The main provisions are outlined of the author’s model of electric energy systems and their associations (Unified Energy Systems of Russia, UPS), enabling to determine analytically the key parameters of reliability of operation of EES within generation facilities (generation adequacy) and trunk power grids (transmission reliability) subject to dislocation of generation facilities and electric loads, electric modes and reliability of operation of trunk power grids.

For calculations of electric modes of operation of 750–220 kV power grids, Stott’s decomposition method is used involving simplification of the Jacobian matrix, the latter being divided into two independent subsystemsP → δ and Q → U, based on a weak functional link between P and Uand between Q and δ. When developing the model, much attention has been paid to improving the correctness in assessing the static and dynamic stability of the UES and taking into account these factors in the process of calculating the reliability of trunk power grids networks for each of the considered emergency situations. Special attention has been paid to improving the accuracy of estimates of economic losses (damage to the national economy) under various conditions of operation and recovery of UES: when working at low frequency, on actuation of automatic frequency load shedding (AFLS) devices and special load shedding automatics (SLSA), in case of sudden shutdowns, shutdowns with prior notice, and planned power supply restrictions. When forming the composition of consumers subject to restrictions, instead of the currently used proportional approach, the method of indefinite Laplace multipliers is used to reduce damage, based on taking into account the technological and economic response of various types of consumers to restrictions of their electrical loads. The calculations are concluded with an assessment of the annual average undersupply of electric energy and economic damage to consumers from disruptions of their power supply for the UES of Russia in 2017–2019, as a basis for optimizing the system reliability. It is shown that the probable annual average damage only in trunk grids of the UES of Russia amounts to as much as 1.2 percent of annual GDP, while its annual growth over the same period is estimated by the Ministry of Economic Development and the State Statistics Committee of the Russian Federation to be within 1.8%. Thus, due to the unreliability of the operation of only 750–220 kV main nets of UES, the national economy annually loses up to 2/3 of its annual growth.

One of the basic problems of electric power systems is the absence of normative documents regulating the operation, maintenance and repair of the capital equipment, the service life of which exceeds the normative value. We shall name them «old equipment» (OE). The essence of the difficulties to be overcome is reduced to the absence of methodologies for quantitative estimation of operational reliability and safety of OE, with the subsequent comparative analysis of OE. Considering the science intensity, cumbersomeness and labour intensity of solving this problem, the necessity of development of the relevant automated systems becomes indisputable. In this article, some features are considered of an estimation of an integral indicator and comparative analysis of unique facilities. Here, unique facilities mean those, which have no analogues in terms of the set combination of varieties of significant attributes. The methodological foundations of the synthesis of integral indicators are considered: ensuring the infallibility of the information base; requirements to evaluations of integral indicators; providing the physical essence of the integral indicator; possible types of integral indicators; the comparison of integral indicators of operational efficiency in the framework of the theory of testing statistical hypotheses for one-dimensional random variables is associated with a high risk of erroneous decisions; the assessment of the critical values of the integral indicator is carried out on the basis of simulation modeling within the framework of the fiducial approach.The development of automated systems for collecting and formalizing data on the technical condition of OE, the automated analysis and synthesis of these data, performing standardization of TEI, evaluating integral indicators and some results of comparative analysis, preparing operational recommendations to improve work efficiency, developing appropriate methodological guidelines, indicate the possibility of an objective assessment of the operational efficiency of OE and a decrease in the risk of unacceptable consequences. For an illustration of recommended methods and algorithms, technical and economic parameters of power units with SGI-400 are used.

The arrangement for heat supply of residential buildings with indirect connection to external heating systems is considered, providing reliability of heat input and required comfort in case of cold snaps after the official end of the heating season or before its beginning by supplying water from the return main of the heating system downstream the hot water supply heat exchangers. The calculations have been made to determine the amount of the main components of heat balance of a residential building on an example of one of standard projects being currently used in the climatic conditions of Moscow, subject to the structural characteristics of the building and its occupancy level. It is established that the actual heat output of the heating system when using the system of chilled water downstream the hot water supply heat exchangers as a heat source enables to main-tain an indoor temperature required for safe living conditions with the average daily outdoor air temperature above +2°C, the heat gain from solar radiation being moderate. It is proven that, tak-ing into account the thermal stability of the enclosing structures, the daily flow rate fluctuations do not significantly affect the stability of the temperature conditions of residential buildings or the comfort of their indoor microclimate at high outdoor air temperatures. It is noted that, in terms of reliability of heat supply of the main group of residential buildings and ensuring the life safety, the proposed arrangement is not inferior to the standard two-stage arrangement of connection of DHW heat exchangers with restriction of the total consumption of delivery water and with the associated regulation of heat supply for DHW, heating and ventilation. It is shown that the use of this arrangement involves virtually no extra costs, provides hydraulic resistance of the heating system and ensures a system-wide effect in the form of higher electricity generation at thermal consumption when using cogeneration.

