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RELEVANCE. Thermal imaging control is used to monitor the technical condition of electrical equipment, as well as contacts and contact connections of switching devices, which allows to increase the efficiency of work.OBJECT. Timely detection of defects of contacts and contact connections of low-voltage switching devices to prevent emergencies.METHODS. Determination and control of technical condition of electrical equipment, contacts and contact connections of apparatuses in real time by means of indicators and thermal imaging control.RESULTS. The values of contact heating temperatures from material and type of contact connections were analysed. The criteria for estimation of the state of contacts of switching devices with the help of indicators of their state have been determined. The optimum values of loading coefficients of the circuit breaker in moulded case VA04 and contactors KMI and KTI are obtained. Emergency cases at the industrial object are shown, which prove the necessity of application of indicators and thermal imaging control as one of the tools of automation of technical condition control of low-voltage electrical equipment.CONCLUSIONS. The offered noncontact method of estimation and control of technical condition of electrical equipment, contacts and contact connections of devices in real time with the help of indicators and thermal imaging control allows both to receive data in real time mode and to increase inter-repair periods for power equipment and to increase reliability of operation of the whole system.

Purpose. There is a trend of transition from a purely centralized power supply to a combined one, the number of local decentralized sources of electricity directly in the distribution networks is increasing. Distribution electric networks are transformed into a network with features characteristic of a local electric system, which receives power both from its own distribution electric networks and from a centralized source. Renewable energy has a number of advantages, but there are also disadvantages. Among them - the complication of the operation of electric networks with the growth of the capacities of renewable sources of electricity installed in them and the instability of generation due to their natural dependence on meteorological conditions, if we talk about technical shortcomings, then this refers to the sinusoidal nature of voltages and currents and voltage deviations, ensuring the quality of electricity which directly depends on ensuring the balance of active and reactive power in the electrical system. The purpose of this article is to analyze the effectiveness of reactive power compensation devices as a tool for reducing the threshold of integration of distributed generation sources into the electrical networks of Ukraine. The task is to study the reduction of the integration threshold for distributed generation. Research methods. Mathematical modeling of an electrical system with distributed generation elements and reactive power compensation devices. The influence of the operation of reactive power compensation devices on the parameters of the electric network is studied. Comparative analysis of network parameters and their change when implementing distributed generation together with and without reactive power compensation devices. The results obtained. The obtained results show that the use of reactive power compensation devices makes it possible to increase the carrying capacity of operating power lines and transformers, which is especially important when most of the power system schemes where distributed generation is integrated are of radial type, i.e. it actually lowers the integration threshold for renewable generation in the electric network. A very important factor is that the introduction of reactive power compensation devices together with distributed generation solves the problem of stabilization and voltage loss in electric networks, and also improves the quality of electric energy. Scientific novelty. The method of selecting reactive power compensators for distribution networks has been further developed, which differs from the existing ones by taking into account the presence of renewable energy sources of various types, which allows to increase the efficiency of the interaction of the local electric network with the renewable generation integrated in it. Practical value. It consists in lowering the integration threshold of distributed generation sources into electric networks by introducing reactive power compensation devices together with them, which affects a number of technological parameters in the node - reduction of power and voltage losses, stabilization and control of voltage, improvement of electric power quality indicators.

The concept of forming an objective function for solving the problem of the quality of electrical energy optimizing in power networks is proposed, which takes into account the uncertainty factor of information about the mode parameters. This will allow, in contrast to the traditional binary function of assessing the quality of electrical energy for compliance with the established standards, to take into account the dynamics of changes in the efficiency criterion and perform the search for optimal values of the relevant controlling influences. The classification of information flows about the mode of the electric network is presented and the boundaries of fuzzy set for the values of the mode parameters are defined. It is shown that the objective function should be appropriately formed on the basis of fuzzy logic. The principles of the formation of fuzzy mathematical models for the analysis of established normal modes of the electrical network are defined. It is proposed to determine the membership function of a fuzzy set taking into account the quality of information that can be provided by the technical means of the electrical network. Ref. 5, fig. 3.

