Vortex and cyclone apparatuses are increasingly used for intensive flow of combined technological processes of pro-cessing (fine grinding, classification, drying, mixing, hydrophobization, etc.) dispersed materials. One of the types of equipment of this class with an active hydrodynamic regime is an apparatus with an upward (or downward) spiral-swirling gas-dispersed flow. The studies conducted by A.F. Frolov, V.I. Mushtaev, V.M., Ulyanov and B.S. Sazhin con-firm the high drying efficiency of highly moist dispersed materials. One of the tasks of a large-scale transition from laboratory facilities to industrial designs is the development of design features that determine the similarity of the hy-drodynamic regimes of heat and mass transfer processes. To determine the hydrodynamic characteristics of the gas-dispersed flow, methods based on the measurement of flow rates, velocities and hydraulic resistances were used. To establish the drying curves and the temperature curves of the polydisperse material (TPP hydraulic ash removal) of different fractions under various conditions of convective heat input, the kinetic method was applied. This method was based on measuring the moisture (mass) and temperature of the dried particles by selecting along their movement. The developed conditions and design measures allow for a large-scale transition from laboratory facilities to industrial de-signs without intermediate costly research on pilot plants. The generalized analytical and experimental data on the de-termination of the external heat and mass transfer characteristics of the drying process of dispersed material (hydraulic ash removal) in a vortex dryer depending on the hydrodynamic and structural parameters of the gas-dispersed flow have been presented. The presented experimental data allow suggesting the limiting effect of hydrodynamic phenomena that determine the efficiency of the drying process of dispersed materials in a gas stream.

The problem of structural-parametric synthesis of automatic control systems (ACS) of technological objects is deter-mined by the multi-dimensionality, multi-connectedness and nonlinearity of their mathematical models. Despite the indicated properties of such objects, traditional linear systems based on PID-algorithms are still used for process control. Since the synthesis of linear systems using input-output models does not take into account the multi-dimensionality and mutual influence of state coordinates, such systems increase the influence of parametric and signal perturbations on the quality of control processes. The increasing requirements for the quality and efficiency of technological processes control made it expedient to apply the control principle by the state vector based on the use of uninertial state regulators or combined state regulators including flexible feedback on the derivative state coordinates or state coordinate integrals. The research uses methods of system analysis of technological processes as control objects, methods of automatic control theory, methods of control systems synthesis on the state regulators basis, meth-ods of computer simulation. The linearized mathematical model of liquid-phase chemical reactor in the state space has been obtained. It has been established that the investigated object has the property of free movement stability and it is fully controlled in the state space. The problem of synthesis of a single-channel concentration vector control system in a chemical reactor using state regulator has been solved. The parameters of state regulator settings have been determined using the method of modal control. The efficiency of the automatic control system on the basis of the state regulator with an integral component has been shown using the method of computer simulation of the ‘nonlinear object – linear control subsystem’ complex. It has been demonstrated that the absence of an integral component in the control algorithm structure leads to a great static error of regulation. To eliminate the static error of control and ensure the robustness of the control system, it is recommended to introduce an integral component into the structure of state controller. This ensures the efficiency of the control system both for the case of complete measurement of the state vector and for the case of measurement of the output controlled variable only.

