems in energy systems throughout the world. At the same time, solar irradi-ance has an intermittent nature. Thus, the efficient management of existing and new solar pho-tovoltaic systems requires an accurate forecasting system of solar irradiance. The purpose of the paper is to develop and validate a long-term forecasting model for solar irradiance. This purpose is achieved by applying of clustering method and standard mathematical statistics. The modeling includes pre-processing of historical data used for forecasting and post-processing of the types of days resulted from the clustering analysis. Historical data include solar irradiance and sky coverage by clouds. Pre-processing supposes bi-normalization of the solar irradiance in time and amplitude, as well as clustering, and post-processing supposes denormalization to get the actual values. Error metrics and confusion matrix indices have been used to assess the accuracy of the proposed forecasting method. Four different model variants have been considered, which differ by pre-processing approach of initial data. The comparison of these model variants shows that for better accuracy it is required to use seasonality aspects of solar irradiance. The main result of paper is the created model, which can be used for the solar irradiance forecast with acceptable accuracy for this type of forecasting and for generating of the types of days for different annual scenarios. The importance of paper results consists in the possibility of using of these scenarios for feasibility assessment of the solar photovoltaic system and identifying of the best solutions for their integration in the energy system.

The purpose of the paper is to form a method for finding the optimal structure of the power network. For the basic criteria of the required method the maximum simplicity, versatility and objec-tivity are assumed. The properties of existing power grids of various countries and the methods of their analysis and design were analyzed. The research is based on the method of relative comparative assessments. In the paper a set of particular optimization criteria was substantiated, which objectively characterize the power network. These criteria include a complex assessment of the length, an energy assessment, a wires mass assessment and a reliability assessment. A complex length assessment con-sists of total length assessment of power lines and assessment of total lengths ratio of power lines to conventionally low and high voltages. The overall reliability coefficient of the power supply was pro-posed to use as a reliability criterion. This factor conventionally represents the level of duplication of power supply in terms of free power and transmission capacity of the power lines. The algorithm for determining the values of partial criteria was considered. The partial optimization criteria were com-bined using the complex additive criterion. The example of finding the optimal structure of a local dis-tribution power network was given. As variants for the structures of the power network, the schemes of a looped, a trunk passage, a trunk-radial and a trunk with branch were used. In accordance with the method of relative comparative assessments, it was found, that the looped type is optimal.

Society is becoming increasingly dependent on energy. It is a stimulating factor for economic growth and technological change, but also the most significant limiting factor. The analysis of research trends on energy is of great importance because it provides a picture of the development directions of the future. The goal of the paper is to evaluate the performance and tendencies of researches on energy in the World, Eastern Europe region and in the Republic of Moldova. This goal is achieved by using bibliometric methods. Bibliometrics has become standard method for measuring the impact of research, which is accepted as a valid way of ranking scientific performance and tendencies. The novelty of the work consists in the wider geographical and chronological coverage of the study in comparison with similar studies, as well as that the analysis was carried out based on data extracted from two international and one national databases: Scopus Elsevier, Web of Science Core Collection and National Bibliometric Instrument. It was revealed that on global, regional and national levels the number of papers on energy increases quicker than the total number of publications. There is also a growth of the share of publications on energy from total number of documents on global, regional and national levels. The contribution of the Eastern Europe in the global information flow on energy increases slowly but stable. Lower speed of increase of the contribution of the Republic of Moldova in the regional (EE) information flow on energy is detected.

In this paper, the movement of a gas-fluid flow in a plane channel with an oscillating wall was investigated. The aim of the research is to increase the efficiency of separation equipment by imposing the vibration impact on a gas-liquid flow. This purpose was achieved by applying the phenomenon of selective coagulation of a dropping liquid. The novelty of the proposed ap-proach concerns creating the mathematical model for determination of analytical dependences between the efficiency of the hydromechanical process and initial parameters of the separation device. As a result, quantitatively and qualitatively sufficient approximations for the scalar pres-sure and vector velocity fields were obtained with a permissible relative error in comparison with the results of numerical simulation. The presence of biharmonic fluctuation of particles was proved; besides, related dependencies for the calculation of vibration characteristics were ob-tained. Additionally, the paper presents the dependencies for identifying a range of thickness for a near-wall area. The system of dimensionless criteria was proposed for determining flow modes and relative trajectories of liquid droplets in a gas-fluid flow. The numerical simulation approach and related methodology of engineering calculations were proposed on the example of a plane channel of the separation device. Finally, the distance between adjacent zones of the pressure minimum was determined. As a result, it was found that this distance is equal to the wavelength of the vibrating impact to the flow that is an initial justification of further coagulation process of liquid droplets in a gas-liquid flow in a separation device.