The operational cost of a microgrid is significantly influenced by the response of storage systems and the complexities of the power market’s tariff structures. This paper addresses the challenges arising from the coexistence of new market entries and traditional tariffs, which contribute to a complex market environment. To tackle this issue, the paper establishes a microgrid market environment encompassing four types of tariffs. By modeling the response of electric storage and cold storage in a microgrid, the study formulates a non-linear mixed-integer optimization problem. Numerical studies are then conducted to verify the model and analyze market performance. The results reveal a trade-off in behavior among different market entries when optimizing the total cost of microgrid operation. These findings shed light on the complexities and trade-offs involved in microgrid operational cost optimization within a diverse market environment, offering valuable insights for market participants.

Abstract Realizing a lithium sulfide (Li2S) cathode with both high energy density and a long lifespan requires an innovative cathode design that maximizes electrochemical performance and resists electrode deterioration. Herein, a high‐loading Li2S‐based cathode with micrometric Li2S particles composed of two‐dimensional graphene (Gr) and one‐dimensional carbon nanotubes (CNTs) in a compact geometry is developed, and the role of CNTs in stable cycling of high‐capacity Li–S batteries is emphasized. In a dimensionally combined carbon matrix, CNTs embedded within the Gr sheets create robust and sustainable electron diffusion pathways while suppressing the passivation of the active carbon surface. As a unique point, during the first charging process, the proposed cathode is fully activated through the direct conversion of Li2S into S8 without inducing lithium polysulfide formation. The direct conversion of Li2S into S8 in the composite cathode is ubiquitously investigated using the combined study of in situ Raman spectroscopy, in situ optical microscopy, and cryogenic transmission electron microscopy. The composite cathode demonstrates unprecedented electrochemical properties even with a high Li2S loading of 10 mg cm–2; in particular, the practical and safe Li–S full cell coupled with a graphite anode shows ultra‐long‐term cycling stability over 800 cycles.

Calculations of steady-state modes of a complex electric power system are significantly simplified if we use the coefficients of distribution of the setting currents. The use of the theory of directed graphs for the formation of the matrix of the coefficients of distribution of the setting currents is directly related to the determination of the values of all possible and specific trees of the graph of a complex electric network. The authors have developed and implemented an improved algorithm. calculation of current distribution coefficients of the electric power system. The concepts of the “base” of the graph and the “hanging” contour are introduced. In this case, to calculate the current distribution coefficients, it is necessary to take into account all possible and specific trees of only the graph base. A method is indicated for supplementing the matrix of current distribution coefficients of the graph base to the current distribution matrix of the original graph. The paper proposes methods for simplifying the network topology based on the development of diacoptic principles.

The article presents an analysis of electromagnetic transient processes in long ultra-high voltage transmission lines, taking into account shield wires. It was shown that EMTP and Matlab/Simulink software are currently widely used in the study of transient processes in power lines. The EMTP software package uses the finite element method when integrating the equation that mathematically models the distributed parameter transmission line. The Matlab/Simulink software uses the d’Alembert method. In both cases, it is not known how the boundary conditions for the partial differential equation that mathematically models the transmission line are determined. The power line is analyzed as a distributed parameter system, described by a second-order partial differential equation. The advantage of the proposed method of calculating the boundary conditions for the abovementioned equation is the use of boundary conditions of the second and third types of Neumann and Poincaré, which allowed us to take into account the mutual influence of shield wires and phase conductors of the line in one power system. On this basis, the methodology for obtaining time domain graphs, spatial distributions, and traveling wave distributions of voltages and currents for phase conductors and line shielding wires is presented. The results of a computer simulation of transient processes when switching on the power line, taking into account controlled phase commutation and under single-phase earth fault conditions, are presented. All calculation results of transient processes presented in the article were obtained exclusively using numerical methods.

The article considers the possibility of determining the source of higher harmonics of currents and voltages in the electrical network in the directions of power of the respective components. The research purpose is evaluating the effectiveness of theoretical methods, computer modeling of a fragment of the electrical network and electrical load receivers operating in parallel. Different combinations of active, reactive and nonlinear loading are investigated. Larionov's scheme was used as a nonlinear load. According to the results of the study, conclusions were made about the effectiveness of the method used. Thus, in particular, in the case of parallel operation of nonlinear and mixed active-nonlinear load, the source of higher harmonics is determined incorrectly. Suggestions for ways to improve the algorithm are made.

