Emergency Mode Research Articles

Neural network in a “sliding window” for power grids signals structural analysis

In electric power systems, intelligent electronic devices monitor the state of an energy facility in real time. The data for monitoring the quality of electricity at the intelligent electronic device is transmitted through current and voltage measuring transformers. The operating modes, when the power transformer is turned on under voltage, as well as in emergency modes, signal distortions occur in the transformer. This paper is concerned with simplest feed forward artificial neural network to estimate the parameters of a distorted signal. The neural network is used to estimate the parameters of the current signal in the secondary winding of the current measurement signal. It is shown that the error in determining the parameters of the current is a few percent. The neural network requires a short time to operate, which potentially allows the use of neural network algorithms in intelligent electronic devices to process current and voltage signals in real time.

Electromagnet with magnetic memory for controlling vacuum contactors for rated currents of 160, 250, 400 A

The results of the development of a universal control circuit for a triggering polarized electromagnet for a low voltage vacuum contactor are presented. The circuit is implemented in the form of a printed wiring block and is unified with an element base with a control circuit for the KV2-160, KV2-250 vacuum contactors commercially produced by the domestic industry. The developed design of an electromagnetic drive with magnetic memory based on high-coercive permanent magnets is described. The working cycle of an electromagnet with a ferromagnetic shunt for the implementation of a manual return unit for the purpose of its use in emergency or necessary technological modes is considered. A block for manual return of contacts of a vacuum contactor using an eccentric transmission has been developed and implemented, which makes it possible to significantly reduce the effort of manual operation when returning the shunt to its original position for the operation of the contactor in normal mode. The classical graphical-analytical method for calculating magnetic circuits with permanent magnets has been modernized. The fundamentals of the modernized method for calculating magnetic circuits with permanent magnets are considered. The positive results of approbation of the developed calculation methods, which were implemented in the development of a vacuum contactor with magnetic memory and the function of manual return of the electromagnet armature and opening of the main contacts for the serial production of contactors, are noted.

Simulation of an Electric Drive with an Induction Motor in Emergency and Abnormal Modes of a Frequency Converter

Simulation of an Electric Drive with an Induction Motor in Emergency and Abnormal Modes of a Frequency Converter

CURRENT PROBLEMS OF PROVIDING FREQUENCY AND POWER REGULATION RESOURCES TO IPS OF UKRAINE

The main requirements for the volume of ancillary services in the IPS of Ukraine are considered. In particular, the requirements for the frequency maintenance reserve and frequency recovery reserves. The influence of renewable energy sources (RES) on the balance of production and consumption of electricity is shown. The place of hydroelectric power plants in the modern conditions of functioning of the IPS of Ukraine and the structure of the ancillary services market is considered. It is shown that in fact, according to the existing structure of production facilities in the IPS of Ukraine, only HPP and HPSP units are able to balance the fast-changing load schedule of renewable energy sources due to their high maneuverability. Features of operation of HPP units in normal and emergency modes are given. Prospects for the development of ancillary services in the IPS of Ukraine are identified. The need to update the regulatory framework was noted according to the results of the analysis of the peculiarities of the functioning of the IPS of Ukraine,. It is noted that it is necessary to clarify the Transmission System Code in terms of updating the requirements for the minimum required reserves for frequency control in the IPS of Ukraine given the growing share of unregulated RES in the structure of production capacity. Some measures are proposed to increase the level of operational security of regimes in the conditions of further development of RES and plans for synchronization of UES of Ukraine with ENTSO-E energy systems.

TRANSIENT ANALYSIS IN THREE-PHASE ELECTRICAL CIRCUITS WITH DISTRIBUTED PARAMETERS AND INTERFACIAL CONNECTION ON THE EXAMPLE OF HIGH-VOLTAGE CABLE LINE