The purpose of this work is to determine the heat transfer coefficient of translucent fences, considering the number of storeys of buildings, climatic factors, such as wind velocity and outdoor temperature. To achieve this goal, the following tasks were solved: analysis of heat transfer in translucent enclosures as a quasi-stationary process; analysis of heat transfer processes in translucent barriers, which are a combination of solid transparent plates and air gaps connected by a frame structure; determination of the heat transfer coefficient on the glass surface depending on climatic factors and the radiant component. The most important result is the empirical dependence of the heat transfer coefficient on the outer surface of the window block on the Reynolds criterion, the dependences for determining the heat transfer coefficient of window blocks are improved, considering climatic parameters. The heat transfer coefficient of the window block as a whole is presented in the form of analytical ratios, considering the location of the building and its height, changes in wind velocity and outdoor temperature. This methodology was tested on the example of a civil administrative building, for which the heat transfer coefficients of window structures of non-standard series were evaluated. The significance of the research results lies in the possibility of using the obtained dependencies to assess the thermal characteristics of window structures of non-standard shapes. The dependences of the heat transfer coefficient on wind speed and outside air temperature given in the paper can be used in the energy audit of buildings.

In this paper, we consider the problems related to measuring and analyzing the characteristics of partial discharges which are the main instrument for oil-filled high-voltage electrical equipment diagnosing. The experiments on recording of partial discharges in transformer oil have been carried out in the “point-plane” electrode system at alternating current. The instantaneous voltage and the apparent charge have been measured depending on the root-mean-square voltage and the phase angle of partial discharges. This paper aimes at carrying out a statistical analysis of the obtained experimental results, in particular, the construction of a parametric probabilistic model of the dependence of the partial discharge inception voltage distribution on the value of the root-mean-square voltage. It differs from usual discharges which occur in liquid dielectric materials in case of sharp inhomogeneous electrode system. It has been suggested that discharges of a different type are the discharges in gas bubbles that occur when partial discharges in a liquid emerge. This assumption is confirmed by the fact that the number of such discharges increases with increasing the root-mean-square voltage value. It is the main novelty of this paper. This corresponds to the nature of the occurrence of such discharges. After rejecting the observations corresponding to discharges in gas bubbles, a parametric probabilistic model has been constructed. The model obtained makes it possible to determine the probability of partial discharge occurrence in a liquid at a given value of the instantaneous voltage depending on the root-mean-square voltage.

The aim of this paper is to present a new method of modeling of frost predicting process on the surface of the fine-and-tube air cooler. The advantage in comparison with existing similar models is a significant reduction in the number of operations performed to determine the optimal geometrical parameters of the heat exchange surface. In this paper presented structural scheme of mathematical model, described benefits and usage area. The study present the results of numerical modeling for ammonia air cooler with staggered tube bank and injection molding round fins. The model tested on range of values: coolant temperature (t0= –20, –27°C), temperature difference between coolant and ambient air (θ=7, 10°C), relative humidity (φ=90…98%), air velocity (w=3, 5, 7 m/s). Fin spacing permitted δ=10mm. The result of study shows the effect of the above parameters on the frost formation dynamic and frost distribution on tube rows along air flow. Presented program application allows providing improving of fin-and tube air cooler due to fin spacing optimization. Consequently heat exchange surface redistribute and increase on the area of maximum efficiency.

The paper is aimed to strengthen the controllability of electricity consumption mode at all structural layers of the country’s energy system (ES) to establish the optimal load curve in the PS. Following this goal, the energy system was broken down into seven structural layers - from the technological operation to the ES. For each layer, an expert assessment of the effectiveness of six institutional and operational methods of electricity demand-side management (DSM) was done. The integrated application of the suggested methods was tested in two industrial consumers, which proved the effectiveness of this approach for leveling their aggregated load curve. To ensure an appropriate economic impact on the electricity demand, given the influence of individual consumers on the load curve fluctuation in the ES, a particular price function considering the cross-correlation coefficient of the load curves was developed. It was proved that the complex DSM methods application significantly improved the controllability of the electricity consumption mode. To incentivize consumers to adjust their electricity consumption, a special price system functionally related to the cross-correlation coefficient of the consumer and the ES load curves was developed. The marginal price values depending on the cross-correlation coefficient were defined, while the intermediate price values were calculated by the functional transformation of the ES load curve into the price scale. The significance of the research results lies in the fact that ranking the DSM methods by the priority of application for various structural layers of ES and their integrated application almost doubled the DSM effectiveness.

The aim of the work is to create an interconnected numerical model of the magnetic, hydrody-namic and temperature fields of a ferrofluid sealer and to analyze thermal processes occurring in high-speed seals. This goal is achieved by selecting the necessary equations, boundary condi-tions, assumptions and physical properties of the magnetic fluid when building the numerical model of the sealer’s working gap, verification of the developed model by the results of the physical experiment. The important results of the work are the obtained and analyzed data on the influence both of physical properties and the geometry of the working gap of the ferrofluid sealer on the heating of the ferrofluid. With a shaft radius of 140 mm and a linear velocity at the shaft surface of 25 m/s due to viscous heating the ferrofluid temperature exceeding the ambient temperature can reach values up to 80 degrees and higher, it has been shown. The use of the equation proposed by V.E. Fertman to determine the thermal conductivity of ferrofluid and the mixing rule to determine its heat capacity allows us to describe with sufficient accuracy for en-gineering calculations the thermophysical properties of concentrated ferrofluids, it was shown. The significance of the results consists in the possibility of using the developed numerical model in the study of interrelated physical processes in the working gap of the ferrofluid sealer of ro-tating shafts. The physical and concentration parameters of the synthetic oil-based magnetic fluid given in the paper and the results of its test operation as part of a ferrofluid seal can be used to verify the results of newly developed models of ferrofluid devices.