Photovoltaic (PV) systems have been rapidly implemented in commercial facilities without determining the negative impacts that may result when connected to the facilities' electrical power system. The research presented shows the results of a study of the quality of electrical energy in a commercial installation in which there were no problems before implementing the PV system. Measurements of different parameters of the energy generated by the photovoltaic system and that provided by the electrical network are carried out, carrying out a simulation using the Helioscope software. As a result of the work, voltage variation and current harmonics problems are identified, carrying out a technical and economic analysis of implementing a passive filter that performs the respective corrective actions.

The paper presents aspects regarding the construction and operation of hybrid plants consisting of renewable energy sources, electrolyzes and hydrogen and electricity storage facilities that have been obtained. The authors analyze the energy processes in hydrogen production stations in order to optimize operating costs. The cheap electricity obtained for example through photovoltaic panels, can supply the electrolysis stations and the resulting hydrogen in this case, will have low production costs without negative ecological impact. At the end of paper are stated some conclusions that resulted from the study.

The study results of overvoltages during arc single-phase earth faults of intermittent nature in the 35 kV electric net-work with isolated neutral are presented. With the help of computer simulations of transients in the electrical network, the maximum multiplicities of overvoltages at the point of occurrence of single-phase arc earth faults have been ob-tained. According to known theories of the occurrence and development of overvoltages, it exceeds theoretically ex-pected. The change of the overvoltage level on the 35 kV busbars of the network substations, electrically connected to the place of occurrence of the single-phase earth fault, has been shown. The influence of the cable line on the overvolt-age multiplicity is shown. Ref. 12, fig. 3, table.

This paper deals with the reduction in electrical losses and the minimization of voltage deviation in electrical power grids. To this end, a novel heuristic-based approach is proposed for controlling reactive power injections along an electrical grid with distributed generation using distributed photovoltaic (PV) generation. The proposed approach consists of applying a heuristic, namely a genetic or firefly algorithm, to solve the loss and voltage deviation optimization problem by controlling PV reactive power injections. The proposed method was tested on a radial 100-bus network with an intense penetration of PV generation. The obtained results indicate that the proposed method consistently yields superior grid performance when compared to algorithms previously proposed in the literature. In fact, it led to a reduction in the active power supplied by the reference bus to the grid, thereby alleviating the burden imposed on the most upstream parts of the distribution network. As a consequence, the proposed method contributes to a power-efficient network, enhancing its loss performance and voltage stability.

Smart Grid technology will revolutionize modern industries providing powerful solutions to increase the efficiency of traditional Electric Grids. Smart Grid is an energy supply network that uses digital communications technology. The increasing load and consumption demands increase electricity complications, for instance, the demand has increased, along with problems like blackouts, overloads, and voltage sags as well as current electrical network growing critical carbon emissions and foremost dealing with cyber-attacks. However, the Smart Grid technology originates with vulnerabilities and complications especially for securing information which is the most vital concern. This article analyzes the threats and potential solutions of smart grids based on the Internet of Things. We focus on the types of cyber attacks and provide in-depth information The cyber security status of the smart grid.

One possible device authentication method is based on device fingerprints, such as software- or hardware-based unique characteristics. In this paper, we propose a fingerprinting technique based on passive externally measured information, i.e., current consumption from the electrical network. The key insight is that small hardware discrepancies naturally exist even between same-electrical-circuit devices, making it feasible to identify slight variations in the consumed current under steady-state conditions. An experimental database of current consumption signals of two similar groups containing 20 same-model computer displays was collected. The resulting signals were classified using various state-of-the-art time-series classification (TSC) methods. We successfully identified 40 similar (same-model) electrical devices with about 94% precision, while most errors were concentrated in confusion between a small number of devices. A simplified empirical wavelet transform (EWT) paired with a linear discriminant analysis (LDA) classifier was shown to be the recommended classification method.

