The normalized accuracy of the installed measuring instruments determines the scheduled measurement accuracy of the daily active load of an industrial enterprise. To maintain  it during operation, syntactic and semantic methods can be used to control the reliability of load measurements. During syntactic control, the state of measuring instruments that collect and process information about the enterprise’s load is diagnosed. Semantic control is based on the use of probabilistic characteristics of the measured load. The condition necessary for semantic control is the presence of information redundancy about the values of the monitored load. It is possible to control the load limit values (settings) when a priori information is known about the lower and upper limits in which reliably measured load values in normal operation of the enterprise may be contained. The article considers control methods that use a posteriori redundant information about the dynamics of load alterations in various sections of the daily schedule. These methods include monitoring by the first increments of the load, which characterize the speed of its alterations, as well as control using linear and nonlinear extrapolations of the first increments.  The results of the analysis of probabilistic characteristics of the daily active load of the enterprise and its first increments, which characterize the rate of load change, are presented. The effect of probabilistic characteristics of the first load increments on the boundaries of making a decision about the reliability of measurements is demonstrated. A comparative analysis of the effectiveness of reliability control methods based on the first load increments and their extrapolated values  has been carried out on the example of measurements of daily active load schedules of the “Minsk Motor Plant” JSC.

The methods of forming differential and restraining currents for busbar differential protection are reviewed; their advantages and disadvantages are considered. It is noted that differential protection according to instantaneous values has a shorter proper response time than for current ones, since it does not use digital filters. The response characteristic and principles of setting selection are studied. The effect of sampling on the operation of differential protection according to instantaneous values is analyzed. It was found that without the use of special measures, depending on the sampling step and the frequency of the signal, the response current would fluctuate within the mathematical error caused by sampling. A solution to this problem has been proposed. The method consists in applying piecewise quadratic interpolation and determining the values of inflection points of instantaneous differential and restraining current signals. The efficiency of the proposed method has been evaluated. It was found that its use reduces the error in determining the response current. For a sinusoidal signal, the maximum possible error was 0.02 %. The trajectories of operating point s of differential protection in case of external fault with saturation of current transformers have been analyzed. In this mode, protection for instantaneous values is more susceptible to false positives than for active ones. The method of exponential smoothing of the restraining current was considered and investigated. An exponential smoothing algorithm has been proposed and analyzed. It is concluded that exponential smoothing increases the stability of the differential protection according to instantaneous values to external faults. Exponential smoothing does not exclude the possibility of false positive of differential protection in case of external fault.

Incompliance of the settings of the system to control actual values of the parameters of a variable frequency induction electric drive may sometimes result in complete non-operability of a variable frequency electric drive as well as in the considerable reduction of the dynamic quality parameters. Such parameters as active rotor resistance, rotor inductance, and inductance of the magnetization circuit are available for the immediate measuring. They are not identified in terms of the acceptance tests, and the values presented in catalogues and reference books are calculated ones that may differ considerably from the real values of a certain machine. Despite constant studies by the researchers, a task to identify electromagnetic parameters of the equivalent circuit of an induction motor is still important and topical. The objective of the paper is to develop a method of online-identification of the electromagnetic parameters of an induction motor making it possible to implement accurate regulator adjustment of the frequency control system in terms of operational changes in the driving motor parameters. For the first time, the paper analyzes a steady mode of induction motor operation which does not apply T-network of the equivalent circuit of an induction motor. An approach has been proposed relying on the equation of an induction motor in three-phase fixed coordinate system obtained on the basis of the theory of generalized electromechanical converter.

 

Photovoltaic power plants have non-linear voltage-current characteristic, with specific maximum power point, which depends on operating conditions, viz. irradiation and temperature. In targeting the maximum power, it is by far known that the photovoltaic arrays have to operate at the maximum power point despite unpredicted weather changes. For this reason the controllers of all photovoltaic power electronic converters employ some method for maximum power point tracking. This paper makes an emphasis on model predictive controller as a control method for controlling the maximum power point tracking through the utilization of the well-known algorithm namely the Perturb and Observe technique. Further, during the advanced stages of this research study, the model will compare the results obtained for tracking the maximum power point from model predictive controller and a PID-controller as they are integrated Perturb and Observe algorithm. The obtained results will verify that the adaptive PID-controller Perturb and Observe algorithm has limitation for tracking the precise MPP during the transient insulation conditions. As compared to the proposed adaptive/modified model predictive controller for Perturb and Observe algorithm we illustrate that by adopting this method we will get to establish more accurate and efficient results of the obtained power in any dynamic environmental conditions: advantages as on regulation time (six times under the accepted experimental conditions) and by the number of fluctuations.