Romania accumulated a useful experience in supporting high efficient cogeneration through a bonus type scheme. Spreading this experience to other countries that can choose a similar support scheme could lead to important savings and better results in developing this efficient tool. This state aid is operational, targeted to new investments stimulation for cogeneration technologies and replacement or existing plants rehabilitation. Present paper focuses on the results of support scheme after five years of its application: increase of number of producers who benefit of this aid, raising of general efficiency of high efficient cogeneration, important savings of primary energy and CO2 emissions avoided. On the other hand, use of this scheme showed a number of problems (to which this paper proposes adequate solutions) on institutional/administrative, investition, technical, economical-financial and social frameworks that influences beneficiaries and/or financiers of state aid.

This paper shows a techno-economical analysis on performance indicators of hybrid solar-wind-hydrogen power generation system which supply with electricity a low - energy building, located in Cluj-Napoca. The case study had the main objectives, as follows: cost estimation, evaluation of energy and environmental performance for a fuel cell integrated into a small-scale hybrid system power generation and estimation of electrolytic hydrogen production based on renewable energy resources available on the proposed site. The results presented in this paper illustrate a case study for location Cluj-Napoca. The wind and solar resource can play an important role in energy needs for periods with "peak load" or intermittent energy supply. However, hydrogen production is dependent directly proportional to the availability of renewable energy resources, but the hydrogen can be considered as a storage medium for these renewable resources. It can be said that this study is a small-scale model analysis, a starting point for a detailed analysis of Romania's potential electrolytic production of hydrogen from renewable resources and supply electricity using fuel cells integrated into hybrid energy systems.

As a public power distribution operator on low voltage (023/0.4 kV), medium voltage (6 and 20 kV), and high voltage (110 kV) in the territory of Galati County, SDEE Galati serves approximately 240,000 consumers (captive and eligible, domestic and non-domestic For this purpose, in the field of medium voltage underground distribution lines, SDEE Galati manages and operates a volume of approx. 500 km UDL/6kV circuit and approximately 630 km UDL/20 kV circuit. Many of these cables which are still in operation, were manufactured with materials and on the technological level of the ’60s,’70s and ‘80s decades and have reached the end of their service life. Evidence does and incident statistics from these networks in which, every year, one of the "tips" is the medium voltage cables damaged "technical wear" normal operating conditions. The current paper will present the main features of an innovating technological process called SPR (Sustained Pressure Rejuvenation), designed for on-site refurbishing of underground power cable insulation medium and high voltage. The process offers a viable alternative that has proven, over the 25 years of application initially on the American content and now on the worldwide, substantially more cost effective than replacing cables. The paper does not propose detailed presentation of the technological process, but to inform the family of energetics NPS about the existence and the benefits of applying this new technological process to the old cable medium and high voltage.

This paper presents the variant of phase shifting transformer that is made, unlike from traditional technology, on the basis of only one magnetic core. The paper describes the methodology related to the analysis of operation modes of device and its components. Additionally it presents a mathematical model of device with determines the relationship between input and output electric quantities as well as own longitudinal and transverse parameters of an equivalent circuit of phase shifting transformer (PST). Proposed configuration of PST is interesting from an economic and operational consideration; enable continuous control of power flow distribution in electric networks as a result of regulation a phase shift angle between input and output voltages of device.

The paper shows the importance of trending of partial discharge activity in assessing the insulation condition. It is presented the principle of the measurement method and the quantities that characterize partial discharges and also the criteria utilized for the assessement of the insulation condition of the hydrogenerators. Results of the measurements made on several hydrogenerators are presented, like the variation with time of the two main quantities that characterize the partial discharges, maximum magnitude, Qm and the normalized quantity, NQN over a period of about 10 years. Further, a classification of the insulation condition by 3 main and 2 intermediary categories and the definition of these categories are given. The criteria used for the assessment of the insulation condition are presented in the form of a table: quantitative criteria by the ± NQN and ± Qm values and qualitative criteria for the analysis of the 2D and 3D diagrams. At the end of each set of measurements, an analyze of the insulation condition annual evaluation is made, also a verdict is put, and of course, the recommendations made relating to the maintenance and the decisions that have been taken. The paper ends with several considerations on the method of on-line partial discharges and especially, on the conditions for valid trending activity in time.

This paper considers the problem of the influence of distancing elements in slot matrix channels on the thermohydraulic characteristics of the matrix of a rotary heat exchanger having various values of the height of the slot channels. The following tasks were carried out: mathematical modeling of thermohydraulic processes in different slot channels having constant height along them (from 0.3 mm to 0.5 mm); analysis of the influence of the slit channels' height, the number of distancing elements in rows, the distance between rows and the total number of elements on the average value of the Nusselt number and on the pressure drop; analysis of the effect of changes in speed and temperature conditions on thermal and hydraulic characteristics. The most important results are the following facts: the influence of the relative location of the distancing elements on the thermohydraulic characteristics of the flow is negligible; changes in the tempera-ture and speed regime of the laminar flow practically does not affect the intensity of convection in the matrix channels; an increase in the height of the slot channel leads to a relatively small decrease in the average value of the Nusselt number. The significance of the results obtained is that they can be the basis for adjusting the methods of design calculations of rotary heat exchangers taking into account the decrease in thermal effi-ciency caused by the presence of distancing elements in the channels of their matrices. Recom-mendations can be made to minimize the number of distancing elements without considering their mutual location.