The analysis of transients in three-phase electric circuits is carried out, which allowed to consider changes of transient components of currents and voltages of each phase of three-phase cable power line and to estimate the level of overvoltage and amplitude of short-circuit currents in screens taking into account transposition. Using the MatLab/Simulink program, software tools and methods for numerical calculation of transient electromagnetic processes in the designed 330 kV cable line were developed to analyze the level of voltages on the screens and currents in the cable cores at different switching modes. The calculations of a specific 330 kV cable line with a length of 13 km, laid for the first time in Ukraine for the power supply of the electric steel complex, were carried out. The calculation of the emerging transient electromagnetic processes in such a line under different conditions of its connection to the three-phase power supply network is carried out. Many types of switching overvoltages are subject to limitation. Feasibility studies of overvoltage protection measures include assessment of statistical characteristics of damage due to damage, simple or extraordinary repair of electrical equipment of the cable line, as well as due to violation of the technological process by consumers. The above determines the relevance of modeling and analysis of electromagnetic processes that occur when connecting and switching cable lines in ultra-high-voltage three-phase electrical circuits. This allows us to recommend the results of work to develop methods for determining the allowable and emergency modes of similar three-phase cable transmission lines and the choice of rational circuit design solutions in their design. Analyzing the transients in the mode of single-phase short circuit, we can conclude that to select the optimal lengths of the transposition sections of cable screens, it is necessary to consider single-phase short circuit mode, as in this mode there are unacceptable overvoltages on cable screens and currents in three-phase cable lines.

Analysis of Control Methods for the Traction Drive of an Alternating Current Electric Locomotive

The analysis of operating conditions of traction drives of electric locomotives with asynchronous traction motors has been carried out. It was found that during operation in the output converter of an asynchronous motor, defects may occur, which leads to asymmetric modes of its operation. Models of a traction drive of an electric locomotive with asynchronous motors with scalar and vector control of the output converter are proposed, taking into account asymmetric operating modes. As a result of the simulation, the starting characteristics of the traction drive were obtained for various control methods both in normal and emergency modes of the drive. For the drive-in emergency mode, the following cases were investigated: the balance of the converter output voltages and the turn-to-turn circuit of 10% of phase A winding of the motor stator; imbalance of the output voltages of the inverter and an intact motor; imbalance of the output voltages of the converter and interturn short circuit of 10% of phase A winding of the motor stator. Comparison of the simulation results have shown that in emergency modes in the traction drive, the torque ripple on the motor shaft in the drive with vector control is 13% less, and in scalar control, the phase current unbalance coefficient is 22% less. The results of this work can be used to study the influence of the output converter control methods on the energy efficiency indicators of the traction drive of an AC electric locomotive.

The study of the isolated power supply system operation with controlled distributed generation plants, energy storage units and drive load

THE PURPOSE. Investigation of the operating modes of an isolated power supply system with controlled distributed generation plants, energy storage units and a drive load. Determination of the influence of the proposed prognostic controller of a distributed generation plant on the control parameters and quality indicators of the control process under various operating modes of an isolated power supply system.METHODS. The studies were carried out on a computer model of an isolated power supply system of an industrial enterprise with a turbine generator plant, a wind generator plant and a high-power electric storage unit, for which a fuzzy control system and a prognostic controller were used. The simulation was performed in MATLAB using Simulink and SimPowerSystems packages.RESULTS. The article describes a computer model of an isolated power supply system, as well as a structural diagram of the proposed autoprognostic speed controller. The simulation results showed that the combined use of an energy storage unit and an auto-prognostic generator rotor speed controller makes it possible to ensure the stability and survivability of an isolated power supply system, increasing its damping properties. The use of a fuzzy control system of a wind-generating plant made it possible to ensure its stable operation in all considered modes.CONCLUSION. The auto-prognostic speed controller, which does not require special settings, and the energy storage unit provide high quality control indicators in normal and emergency modes. It is advisable to conduct further studies to coordinate the actions of the control system of the electric energy storage unit and the auto-prognostic speed controller of the distributed generation plant.