The complexity of transient processes during travelling-wave propagation in extra high voltage overhead lines is deter-mined by the fact that many frequency components are presented in the electromagnetic wave front. For the correct analysis of the aforementioned transient processes and for further development of travelling-wave-based relay protec-tion and fault location devices, it is necessary to take into account the parameters of the environment where electromagnetic wave propagation occurs. For the transmission line, these parameters are longitudinal inductance, longitudinal resistance, shunt capacitance and shunt resistive conductance. It is worth mentioning that for a variety of reasons unit-area longitudinal inductance and resistance are the parameters which depend on frequency, thus travelling wave velocity is different for different frequency components of the electromagnetic wave front. The popular researches which address this problem either fail to consider the dependence of overhead line inductance and resistance on frequency or this dependence is considered approximately for the high-frequency range, which can cause significant errors in the transient processes analysis during travelling wave propagation. In view of this, the development of the approach to overhead transmission lines simulation, which will allow both determining the line parameters in a wide frequency range and evaluating steady-state behaviour and transient processes in long-distance transmission lines, arrears relevant. The main research method to establish extra-high voltage transmission line parameters employs the simulation study in COMSOL Multiphysics. A number of assumptions were made in the simulation process: homogeneous soil layer, entire transmission line section and absence of transmission line conductor sag. The usage of finite elements method (FEM) for differential equation solution in the above-mentioned software is also seen as an assumption. The approach to extra-high voltage transmission lines simulation has been offered. This approach consists of the usage of Maxwell’s equations in combination with numerical integration with finite elements method (FEM). Frequency response for transmission line parameters and travelling-wave propagation velocity rate for different frequency components have been obtained. The results obtained can be used in updating of electrical power system models for further research in the relay protection field. The suggested approach will allow evaluating line parameters of other voltage types and obtaining more accurate values of transmission line parameters and travelling wave propagation speed along transmission lines for high-frequency range. The use of these transmission line models will enable to formulate approaches to improve the existing algorithms of travelling-wave-based relay protection and fault location devices.

Currently, when designing power transformers in order to take into account the influence of the asymmetry of the magnetic system on the operation of the device, especially in transition modes, engineering analysis packages based on field models are increasingly being used. However, such models are slow. At the same time, dynamic transformer models based on the magnetic circuit model are not inferior in accuracy to field models. Existing chain models of a three-phase transformer either do not take into account the asymmetry of the magnetic system or poorly integrate with simulation packages. The purpose of this article is to develop a dynamic model of a three-phase transformer which would allow considering the design features at the design stage, in particular, the asymmetry of the magnetic system and the influence of these features on arbitrary modes of the device operation. A contour current method was used to calculate a non-linear magnetic circuit of a three-rod transformer, and a single-step method based on a modified 2nd order Rosenbrock formula was used to calculate the electrical circuit. A nonlinear dynamic model of a three-phase three-core transformer based on the use of controlled current sources and EMF has been developed. This model is able to integrate with simulation packages including MatLab Simulink SimPowerSystem. The model allows taking into account the influence of the asymmetry of the magnetic system on the transformer operation in various operating modes including emergency and asymmetric ones. The novelty of the developed model can be seen in the approach to constructing a nonlinear matrix of magnetic resistances without explicitly using inductance matrices, which increases the accuracy and stability of the model considering the asymmetry of the magnetic system. The curves of transients in the characteristic operating modes of the transformer are given. The developed models can be used in the design of power transformers, including specific ones. They enable to increase the accuracy of the verification calculation and bring it to the level of simulation modelling. These models can also be applied for constructing digital twins of power transformers taking into account the influence of the design features of transformer equipment on the operation of power grids.

Development of energy-saving technologies offers good opportunities for selecting building energy supply methods through the use of alternative energy sources and power network types. Research in the field of energy saving is mainly focused on finding methods of energy saving by power consumers and individual power industry facilities. At the same time, collaboration of different energy networks as a unified power supply system of the city and a feasibility study of the energy load redistribution between different energy networks in the process of territorial development remains a poorly studied problem. The aim of the study is to develop a method that allows comparing the use of different power supply sources and types of individual buildings based on a single criterion of changing the total cost of transmission, conversion and consumption of energy in the city. The study employed methods of development and analysis of energy balances of a territory, methods for calculating gas, heat and electricity consumption of residential buildings, methods of power network losses calculation and methods of network and overlay analysis in GIS, materials of power providers’ and public utilities’ databases. A method has been proposed and implemented in the software package form for automating the calculation of the city’s housing sector energy balance for various placement options, power equipment deployment and connection of new or reconstructed buildings to the energy networks. The method is based on the use of an urban area energy balance spatial model in a GIS environment. The article presents an example of calculating the influence of different power supply options of one of the buildings in the city of Ivanovo on the energy balance of the city. The obtained results demonstrate the possibility of a comparative analysis of the options of connecting buildings to various energy network types based on a single criterion of minimizing municipal energy costs. The developed method and its implementation can be used to create decision-making information systems for regional and city governments.