Energy providing is a complex problem, which includes both common features for all categories of consumers and particularities, which emerge from the declaration on human rights. As an index of the level of heat using the concept of 'energy poverty'. In counterbalance, this concept proposes the use of the notion of "vulnerability" for these purposes. The concept of "vulnerable consumer" point of view of energy is still defined in the 2012 electricity law in Romania. In this context, the paper examines the vulnerability characteristics indicating meanings on widening energy paradigm by replacing the phrase "energy poverty" by "energy welfare". The paper presents quantitative issues regarding the current situation in Romania with explaining the need treatment paradigm change simplistic approach to the problem of vulnerable consumers, which really is a matter of national security.

The basic theoretical principles to create compact controlled transmission lines are analyzed in the paper. The results of technical and project elaboration of some variants of such type of power transmission lines are presented and the comparison between their technical and economic indicators with those of traditional power transmission lines and foreign analogues is made in the paper. The efficiency of compact controlled transmission lines application to form power systems and to create intersystem ties as well as distribution electric network is also stated in the paper.

The basic theoretical principles to create co mpact controlled transmission lines are analyzed in the paper. The results of technical and project el aboration of some variants of such type of power transmission lines are presented and the comparison between their technical and economic indicators with those of traditional power transmission lines a nd foreign analogues is made in the paper. The efficiency of compact controlled transmission lines application to form power systems and to create intersystem ties as well as distribution electric network is also stated in the paper.

The control system intelligence is determined by the ability to adapt to changing circuit-mode parameters. This approach is especially relevant for emergency automation, because the emer-gency depends on the huge number of factors. In addition, an accident can develop in cascade, causing uncontrolled and multiple changes in the grid topology and mode parameters. The for-mation of the control actions volume of emergency automatics is carried out on the basis of the computing of the mode on mathematical models of electrical grids, the accuracy of which de-termines the adequacy of the actions of automation, so the models verifying problem arises, in-cluding electromechanical parameters determining of the grid elements. The aim of the research is to develop methods for parameter identification of synchronous generators. The paper pre-sents two methods for identifying the synchronous generator constant inertia and the method for identifying the synchronous inductive resistance. The research of the proposed methods was carried out on the digital model assembled in MatLab Simulink, where the 200 MVA 13.8 kV generator was simulated. In addition, the research was performed using the physical electrody-namic model. The parameters of the generator 3000 VA 230 V were determined. The results of parameters determining by the classical methods of open-circuit and short-circuit are presented. The significance of these methods is that the generator is connected to the grid and is in an op-eration mode. This will make possible to form and refine the model online in accordance with the circuit-mode situation, which will increase the control actions adequacy.

Steganography is the perspective area of information security. The reliability of the stegano- graphic system, its stability is affected by the carrier – a container, which is considered in the paper as a digital image. The aim of the work is to increase the resistance of a steganographic system to attacks against an embedded message by developing a method for choosing a contain-er from a finite set of available digital images that ensures the transmitted message the minimum (close to the minimum) possible sensitivity of the generated steganographic message to disturb-ing influences under consideration with the selected steganographic algorithm. The goal was achieved using a theoretical study of perturbations of the formal parameters of the container ma-trix, as a result of steganographic transformation and active attacks, which made it possible to introduce a new formal representation for information protected from perturbing influence E, as the difference of low-rank approximations of container matrices and steganographic messages. The most important result of the work is the development of a container selection method ready for practical implementation. The efficiency of the developed method exceeds the efficiency of analogs, it remains high, regardless of the used steganographic method, which allows increasing the overall resistance of the steganographic system to attacks against the embedded message. The significance of the obtained result lies in the use of the developed method of increasing the stability of the steganographic system to attacks against the embedded message.

The work is devoted to the temperature control system at the outlet of a shell and coil heat exchanger with a variable heat exchange area, subjected to a change in the surface area by changing the level of the heated coolant in the heat exchanger. The aim of the study is to develop a model for the process of changing the heat exchange surface area and a temperature control system at the outlet of such a heat exchanger when the level of the liquid changes. The set goal is achieved by solving the following problems: development of discretization schemes for a system of differential equations describing the dynamics of the heat exchanger, development of an automatic control system for the temperature at the heat exchanger outlet by changing the heat exchange surface area of the heat exchanger and assessing the possibility of compensating disturbances. The most significant results are: discretization schemes for equations of dynamics of a heat exchanger with a variable heat exchange surface area, the use of which makes it possible to improve the accuracy of modeling and in the substantiation of the structure and choice of parameters of the controller. The paper presents two discretization schemes for differential equations of the dynamics of heat exchanger: a scheme using the method of lines and the method of running counting. It has been established that when using a scheme using two pumps to level control, the dynamics of the object depends on the sign of the derivative of the control signal.