Short circuit fire risk assessment in investigating and examining fires caused by emergency modes in overhead transmission lines

Emergency modes (short circuits) in electric power system and equipment are the main technical cause of fires. However, it is not always possible to prove the involvement of a particular operating mode in a fire. The fire hazard can be due to three components: a fuel load, an oxidizer and an ignition source. Since overhead transmission lines are used in an open space, they are oxidized. The presence of a fuel load is confirmed by a fire. The source of ignition should be identified. The aim of the study is to develop an algorithm for assessing the fire hazard for short circuits in overhead transmission lines with 1000 V. The study was conducted using scientific analysis, physical experiment and simulation. The ignition source is due to the appearance of an energy source with parameters sufficient to ignite a fuel load. The probability of ignition in overhead line wires depends on the probability of occurrence of the short circuit itself ( Qi (v1) ) , the probability of failure of protection devices ( Qi (v2) ), and the probability that the electric current value in the event of a fault is in the range of fire hazard values (Qi(z)). The values of the first two components are determined on the basis of statistical data, taking into account the theory of reliability. The third component is based on the experiment results. The experimental studies made it possible to establish the ranges of fire hazard values for uninsulated aluminum wires of various cross-sections, thereby providing the possibility of calculating ( Qi (z). Using the data obtained and information about the nature of changes in short-circuit currents and performance characteristics of protection devices, depending on the line length, an algorithm for assessing the fire hazard for a short circuit was developed. The results make it possible to assess the fire hazard for short circuits in various sections of the electrical network, made by overhead transmission lines, and to establish the involvement of sparks generated by short circuits in a fire

Applications of ash аnd slag waste in agriculture

Environmental pollution creates problems for health of people living in residential areas near pollution sources. Studies aimed at developing methods for investigating the impact of industrial facilities on the air is of interest. The purpose of this work is to analyze the methodology for assessing the risk of exposure of a technosphere object to the atmosphere. It was assumed that the enterprise in emergency mode emits pollutants through the source of emissions at the maximum single concentration of the substance exceeding the maximum permissible concentration. To calculate the impact on a human, various scenarios of an emergency situation are taken into account. These are constructing failure trees and using well-known health risk assessment techniques. The calculation took into account the wind rose for a specific enterprise location and wind speed projections obeying the normal distribution law. These assumptions allowed us to develop a method for calculating the risk of exceeding the concentration of a pollutant at a given point (x, y) during the year. Isolines of surface concentrations were built. Three toxic substances were taken for analysis. The method for calculating the dispersion of emissions of harmful (polluting) substances in the atmospheric airwas used; maps of the dispersion of isolines of pollutants in residential areas were constructed. When solving the inverse problem, emergency emission intensities at which excess of permissible concentrations occurred were determined. In the range of multiplicities exceeding the maximum single maximum permissible concentration from 1 to 5, the dependence was well approximated by a straight line. This technique can be used to determine the risk of diseases caused by carcinogenic and noncarcinogenic substances and minimize the risk of exposure to harmful substances. Ash and slag wastes are the source of negative impact on the environment. This area is studied by a number of researchers. The article aims to systematize the data on possible applications, accumulated practical experience of using ash and slag waste in agriculture both in Russia and abroad. The analysis showed that waste from the fuel and energy industry can be widely used in various areas of agriculture. It can be used as ameliorants, zeolite-based mineral fertilizers, pesticides and insecticides for treating horticultural crops, microfertilizers, as well as for soil remediation and land reclamation. The use of ash and slag waste in agriculture and other sectors of the national economy can reduce the ecological load on the environment. The number of overfilled ash dumps can be reduced, and there will be no need to build new ones.

Risk assessment for the industrial facility impact on the atmosphere

Environmental pollution creates problems for health of people living in residential areas near pollution sources. Studies aimed at developing methods for investigating the impact of industrial facilities on the air is of interest. The purpose of this work is to analyze the methodology for assessing the risk of exposure of a technosphere object to the atmosphere. It was assumed that the enterprise in emergency mode emits pollutants through the source of emissions at the maximum single concentration of the substance exceeding the maximum permissible concentration. To calculate the impact on a human, various scenarios of an emergency situation are taken into account. These are constructing failure trees and using well-known health risk assessment techniques. The calculation took into account the wind rose for a specific enterprise location and wind speed projections obeying the normal distribution law. These assumptions allowed us to develop a method for calculating the risk of exceeding the concentration of a pollutant at a given point (x, y) during the year. Isolines of surface concentrations were built. Three toxic substances were taken for analysis. The method for calculating the dispersion of emissions of harmful (polluting) substances in the atmospheric airwas used; maps of the dispersion of isolines of pollutants in residential areas were constructed. When solving the inverse problem, emergency emission intensities at which excess of permissible concentrations occurred were determined. In the range of multiplicities exceeding the maximum single maximum permissible concentration from 1 to 5, the dependence was well approximated by a straight line. This technique can be used to determine the risk of diseases caused by carcinogenic and noncarcinogenic substances and minimize the risk of exposure to harmful substances.