The Gas Institute of the National Academy of Sciences of Ukraine performs comprehensive studies of the formation of toxic emissions in the flame of atmospheric burners and beyond the visible burning cones (“rich” primary flame). The experiments are based on the proven significant content of harmful substances in the combustion products of gas fuel in household appliances and on direct contact of consumers with gas emissions during the operation of the stoves. A methodology for the experimental researches of the harmful emissions formation has been proposed while the computerized firing rig serving as the diagnostic facility has been developed for studying the combustion of hydrocarbon gases in the burners of household stoves. Carbon oxides CO and nitrogen oxides NO and NO₂ are considered as toxic emissions, while the primary air excess coefficient and the heat load of the burner are considered as variable parameters. Under operating conditions of a gas stove, its variable characteristics are the gas pressure in front of the nozzle of the atmospheric burner and its thermal power. When optimizing the design of burners, the determinant value of the stability of burning, energy and environmental indicators of fuel combustion is the coefficient of excess of primary air λ_pr at a given gas pressure before the burner. The influence of this coefficient on the formation of CO, NO, NO₂ is established, and the possibility of emissions with a high concentration of nitrogen dioxide is proved. Since the concentration of [NO] decreases with an increase in λ_pr, and the absolute level of [NO₂] concentrations is not significantly affected by the value of λ_pr, it is determined that the proportion of [NO₂] concentration in the [NO_x] = [NO] + [NO₂] compound increases with an increase in the primary air excess coefficient.

The article presents rationales for choosing the depth of installation of an oil jet pump in the borehole that which ensures maximum efficiency of its operation. The operating parameters of the ejection system are determined by the joint solution of the characteristic equations of the high-pressure jet pump and the hydraulic system. In the process of solving the system of equations, the method of successive approximations, the Delphi software environment and PTC Mathcad resources were used. The equation of the characteristics of the jet pump hydraulic system was obtained by determining the pressures in its distinctive cross-sections and then presenting their values as the relative (dimensionless) head of the ejection system. Alteration the installation depth of the jet pump changes the characteristics of its hydraulic system, the parameters of the operating point of the pumping unit and its efficiency. In this case, the minimum permissible installation depth of the jet pump is determined by the value of the minimum pressure in the elements of the ejection system, which must exceed the value of the elastic pressure of saturated vapors of the oil and gas flow and ensure its operation in pre-cavitation mode. The probability of operation of a jet pump in cavitation mode was studied using the Bernoulli, Darcy – Weisbach and flow continity equations. The inversely dependence of the ejection coefficient and efficiency of the jet pump on the depth of its installation in the borehole has been revealed. If the jet pump is installed in the borehole at the optimal depth, its efficiency is increased by 30 %.

Thermosyphons and heat pipes offer great opportunities for creating pas sive heat and mass transfer systems. Various design solutions using heat pipes (thermosyphons) in solar energy systems are known. Solar energy is one of the promising energy sources, a step towards reducing dependence on other energy resources. To date, there is already an industrial production of solar collectors based on thermosyphons (heat pipes). In solar collectors, the use of thermosyphons (heat pipes) makes it possible to simplify the assembly of the structure, ensures its high modularity, maintainability and reliability. In the course of research, the authors have developed and justified the design of a solar collector based on thermosyphons fixed on panels that absorb solar rays. In order to analyze the efficiency of the solar collector based on two-phase copper thermosyphons, two models of solar collectors were created, viz. the one with a flat absorbing panel and the one with a cylindrical absorbing panel. The areas of the absorbing surfaces were the same. Both models were studied by the method of thermophysycal experiment. The results of studies of the effectiveness of the above-mentioned solar collectors have been obtained. The efficiency of the solar collector based on a copper two-phase thermosyphon, which is fixed on a cylindrical absorbing panel is 2–5 % more than the efficiency of the solar collector based on a copper two-phase thermosyphon, which is fixed on a flat absorbing panel. The maximum efficiency value obtained at low initial water temperatures for solar collectors with a cylindrical and flat absorbing surface was 60 %.