The paper aimed to research mode characteristics of phase shift installation based on one three-phase transformer having three windings. Usually, such installations are two cores: exciting transformer and regulation transformer. In paper the installation functional scheme description, as well main relations which determine currents and voltages character in scheme elements during regulation process are given. It is shown, that installation is able to provide phase shift angle regulation up to . The installation scheme is designed to place the control module in the neutral connection point of regulation windings. Such solution allowing essential reduction of installation rated capacity compare to traditional one and excluding necessity of special isolation of shell. Proposed solution ensure in such mode compact construction and commodity for transportation, mounting and service.

In view of the high compatibility of the Walsh-Hadamard transform to the architecture of mod-ern computing facilities, it is sensible to use it in methods of steganography and steganalysis. Now, there are some efficient steganographic methods that use the Walsh-Hadamard transform domain for information embedding presented in the literature. It is known that to ensure the reli-ability of the steganographic message perception, information should be embedded in its high-frequency components; nevertheless, the issues of the correspondence of the Walsh-Hadamard transformants to the frequency components of the original matrix of the cover image are poorly researched. The purpose of this paper is to develop a formal sufficient condition for ensuring the reliability of perception of steganographic messages in the Walsh-Hadamard transform do-main. This purpose was achieved by establishing the relationship between the Walsh-Hadamard transformants and the discrete cosine transform transformants, which was theoretically substan-tiated in two ways, and experimentally confirmed. Based on the established relationship between the Walsh-Hadamard transform and the discrete cosine transform, as well as the components of the singular value decomposition of the corresponding matrices, a sufficient condition has been developed to ensure the reliability of the perception of steganographic messages in the Walsh-Hadamard transform domain. The sufficient condition consists in the fact that after embedding of additional information using any steganographic method, those Walsh-Hadamard trans-formants that correspond to the singular triples of the matrix corresponding to small (smallest) in value singular numbers, should change.

Nowadays, the energy systems are considered to be the main vital factor for the functioning of society. Today, this part of the infrastructure cannot exist without the informative infrastructure, so it needs efficient information and cyber protection. To detect the data integrity violations is one of the main tasks in the field of information security. In the paper, the digital images are considered as information content. The image integrity violation often results in the change of the original storage format. The format change is an indicator of the image transformation. At the same time, this fact can be considered as an indirect indicator of its integrity violation. The effective method for distinguishing the original image in lossless format from the image re-saved to lossless format from lossy format is developed in the current work. The proposed method is an improvement of the method developed by the authors earlier. The method is based on the analysis of the number of non-intersecting image blocks, in which the normalized gap of maxi-mum singular value increases due to the image's re-saving into a lossy format. The algorithmic implementation of the improved method allowed us to reduce the examination time in 38-56 times for more than 50% of images originally stored in lossy format compared to the prototype method. The algorithm efficiency was evaluated using Type I and Type II errors, as well as ap-plying the accuracy coefficient (ACC). As a result of testing, Type I error was not detected, Type II error rate was 3.6%, ACC = 0.98. The obtained estimations are independent of the quali-ty factor used when the image was initially saved in a lossy format. The developed algorithm is more efficient than almost all modern analogues, except for the prototype one. The theoretical basis of the proposed improved method makes it possible to use it for the study of the digital image integrity, violated by a minor disturbance, in particular for steganalysis in conditions of low capacity of the hidden communication channel.

The current paper provides a brief summary of the district heating system of the municipality Chisinau, including heat power sources, heat distribution network, production and consumption development over the past two decades and other data. Also, the priority investment projects realized by JSC "Termocom" are being presented. The company had implemented an automated monitoring system for the heat power production, transportation and distribution. For many years, the company used bellows pipes with polyurethane insulation, ball valves and plate heat exchangers. 14 out of 21 district heating boiler stations were upgraded 10 were completely automated having as a result no further need in full-time duty personnel there. The experience gained in the implementation of capacity banks and frequency inverters, summarizing the benefits and achieved results, is also presented in the current paper. It is to be underlined that in 2011 the company achieved decrease in electricity consumption by about 30% in comparison with 2005.

The paper deals with practical realization of efficient lighting system based on LED’s of 80W total power mounted on corridor ceiling total length of which is 120m and substitutes existing traditional lighting system consisting of 29 lighting blocks with 4 fluorescent lamps each of them and summary power 2088W. Realized lighting system is supplied from two photovoltaic panels of power 170W. Generated energy by PV cells is accumulated in two accumulators of 75Ah capacity and from battery by means of specialized convertor is applied to lighting system. Additionally, paper present data measured by digital weather station (solar radiation and UV index), which is mounted near of PV cells and comparative analyze of solar energy with real energy generated by PV cells is done. Measured parameters by digital weather station are stored by computer in on-line mode.

During operation of the transformer, the oil in it undergoes profound changes usually referred to as aging. The electrical insulating properties of it deteriorate, and sediments accumulate on the active part, which makes it difficult to remove heat. Inhomogeneous solid formations can induce not only the voltage breakdown, but also impair the parameters such as viscosity and other char-acteristics of the oil, which are important for the reliable operation of the power transformers. Aromatic groups initially is present in the transformer oil composition during the operation of the oil, and because of the aging processes, the concentration of the unsaturated cyclic com-pounds increases. The aim of this work is to develop a new method for the determination of the aromatic compounds and colloidal particles. This goal is achieved using a visual inspection of the transformer oil samples in the visible range. The most significant result of the paper is the establishment of a correlation between the acid number of the transformer oil (KOH), the tan-gent of the dielectric loss angle and the type of oil image under the visible light illumination. The significance of the obtained results lies in the fact that the presented method based on the analy-sis of the scattered and transmitted radiation, makes it possible to determine the presence of the aromatic compounds and colloidal particles in the transformer oil, as well as to define their con-centration and size. This method simplifies the analysis of the transformer oil quality, and re-duces the cost of the research, which is an important factor for the electric power industry.