Introduction. A significant proportion of earth faults in 6 - 35 kV networks is a transient and short-lived process, which is followed by an electric arc. Problem. In such cases, earth-fault protection that responds to steady-state current and voltage is not able to operate properly. Also, the use of the Petersen coil to compensate for the capacitive earth fault current complicates the protection function because it significantly reduces the single phase earth fault current in steady state. Purpose. To develop selective single-phase earth faults protection algorithm using harmonic components that occur in zero-sequence currents and voltage in the transient process. Method. A mathematical model of the power supply system is applied to study the frequency components of currents and voltage of zero sequence in compensated electrical networks with phase-to-earth faults, and a mathematical model is used to test the operation of the developed protection algorithm. The results showed that, the reactive power for harmonic components of the frequency greater than 100 Hz, which are separated from the current and voltage of zero sequence in compensated electrical networks on the damaged feeder, is positive regardless of the degree of compensation of the capacitive current. That may be the basis of the principle of directional protection. Originality. Phase-to-earth fault selective protection algorithm has been developed. In that algorithm, first derivatives of currents and voltages of zero sequence are found, to reduce the influence of aperiodic components. And then, by using of the Fourier transform, a number of harmonic orthogonal components are extracted from them. Reactive power is calculated for each of frequency component and their total sum is found. If that sum excess of threshold, the relay will make a decision. The reliability of the developed protection algorithm is confirmed by the results of mathematical modeling and verification of the test sample at the laboratory stand and by means of field signals that were recorded by digital loggers at the substations.

A novel relation between the Moore-Penrose inverses of two nullity-1 n × n Hermitian matrices which share a common null eigenvector is established, and its application in electrical networks is illustrated by applying the result to Laplacian matrices of graphs.

Assessment of electrical network vulnerability based on complex network theory (CNT) has attracted increasing attention. However, CNT focuses on analyzing the structural vulnerability and has significant limitations regarding operational vulnerability. To address the lack of a comprehensive CNT-based framework to assess operational vulnerability, a temporal-spatial correlation graph (TSCG) that considers the topological, physical, and operational characteristics of electrical networks is proposed. To better assess vulnerability, two metrics, i.e., impact ability and susceptibility of branches, based on symmetric entropy from the load redistribution mechanism of electrical networks and their corresponding TSCGs are proposed. Applications to IEEE 39-bus system, IEEE 118-bus system, and French grid demonstrate that the proposed TSCGs have distinctive features that can intuitively and simply reveal the features of impact ability and susceptibility in CNT.

The paper structured in five parts, aims to highlight the importance of an integrated management as to ensure a high efficiency and a smaller time to recovery of the investment for a small hydropower plant (SHP). In the context of sustainable development of the energy sector, due to the shortage of budgetary funds, a large amount of interests of all participants in the process must be correlated: the interests of investors - which provides funding and execution; general economic and social interests of local communities, the regulated legislature protected by state institutions. First is analyzed the importance of the study of the infrastructure energetic efficiency, in the current economic context, followed by a presentation of the optimum solutions of planning of such SHP. In third chapter are analyzed some factors that influence the optimum functioning of the SHP and in the fourth part the benefits of a real energetic management. In final chapter is presented the numerical model of the combined management and some obtained results. The paper ends with some conclusions and references.

This paper presents a stability analysis of a buck converter using a Zero Average Dynamics (ZAD) controller and Fixed-Point Induction Control (FPIC) when the control parameter N, the reference voltage υref, and the source voltage E are changed. The study was based on a previous analysis in which the control parameter was adjusted to N=1 and the parameter K_s was changed during the simulation, finding the stability zone and regions with chaotic behavior. Thus, this new study presents the transient and steady-state behaviors and robustness of the buck converter when the control parameter N changes. Moreover, numerical simulation results are compared with experimental observations. The results show that the system regulates the output voltage with low error when the voltage is changed in the source E. Besides, the voltage overshoot increases, and the settling time decreases when the control parameter N is augmented and the control parameter K_s is constant. Furthermore, the buck converter controlled by ZAD and FPIC techniques is effective in regulating the output voltage of the circuit even when there are two delay periods and voltage input disturbances.

The article considers the influence of opportunities forcing synchronous generator (SG) and a synchronous motor (SM) to provide the required level of the residual voltage at the consumer at short circuits in networks of high voltage. It determines the ability of the equipment to remain in the work during such perturbation by mathematical modeling.