Practical implementation of the process of thermal utilization of waste, including municipal waste, and processing efficiency largely depend on the plant design and operation modes. In their works, P. Basu, Safin R.G., Shantarin V.D. and others propose designs of plants for processing carbon-containing waste. The main disadvantage of such plants is the use of only one waste type (wood, biomass or plastic). Such plants operate at low humidity of the raw material, which lowers the quality of the produced gas. All this makes it an urgent task to develop a new plant design for disposing of waste of various compositions in a wide humidity range and to evaluate its performance efficiency. To evaluate the efficiency of the furnace for thermal waste utilization, we used the material and heat balance method that allows determining the plant efficiency and selecting the operation mode with the maximum efficiency value. This paper proposes a design of a two-chamber thermal reactor for waste utilization based on the combined method of drying and oxidative pyrolysis. The plant design allows you to organize the process of oxidative pyrolysis of raw materials in the reactor and to separate the flow of pyrolysis gas to the consumer from that for their own needs. The paper describes the algorithm of material and thermal calculation for drying and pyrolysis zones. It also presents an analysis of the thermal reactor with a capacity of 500 kg/h in different modes of oxidative pyrolysis depending on the moisture content of the feedstock. The developed plant design allows utilizing solid waste at its relative humidity from 4 to 50 % and reaching efficiency from 0,6 to 0,9 by changing the amount of oxygen fed inton the system from 1 to 10 %.

A promising method of monitoring rotor winding condition of induction electric motors ensuring higher reliability of their operation is spectral analysis of the external magnetic field signal. Modern methods of external magnetic field analysis use only the spectrum of this signal in the steady-state operation mode, which does not allow effective monitoring on a number of medium voltage electric motors of power plant auxiliaries operating with long start-ups (for example, machines with variable load, with a double squirrel cage, etc.). It is possible to evaluate the rotor winding condition of such machines in start-up modes, which means that an important task is to study the frequency-time spectra of the external magnetic field of the above-mentioned electric motors and to develop a method for monitoring the state of their rotor windings in the startup mode. In the study, the authors used two-dimensional models of two different types of motors representing drives of the mechanisms of draft systems at power stations. Both models are developed in the ANSYS software package. The calculation of the external magnetic field was carried out using the finite element method. The modelling was done for cases with or without defects. Signal processing was per-formed using the Fourier window transform method in the MatLab software package. Frequency-time spectra of the external magnetic field were built in the start-up mode on models of the investigated induction motors with the following defects: with dynamic eccentricity, with one broken bar of the rotor winding and without the indicated defects. The research results allowed us to develop a method for monitoring the rotor winding state of medium voltage electric motors of power plant auxiliaries operating with long start-ups. The method is based on detecting lower side frequencies of the fictitious rotor winding harmonics in the frequency-time spectrum during the startup. Their specific feature is «reflection» in the spectrum from the time axis. The developed method of monitoring rotor winding condition of the above-mentioned induction electric motors allows increasing the reliability of their operation by timely detection of faults in the rotor windings.

A common method of preventing scale formation on the internal surfaces of the condenser and heat ex-changers at thermal power plants with circulatory cooling systems (CCS) is correctional treatment with an addition of sulfuric acid for acidifying make-up water and reducing its alkalinity and the alkalinity of recycled water and dosing of oxyethylidenediphosphonic acid (OEDFK) for preventing scale deposit formation. The existing method of correction treatment does not provide the necessary degree of heat exchange equipment protection from scale formation. With this method of cleaning, it is impossible to completely remove deposits from the surface of the tubes to «pure» metal; the concentration of sulfates in the purge water often exceeds the permissible level. Improving the efficiency of water conditions requires developing a calculation method and creating a pilot plant for monitoring scale formation and corrosion through estimation of water chemistry directly in industrial conditions, which is the goal of this work. The circulating water corrosivity was studied on a stand that simulates the operation of circulatory cooling systems. The coil simulating water movement inside heat exchangers contained carbon steel and brass corrosion rate witness plates. A quantitative assessment of the biological contamination of the circulating water of the cooling system of the CCPP ПГУ-450 MW was carried out using total bacterial count (TBC) express tests. To estimate the probability of carbonate salt deposition in heat exchange equipment, we have proposed a method of calculating the existing values of the stabilization factor (calcium transport). The proposed method has been used to estimate the state of water chemistry of the circulatory cooling system of CHP PGU-450 MW. Calculations confirmed by the data of chemical analyzes of water and deposits have shown increased deposit mass values on the control samples (stabilization factor less than 85 %), including biological ones (the total bacterial count exceeded the permissible value by over 104 CFU / ml). The circulating water corrosivity also increased, and the corrosion rate of steel st. 20 exceeded the standard values (0,1 mm / year). The developed technique can be effectively used for analyzing the state of both the existing water conditions of circulatory cooling systems, and any other (alternative) water chemistry directly in industrial conditions of operation of a certain CCPP.