An integral part of any open-type gas turbine plant is a low-emission combustion chamber, which is usually two-zone and cooled. One of the ways to reduce emission of harmful substanc-es is organizing low-emission low-temperature lean combustion with external heating of compo-nents. This paper investigates the effect of external heating of air and fuel gas on expansion of the lower combustion limit and stable flame position in a single-zone uncooled combustion chamber of a microgas turbine power plant. Stable position of the flame front in combustion chambers of this type mainly depends on the ratio between the average flow rate of the combus-tible-air mixture and the rate of turbulent combustion. This ratio depends on thermal, gas-dynamic, thermochemical and geometric factors. The purpose of this work is to substantiate the possibility of using the relative flow rate as a generalized characteristic. This goal was achieved in processing a large amount of published experimental data and numerical modeling of low-temperature combustion of lean mixtures. The most significant research result is determination of the range of relative flow rate (gk = 0.3…3.5·10-4 kg⁄s∙N), at which it is possible to ensure sta-ble flame position in a single-zone combustion chamber. Significance of the obtained results lies in the fact that using the relative flow rate makes it possible to quickly determine and analyze the geometric and gas-dynamic parameters and characteristics of turbulent combustion in com-bustion chambers of micro-gas turbine power plants.

The paper deals with a single-loop shield with an asymmetric magnetic coupling used for a magnetic field mitigation of a high-voltage three-phase cable line. The goal is to evaluate a thermal effect of this shield on a cable line capacity. To calculate the flat cable line capacity in the non-shielded case, we use a standard IEC 60287. To achieve the goal we carry out a numerical simulation of the thermal field when the shield is installed. Wherein, we deal with two specific sections. One is a long section with the shield being distant from the cable line. The other is a relatively short section where the shield is located near the power cables. The thermal field is applied for a long section in a two-dimensional formulation, and a three-dimensional formulation is used for the short section. Hence, we have obtained the dependences of the maximum temperature of the power cables on parameters of the shield and its location height above the cable line. The most significant allowable cross-sections of the shield cable and their location height have been determined, when the thermal effect of the shield does not decrease the cable line capacity. These results have ensured the maximum cable line capacity while shielding. The shield temperature is shown to exceed the allowable level in the short section. To reduce it the thermal backfill has been used. We recommend the values of its thermal resistivity to be used for different parameters of the single-loop shield.

This paper is devoted to the hot water production using photoelectric modules. The research goal was to estimate required photovoltaic array peak power to provide necessary hot water amount for an individual residential building in Uzbekistan climate conditions. To achieve this goal, the water heater operation has been simulated with TRNSYS software using data from NASA POWER meteorology database. To verify photovoltaic water heater mathematical models three-month experiment has been conducted. Operation with and without maximum power point tracking controller was considered. The main results are approximation equations, which were constructed basing on simulation outcome to estimate the required photovoltaic array power without numerical calculations for the region. As for electric boilers, consuming energy generated by traditional thermal power plants photovoltaic water heaters have been still considered inefficient and quite expensive. However solar collectors market growth slowdown and substantial decrease of photovoltaic panels cost make the heat generation by photovoltaic panels economically justified. Such photovoltaic panels application can be proposed as alternative to thermal and optical method of solar radiation concentration in solar heaters. The main advantage is a possibility to obtain any temperature from the generated electricity without limitations concerned with the coolant presence in the system The obtained results significance is concerned with highlighting of photovoltaic heating systems technical and economic competitiveness for some applications and with simplified calculation technique to estimate system composition for different climate conditions.

This paper discusses the problem of controlling electromechanical systems with maximum per-formance while maintaining accuracy and minimum power consumption. The objective of the study is to develop a law for regulating the coordinates of an electromechanical system, taking into account an energy-efficient algorithm for transferring the system from one operation point to another. An essential feature of the proposed solution is the possibility of applying the ap-proach in modern high-speed electromechanical systems operating mainly in transient modes, without providing additional requirements for the digital part. The objective is achieved through the use of the law of the rotor flux generation augmented with adaptive low-pass filtering of the flux reference at each sampling step. The proposed method is investigated in both steady-state and dynamic modes of operation using laboratory experiments with a 370-W induction machine. With appropriate control of the change rate of the magnetic flux, the losses during the full oper-ating cycle with changes in the torque can be significantly reduced compared to the conventional approach. The varying load is typical for the electromechanical systems with a variable moment of inertia and requirements for the positioning accuracy. The most critical result of the study is the reduction of the minimum possible cycle time, at which the expediency of using loss-minimizing control methods remains actual. The significance of the results obtained is in the re-duction of losses while maintaining the required torque, contributing to the more efficient opera-tion of this machine type.