Internet-connected devices will represent an increasing proportion of the load served by electric power systems. As these devices could conceivably be hijacked and controlled remotely by a malicious actor, they could represent a new threat vector against the dynamic security of a power system. Such attack strategies have not been considered in the existing literature on power system cybersecurity. As an initial scoping exercise, the present case study explores whether such devices could be remotely hijacked and then maliciously power-cycled at particular frequencies to deliberately provoke harmful oscillations in an electrical grid. To gauge the broad feasibility of this novel style of attack, dynamic simulations are performed on two representative test power systems, at differing levels of attacker and defender resources. These simulations show that power-cycling just 1% of consumer loads at a system's resonant frequency may sometimes provoke harmful electromechanical oscillations throughout a national grid. This novel simulation exercise, therefore, implies that cybersecurity vulnerabilities at the consumer side could jeopardise the physical integrity of a nation's entire electricity supply.

With the fast development of wind power generation, large-scale wind farms are connected to an electrical network which is series compensated to increase transmission capacity. However, a series-compensated power system may encounter with a sub-synchronous resonance (SSR) problem. Flexible AC transmission systems controllers are widely applied to mitigate SSR and improve the transient stability of the power system. A static synchronous compensator (STATCOM) with an SSR damping controller is proposed to mitigate the potential of SSR in a series-compensated doubly fed induction generator-based wind farm. The local signal is used as the input of the damping controller, which is feasible to be implemented in a practical project. Taking account of different series compensation levels and operating conditions, extensive transient simulations have been carried out using power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) to demonstrate the capability of STATCOM in damping SSR. It is shown that the SSR is successfully alleviated by STATCOM, which also verifies the effectiveness of the proposed STATCOM controller in improving the stability of the transmission system.

For electrical networks with voltage of 6-35 kV with a compensated, isolated or resistor-grounded neutral, a phase-to-ground protection has been developed, in which, based on the results of the time-frequency wavelet transform of zero-sequence currents, voltages and their derivatives, using the obtained analytical expression, the total reactive power wavelet for different frequencies is determined. It is shown that at the initial moment of a phase-to-ground fault on the damaged feeder the power is always positive, and on the undamaged feeder it is negative, regardless of the operating mode of the neutral. Wavelet transform coefficients are found by convolution of discrete values of measured signals with sine-cosine signals of the Morlet mother function. The time-reversed sequence of these signals is obtained using a matrix for which the rules for its formation are stated. An excess of the zero phase sequence voltage amplitude of the set value is used as a starting protection element. With the help of a mathematical model of the network, studies of the behavior of protection in case of blind and arc phase-to-ground faults at various degrees of compensation of capacitive currents, at various voltage values at the moment of the short circuit have been carried out. In all modes, a reliable protection operation is obtained, the sensitivity of which is an order of magnitude higher than the protection based on Fourier transforms. Positive results of testing a protection sample implemented on a microprocessor-based element base at a laboratory stand are obtained. References 20, figures 7, tables 2.

This work presents a new coordinated operation (CO) framework for electricity and natural gas networks, considering network congestions and demand response. Credit rank (CR) indicator of coupling units is introduced, and gas consumption constraints information of natural gas fired units (NGFUs) is given. Natural gas network operator (GNO) will deliver this information to an electricity network operator (ENO). A major advantage of this operation framework is that no frequent information interaction between GNO and ENO is needed. The entire framework contains two participants and three optimization problems, namely, GNO optimization sub-problem-A, GNO optimization sub-problem-B, and ENO optimization sub-problem. Decision sequence changed from traditional ENO-GNO-ENO to GNO-ENO-GNO in this novel framework. Second-order cone (SOC) relaxation is applied to ENO optimization sub-problem. The original problem is reformulated as a mixed-integer second-order cone programming (MISOCP) problem. For GNO optimization sub-problem, an improved sequential cone programming (SCP) method is applied based on SOC relaxation and the original sub-problem is converted to MISOCP problem. A benchmark 6-node natural gas system and 6-bus electricity system is used to illustrate the effectiveness of the proposed framework. Considering pipeline congestion, CO, with demand response, can reduce the total cost of an electricity network by 1.19%, as compared to −0.48% using traditional decentralized operation with demand response.