The destruction of equipment metal by a brittle fracture mechanism is a probabilistic event at nuclear power plants (NPP). The calculation for resistance to brittle destruction is performed for NPP equipment exposed to neutron irradiation; for example, for a reactor plant such as a water-water energetic reactor (WWER), this is a reactor pressure vessel. The destruction of the reactor pressure vessel leads to a beyond design-basis accident, therefore, the determination of the probability of brittle destruction is an important task. The research method is probabilistic analysis of brittle destruction, which takes into account statistical data on residual defectiveness of equipment, experimental results of equipment fracture toughness and load for the main operating modes of NPP equipment. Residual defectiveness (a set of remaining defects in the equipment material that were not detected by non-destructive testing methods after manufacturing (operation), control and repair of the detected defects) is the most important characteristic of the equipment material that affects its strength and service life. A missed defect of a considerable size admitted into operation can reduce the bearing capacity and reduce the time of safe operation from the nominal design value down to zero; therefore, any forecast of the structure reliability without taking into account residual defectiveness will be incorrect. The application of the developed method is demonstrated on the example of an NPP reactor pressure vessel with a WWER-1000 reactor unit when using the maximum allowable operating loads, in the absence of load dispersion in different operating modes, and taking into account the actual values of the distributions of fracture toughness and residual defectiveness. The practical significance of the developed method lies in the possibility of obtaining values of the actual probability of destruction of NPP equipment in order to determine the reliability of equipment operation, as well as possible reliability margins for their subsequent optimization.

Deterioration and aging of the technical fleet of thermal power facilities lead to an unpredictable shutdowns of power equipment. Therefore, it is necessary to create a special approach in maintenance and repair programs, taking into account the possibility of predicting the moment of onset of the defect, its development, as well as the time of possible equipment failure. The equipment maintenance system used at the enterprises is based on the collection of retrospective data on defects and failures on the main and auxiliary equipment of the TPP and summarizing statistics on identical or similar equipment samples. Analysis of domestic and foreign methods of maintenance and organization of repair, as well as possibility of their application in modern power engineering is given. In order to create an efficient production asset management system, which addresses the problem of finding a balance between the potential risk of losses associated with both the operation of equipment and the cost of correcting defects, new class systems are now used in the software market, which carry out equipment maintenance based on the forecast. In order to optimize the equipment maintenance system and ensure uninterrupted and reliable operation of the equipment at minimum operating costs, as well as to reduce equipment downtime, unscheduled and emergency operations, it is advisable to use a modern approach to manage both reliability and risk, as well as the cost of asset ownership. This will enable to control the economic efficiency of the use of production assets. The necessity of creation of an algorithm of implementation of repair programs of power equipment base on technical condition for its use in digital power systems is shown. An algorithm is proposed for implementing the repair program of power units of electric power plants, including steam boilers and turbines of thermal power plants, differing by taking into account the technical condition of power equipment, which allows recognizing the defect that has appeared, determining the cause of its occurrence, its evolution and the duration of possible equipment failure. In the developed repair maintenance algorithm, it is proposed to make a transition from statistical empirical assessments of the technical condition of the equipment to objective estimates obtained on the basis of automated technical diagnostics systems and predictive analysis of situations.

The reason for the appearance of the first distributed generation in Russia was the high requirements to the reliability of power supply to power consumers of a special group of the first category of reliability. Diesel generating units were used to ensure uninterrupted operation. High costs for technological connection of consumers of the 1st and 2nd categories of reliability have strengthened the tendency to install a backup energy source in the enterprises' own power supply systems. However, setting reserves leads to a decrease in economic efficiency. There are additional costs for maintaining the reserve in a working condition. As a result, enterprises transfer the backup units to the mode of the main power source, and that of the backup function to the centralized power supply system. The creation of such industrial MiniGrid operating in a mode without power supply to the grid increases the cost of electricity for other consumers. Besides, with the departure of industrial enterprises from the centralized power supply, the share of communal and non-industrial consumers is growing. This requires an increase in the manoeuvrability of energy sources. The creation of balanced Energy Cells for energy supply to the population and small and medium-sized businesses that provide services to the population is not accompanied by the negative effects indicated above. In Russia, there are isolated examples of such systems, similarly operating in a mode without supplying power to the grid. Changes are needed to allow active consumers to supply excess capacity to the grid during peak hours in the UES of Russia, for which the grid companies need to be allowed to operate at least in a mode without supplying power to the grid, which will not lead to a decrease in grid companies' revenues from electricity transmission services. The introduction of these changes does not only lead not only to an increase in the reliability of power supply but also to an increase in the economic efficiency of the UES, which will reduce the price of electricity.