The paper aimed at improving an economic mechanism for incentivizing distribution system operators to retrofit electricity networks and provide better services. The suggested approach envisages setting up operators' profitability relating to their rating scores, which were calculated considering essential criteria, in particular technical level of networks, efficiency, congestion, reliability, innovativeness, and quality of electricity. For this purpose, operators were ranked by the rating scores that allowed to elaborate methodology for distribution tariffs calculation individually. The essential findings: comprehensive assessment and ranking were based on an analysis of 20 key performance indicators of the networks' technical level; application of additive convolution considering the significance of indicators by Fishburn's weighting approach ensured their proper aggregation; using the principles of fuzzy logic, the aggregated values for the technical level of network infrastructure were calculated. The minimum tariff rates were computed for each operator according to the break-even point, with the maximum tariff rate being equal for the whole sample. A linear functional transformation provided a transition from the aggregated scores to specific tariff rates. Consequently, the best-rated operators received the maximum tariff rate, and the less-rated operators received relevantly lower rates. By varying the slope of the suggested tariff function, one can adjust the dynamics of the tariff rate change. The assessment of 24 operators allowed to verify the elaborated methodology for distribution tariff setting. The application of unbiased rating assessment by a set of designed sector-specific indicators allowed setting up adequate and efficient tariff rates aimed at incentivizing network upgrades.

The paper discusses options for district heating systems, including thermal power plants and heat pumps installed in individual heating centers of multi-story buildings. The aim of the work is to evaluate the energy efficiency of the options under consideration and the method of connecting piping to high-temperature return network water with a carbon dioxide heat pump. The goal is achieved due to the fact that one of the evaporators of the heat pump heating the new building or half of the existing building uses heat from return network water or from the first half of the building or from the whole building, and the second evaporator uses the heat of the outdoor air. Moreover, for high-temperature heating schedules, heat is taken out through a two-stage inter-mediate circuit containing two pumps, 2 heat exchangers and two expansion vessels. Significant results of the work are the developed scheme of the intermediate circuit of the carbon dioxide heat pump, which combines both the possibilities of working in a quantitative heat supply sys-tem and in the preparation of hot water for buildings during the non-heating period. The signifi-cance of the obtained results lies in the fact that the proposed technical solution allows to reduce fuel consumption for thermal power plants, consumers' expenses when paying for their con-sumed energy resources, increase the number of heat consumers connected to the thermal power plants through the use of heat pumps. The schemes of intermediate circuits of heat pumps for the quantitative law of regulating the operation mode of the heat supply system are also consid-ered.

The significance of this work is justified by the lack of experimental data on the operation of thermosiphons as part of the waste heat boilers (WHB) with gas turbine engines (GTE), whose capacity is from 2 to 10 MW. The aim of the work was achieved by physical modeling of the heat transfer process in the thermosiphon cavity in the range of heat loads from 0.5 to 17 kW/m2. The study of the internal temperature difference of two-phase gravity thermosiphons at thermal loads up to 17 kW/ m2 was performed experimentally. The paper shows a scheme of the experimental research stand. The graphical dependence of the temperature difference in the thermosiphon cavity on the heat flux density is presented. The root-mean-square error of experimental results was calculated, being up to 5.7%. The significance of the obtained results lies in that the existing calculation method was improved due to the mathematical dependences obtained for calculations of the internal temperature difference, and became applicable in the calculation of heat exchangers based on two-phase thermosiphons operating in the heat load range of up to 17 kW/m2. The experiments performed confirm the competitiveness and high thermal efficiency of the two-phase gravitational thermosiphons under the regime conditions typical for the WHB plants. This makes promising the use of the two-phase gravitational thermosiphons compared to traditional coil heating surfaces.

The paper examines a new approach of the finite volume method in determining the distribution of the electric field in non-homogeneous structures. The numerical calculation grid of the three-dimensional electric field is constructed using of the Delaunay triangulation concept and Voronoi cells. The purpose of the investigations is to simplify and order the algorithm for calculating the electric field distribution in non-homogeneous structures. The proposed algorithm is robust for calculating the potential and intensity of the electric field in non-homogeneous structures at the arbitrary distribution of voltage potential. The developed algorithm, during the computation process, ensures storage only the nonzero values of matrixes elements in the computer memory. The finite volume method keeps all the advantages of the finite difference method. Compared to the finite element method, the algorithm for constructing the finite difference relations is to simpler. In this case, there is no need to build a local and global rigidity matrix to form an equation solving system for the determination of capacitive coefficients of the electrical field. To solve the built system, we use the iterative method of conjugate gradients that converge very quickly for problems of the type examined. Numerical calculation of the electric field in the hollow cylinder with limited height and in the voltage divider from the glass-insulated micro conductors has been developed. The calculated the distribution of the electric field in the expanded voltage divider in the electrostatic screen. It is presented dates, which estimates the screen influence on capacitance of the voltage divider.