This paper deals with experimental study and numerical simulation of single phase AC low power loads: artificial light sources, personal computers, refrigeration units, air conditioning units and TV receivers. These loads are in such large numbers that represents the main source of disturbances (harmonic current, reactive power and unbalanced three-phase network). The obtained simulation models, verified by comparison with experimental results may be used in larger simulation models for testing and sizing the optimum parameters of active power filters. Models can also be used to study the interactions between grid elements and various loads or situations.

Muscle functional MRI (mfMRI) is an imaging technique that assess muscles’ activity, exploiting a shift in the T2-relaxation time between resting and active state on muscles. It is accompanied by the use of electromyography (EMG) to have a better understanding of the muscle electrophysiology; however, a technique merging MRI and EMG information has not been defined yet. In this paper, we present an anatomical and quantitative evaluation of a method our group recently introduced to quantify its validity in terms of muscle pattern estimation for four subjects during four isometric tasks. Muscle activation pattern are estimated using a resistive network to model the morphology in the MRI. An inverse problem is solved from sEMG data to assess muscle activation. The results have been validated with a comparison with physiological information and with the fitting on the electrodes space. On average, over 90% of the input sEMG information was able to be explained with the estimated muscle patterns. There is a match with anatomical information, even if a strong subjectivity is observed among subjects. With this paper we want to proof the method’s validity showing its potential in diagnostic and rehabilitation fields.

Describes the method for calculating in complicated closed electrical networks. Mathematical description of the system is based on the use of graphs and matrices.

The Satellite Launch Vehicle electrical network, which is currently being developed in Brazil, is sub-divided for analysis in the following parts: Service Electrical Network, Controlling Electrical Network, Safety Electrical Network and Telemetry Electrical Network. During the pre-launching and launching phases, these electrical networks are associated electrically and mechanically to the structure of the vehicle. In order to succeed in the integration of these electrical networks it is necessary to employ techniques of electrical power distribution, which are proper to Launch Vehicle systems. This work presents the most important techniques to be considered in the characterization of the electrical power supply applied to Launch Vehicle systems. Such techniques are primarily designed to allow the electrical networks, when submitted to the single-phase fault to ground, to be able of keeping the power supply to the loads.

The problems of creation of monitoring system for electrical networks taking into account the quality of electric energy are considered in this article.

The increase of reliability of electrical networks can be achieved for example by use of new components. That modernisation is considerably expensive. Therefore close attention is paid to selection of new components and place of their position. The use of methods of multi-criteria analysis is suitable for this decision making.

Several online methods were proposed for investigating the voltage stability condition of an interconnected power system using the measurements of voltage and current phasors at a bus. For this purpose, phasor measurement units (PMUs) are used. A PMU is a device which measures the electrical waves on an electrical network, using a common time source (reference bus) for synchronisation. This study proposes a method for online monitoring of voltage stability condition of a power system using measurements of bus variables namely – (i) real power, (ii) reactive power and (iii) bus voltage magnitude at a bus. The measurements of real power, reactive power and bus voltage magnitude could be extracted/captured from a smart energy meter. The financial involvement for implementation of the proposed method would significantly lower compared with the PMU-based method.

The Satellite Launch Vehicle electrical network, which is currently being developed in Brazil, is sub-divided for analysis in the following parts: Service Electrical Network, Controlling Electrical Network, Safety Electrical Network and Telemetry Electrical Network. During the pre-launching and launching phases, these electrical networks are associated electrically and mechanically to the structure of the vehicle. In order to succeed in the integration of these electrical networks it is necessary to employ techniques of electrical power distribution, which are proper to Launch Vehicle systems. This work presents the most important techniques to be considered in the characterization of the electrical power supply applied to Launch Vehicle systems. Such techniques are primarily designed to allow the electrical networks, when submitted to the single-phase fault to ground, to be able of keeping the power supply to the loads.

We aim to generalize a theorem on the number of rooted spanning forests of a highly symmetric graph to the case of asymmetric graphs. We show that this can be achieved by means of an identity between the minor determinants of a Laplace matrix, for which we provide two different (combinatorial as well as algebraic) proofs in the simplest case. Furthermore, we discuss the connections to electrical networks and the enumeration of spanning trees in sequences of self-similar graphs.