Shell-and-tube heat exchangers are widely used in different industries. Even a small increase in the efficien-cy of shell-and-tube heat exchangers can lead to significant energy savings. One of the ways to improve the efficiency of shell-and-tube heat exchangers is the use of pulsating flows for the enhancement of heat ex-change. Despite the fact that heat transfer in the tube bundle cross flow in steady-state conditions has been studied quite well, there is limited data on heat transfer in pulsating flow, which means that the problem of finding regularities of heat transfer with pulsating flows in tube bundles is still important. The work employs the incompressible Reynolds averaged Naviere-Stokes (URANS) equations and the continuity equation. Heat transfer is described by the convective heat transfer (Fourier-Kirchhoff) equation. The calculations are performed using Ansys Fluent. A numerical study has been conducted of the effects of forced asymmet-rical pulsating flow on heat exchange in in-line tube bundle cross-flow conditions. In the numerical experi-ment the Reynolds number Re ranged from 1000 to 2000, the relative pulsating amplitude A/D – from 1 to 2, the Strouhal number Sh – from 0,77 to 1,51, the Prandtl number and the duty cycle had fixed values: Pr = 7,2,  = 0,25. The relative transverse and longitudinal pitch was s1,2/D = 1,3. It has been found that pulsating flows lead to the enhancement of heat transfer in the whole range of the studied operating parameters. An increase in A/D and Sh leads to bigger Nusselt number Nu. An increase in the Re number leads to a de-crease in the Nu ratio in pulsating and steady flow conditions. The general correlation obtained based on the numerical study results can be used to predict heat transfer in a pulsating flow in the range of the studied geometric and operating parameters. More research is needed to predict heat transfer in a wider range of operating parameters and with other tube bundle configurations.

Simple and reliable zero sequence overcurrent protection in distribution 6–10 kV cable networks with an insulated neutral is most widely used for protection against single phase earth faults. However, protection of this type in many cases does not provide the required sensitivity to internal (inside the protected zone) faults as it must be tuned to the response current from surge transients during external faults through an intermittent arc. It is possible to increase the sensitivity if adaptive current protection is applied. However, the known methods for its implementation are only effective for stable faults through transient resistance but do not provide high dynamic stability of operation in transient conditions in case of arc intermittent earth faults that are the most dangerous for the network. Therefore, an urgent problem to be solved now is improving the principles of adaptive current protection against earth faults. To compare the efficiency of the known and proposed principles of adaptive current protection implementation taking into account the complexity of transients during earth faults through an intermittent arc in 6–10 kV cable networks, we used Matlab simulation with the SimPowerSystem and Simulink extension packages. The research into the operation algorithms of adaptive current protection against earth faults was carried out on simulation models of 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor. The studies on the simulation models have shown that the known methods of implementation of adaptive current protection against earth faults based on the use of full zero sequence currents and voltage are ineffective during intermittent arc earth faults. The authors propose a method of adaptive current protection against earth faults in 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor that provides a significant increase in dynamic stability of transient operation with arc ground faults and allows using only zero sequence current and voltage components of the operating frequency of 50 Hz as the actuating quantities. The proposed method of implementing adaptive current protection against earth faults in 6–10 kV cable networks with an insulated neutral and with neutral grounding through a high-value resistor does not only increase the sensitivity of this protection type to earth faults through transient resistence and dynamic stability of operation in transient condiitons in case of arc intermittent earth faults but also broadens the range of its possible applications