The aim of this paper is to increase the flight safety of an unmanned aerial vehicle that monitors power lines under the negative influence of electromagnetic fields on the on-board equipment. This problem was solved with algorithms for photo- and video-imaging and determination of wire sag. The development of monitoring algorithms should overcome the limitations of the ex-isting solutions. Particularly, various systems employ suboptimal routes of aerial vehicle, as well introduce non-universal constraints of flight zone. Besides, the considered approaches do not account for peculiarities of aerial imaging and for structural specifics of power line elements. This leads to poorer image processing performance and causes additional errors. To improve evaluation of power line characteristics, the algorithm of aerial imaging is proposed, which in-cludes vehicle position adjustment relative to wire for two imaging settings. To ensure safe per-formance of onboard hardware, a calculation methodology for electromagnetic field distribution is presented, which allows determine the minimum distance between the wire and the vehicle. Experimental results, obtained in simulator, show 90.22% accuracy of the proposed method. The most important research outcomes consist in achieved refinement of aerial imaging in over-head power line monitoring, as well in automation of wire sag calculation based on image data. The scientific relevance of the research consists in potential improvement of fault-tolerance of power transmission networks and decrease of power losses because of early recognition of power line failures and due repair. Consequently, maintenance costs of overhead power line service can be optimized.

The paper aims to provide argumentation of centralized district heating system use from the consideration of harmlessness for both public health and environment, in comparison with the use of individual heating units, installed in residential areas of the Chisinau municipality. Proposed goal have been reached performing the comparison on quantitative harmful emissions resulting from the operation of these two types of heating, using emissions factors, deducted from the specific consumption of thermal energy. The issue's relevance is proved by the existence of considerable number of disconnected users from the centralized heating, though last years, this trend is decreasing. As regard to new buildings, they continue to give priority to the individual heating. Statistical data provided by specialized institutions of the municipality underlines the increased share of incidents of intoxication with combustion products, namely carbon oxide, followed by poisoning from gas leaks, shingles caused by explosions in violation of the operating rules of such equipment, also registering lethal cases. New results are the determination of the difference in emission values for both cases. The importance of the obtained results is that for the generation of thermal energy in a centralized heating system using cogeneration technology, harmful emissions into the environment are 28% less than when using individual heat supply systems. This received ascertainment could serve as an important argumentation for the obvious priority of the centralized heating system in the municipality versus the use of individual units.

The aim of this paper was the development of a positional system model for a vector control of a static loads’ stand using the electrical drive and the study of the effect of various types of speed controllers and their settings on the dynamics of the transient processes during the simulation of the regulation and disturbance actions. This goal was achieved by the development of a vector control system model using the stand electric drive with the PID-speed controller setting, which ensured minimal speed errors and restrictions in the dynamic loads during the regulating and disturbing action. The synthesis of the current control circuits of the stator and speed in the torque control channel was performed. It was shown that using the existing PI-regulators of speed and current and their settings, the speed dynamic error was found to be as high as 21% at a regulating action, whereas during the disturbing action it was 8%. The achievement of the above indicators of the regulation quality was possible in the presence of the intensity setter at the speed regulator input. In this case the dynamic speed error while operating under control increased substantially. The introduction of the speed PID controller made it possible to reduce dynamic errors, however, it gave no desired results with the standard configuration. Changing the controller’s proportional part parameters allowed us to minimize the dynamic speed error while operation, both under regulating or disturbing influences.

The article presents the history of centralised distric0.t heating systems in Republic of Moldova, evolution, current state and prospects for short-term investments financed by raising funds from external creditors. Centralized heating in the Republic of Moldova is analyzed in the light of the activities of the license holders, regulated by the National Energy Regulatory Agency, particularly of those from mun. Chisinau and mun. Balti. In most cases, this centralized heating supply systems are in operation over 50 years already, so their rehabilitation is very appropriate considering their over dated lifetime period, and the moral and physical wear. At the level of heat sources, the physical wear of the fixed assets is about 70%. The heat transportation and distribution networks are being now renovated, using pre-insulated pipes from expanded polyurethane, at the level of 10%, and the growth of the renovated pipes share will lead to the lowering of the energy losses in this systems. The scope of the paper is the analysis of the key technical indicators and the description of the experience regarding the projects related to the enhancement of energy efficiency of centralized heating systems in mun. Chișinau and mun. Bălți, projects that are carried out in the last years, and implemented with the financial support of the foreign partners. Are analyzed main functioning indicators of the centralized heating systems for the period 2015-2018 years, inclusive production volumes, supply, and level of heat losses. A short analysis regarding centralized heating in some European Union countries, has been presented, as well.

This paper deals with the feedback speed control of a switched reluctance motor using the fractional-order controller. Due to the polar-pole construction and pulsed power windings, at which saturation of the magnetic system occurs, standard PI or PID controllers based on motor description with differential equations of integer order have led to significant errors and inaccuracies in the dynamic and static modes. The purpose of the work is optimization of dynamic and static modes using fractional integral proportional controllers. The goal was achieved by solving the problem of identifying a switched reluctance motor based on the fractional order differential equations with a power of 0.7, parameters found by genetic algorithms. It allowed taking into account the nonlinear dependences of the magnetic flux and torque so that the object behaved like a linear one. Then it became possible to synthesize controllers with a fractional order of integration and differentiation based on standard methods of the theory of the automatic control. It was shown that the parameters of the model changed with voltage regulation. The behavior of a closed system was compared when tuning the speed loop to the technical optimum and fractional order of astaticism , taking into account such changes in the control object. Significance of the results consisted in the fact that the fractional order controllers using a motor model based on a fractional-order differential equation ensured a high quality system (the minimum of the first matching time, the overshoot was no more than 2%), unattainable with classical PID controllers.