The problem of the influence of power fluctuations of wind farms due to the variability of the wind speed on the electric power system is considered. With high wind energy penetration, an increase in the operating reserve in electric power systems is required to cover possible sudden power fluctuations. One of the ways to reduce the stochastic nature of the wind farms power generation is their geographically distributed location. A method is proposed for the selection of capacity and distributed placement of wind farms, taking into account the factor of the variability of the total generated power. In each of the prospective areas for wind farm placement, the simulation of electricity generation by a single wind turbine with hour-by-hour breakdown is carried out using the developed WindMCA software based on long-term ground-based weather stations data. Optimization of wind farms capacity and their distributed placement in areas is carried out using a genetic algorithm in the MATLAB environment. The target function is the coefficient of variation of the power generated by all wind farms in the areas under consideration, depending on the number of wind turbines therein. Power duration curves are used in the final comparison of wind farms siting options. The application of the method is carried out on the example of the wind farms placement in the Zabaykalsky Krai. A solution has been obtained that provides a minimum coefficient of variation of the wind farms generated power and a relatively high capacity utilization factor. With a distributed location of wind farms, the duration of the period with the maximum output is reduced, however, the duration of low power generation is significantly increased. With an increase in the number of wind farms connected to various nodes of the electric power system, a certain guaranteed level of power generation can be obtained, which, ultimately, will reduce the required amount of the reserve of generating capacities.

The purpose of the article is to provide potential tools that can make a significant contribution to the identification of partial discharges (PD). Different types of partial discharges occur in stator winding insulation and a few partial discharges may occur simultaneously. Internal partial discharges are electrical discharges that occur in voids in the insulation of the stator winding. In typical stator insulation systems that use epoxy bonded mica tapes, insulation degradation due to internal partial discharges is usually slow (many years or decades). External partial discharges (slot PD and surface PD in the end-winding) are more dangerous and lead to the destruction of the insulation in a short time (several months or years). Therefore, the identification of insulation defects is essential. The analysis of existing methods for identification of defects in the insulation of high-voltage electrical machines using the results of measuring the partial discharges characteristics is carried out. The advantages and disadvantages of each of the groups of identification methods are characterized. It is shown that among the models of knowledge representation in solving problems of diagnostics of insulation systems for high-voltage electrical machines, identification methods, including field tests using training samples, are among the most suitable ones. It is noted that detection of insulation defects and their identification cannot be carried out only by direct measurements of PD characteristics and other dielectric parameters (electrical resistance, dielectric loss, polarization index). For this, special computing programs based on pattern recognition methods should be used. Results are presented of identification of technological defects in the insulation of the stator winding at the stage of factory testing, obtained using the PD identification method developed by the authors

The influence of phase current unbalance on the probability of occurrence of fire-hazardous situations in industrial premises that receive power in various power supply systems is considered. The theoretical prerequisites for the occurrence of fire-hazardous situations are described. It is shown that zero-sequence flows flowing through a neutral conductor in an unbalanced mode significantly heat it, which can lead to short circuits and conditions for the occurrence of fires. The results of studies of unbalanced conditions in Russia and abroad are presented. It is shown that the zero-sequence flows resulting from current unbalance lead to an increase in additional losses of active power and electrical energy. It is proved that additional heat losses caused by unbalanced power consumption can destroy the insulation of neutral and phase conductors, which is the main cause of short circuits and, as a result, fires. Based on the use of the Matlab graphical editor, dynamic characteristics of variations in phase and interphase currents and voltages, as well as the power loss coefficient, which characterizes the increase in heat losses, are constructed. The analysis of fires and their consequences for various objects in the Russian Federation is made. A computational unit has been developed in Matlab, which is used for calculating and plotting the dynamics of fires and their consequences over the investigated period of time. It is shown that the occurrence of fires and their consequences due to violations of the rules of operation of electrical installations occurs in any premises and sometimes reaches more than 20% of all possible causes of fires. Methods and technical means of minimizing zero-sequence currents as a means of preventing the occurrence of fire-hazardous situations are considered. The principle of operation of an automatically controlled shunt-symmetric device with a minimum resistance to zero-sequence currents is described.