Synchronization of multi‐machine power systems under disturbances and measurement errors

SummaryThe problem of multi‐machine power system synchronization under parameter uncertainties, emergency modes, and measurement errors is considered. Only power angles of generators corrupted by bounded measurement errors are available for measurement. Emergency modes are associated with the sudden change of reactance of transmission lines. The proposed control law is based on measurement error filtering and left‐differences estimation of power angel derivatives. Differently from some recent control schemes, it makes the obtained control law easier to tune and less sensitive to measurement errors. The robust‐adaptive control law is suggested under unknown nominal values of reactances, EMFs, and currents. The simulations and experiments illustrate the efficiency of the proposed algorithm and confirm theoretical results in comparison with some existing ones.

The application of pre-hospital first aid mode in patients with acute stroke: meta-analysis.

To systematically evaluate the application effect of pre-hospital and in-hospital emergency mode in patients with acute stroke. The study was conducted by systematic search of Chinese (CNKI, Wanfang and VIP) and English (PubMed, EMBASE and Cochrane Library) databases. The case-control studies comparing the role of pre-hospital and in-hospital emergency mode for patients with acute stroke were included in this study. Outcome indicators included the time from admission to thrombolytic therapy (DNT), the time from calling for help to receiving professional treatment, the first aid effect (effective rate, disability rate and mortality), complications and prognosis. Meta-analysis was performed using RevMan 5.3. Seventeen studies were included in the final analysis. Compared with traditional emergency measures, pre-hospital and in-hospital emergency measures can significantly reduce DNT (mean difference [MD] = -22.63, p < 0.00001), time from call to professional treatment (MD: -13.22, p < 0.00001), disability rate (RR = 0.88, p = 0.004), fatality rate (RR = 0.58, p < 0.00001), central cerebral fever (RR = 0.44, p = 0.0009), and gastrointestinal bleeding (RR = 0.44, p = 0.002). In addition, daily living ability (MD = 16.56, p < 0.00001) and emergency response rate (RR = 1.50, p < 0.00001) were significantly improved. The pre-hospital and in-hospital emergency mode has a significant emergency effect in patients with acute stroke, which is a protective factor. This emergency mode can be widely used in clinical practice.

ОЦЕНКА УСТОЙЧИВОСТИ СИНХРОННЫХ ДВИГАТЕЛЕЙ В ПЛОСКОСТИ ДВУХ УГЛОВ

Relevance The main technological installations of the oil and gas industry require power supply of the first category and are fed from two independent sources. Possible short-term interruptions of power supply of such installations by their duration should not lead to a violation of the stability of electric motors and disruption of technological processes. The problem of stability at enterprises equipped with automatic standby switching devices with self-starting of synchronous motors after a short interruption of power supply is especially relevant. Therefore, the assessment of conditions for preserving the dynamic stability of synchronous motors after a short interruption of power supply is an urgent task. Aim of research Based on the method of areas, develop a method for assessing the dynamic stability of synchronous motors in the plane of two parameters. Methods The article uses dynamic stability areas in the plane of two angles to assess the dynamic stability of synchronous motors: the load angle of the synchronous motor in the pre-emergency mode δ0 and the inclusion angle δвкл between the mains voltage vectors and the residual voltage on the section that lost power, in the emergency mode. Results The dynamic stability area in the plane of two angles is plotted: the load angle δ0 and the turn-on angle δвкл. The boundary lines of dynamic stability area are plotted for the range of values of load angles, in which the static stability of the synchronous motor in the pre-emergency mode is preserved. On the example of synchronous motor of STD-2500 type, the definition of the dynamic stability area in the plane of parameters under study is shown. It is shown that the region of dynamic stability in the plane of two angles can be transformed into the dynamic stability area of other investigated parameters.

ИССЛЕДОВАНИЕ ОДНОФАЗНОГО ЗАМЫКАНИЯ НА ЗЕМЛЮ В ЭЛЕКТРИЧЕСКИХ СЕТЯХ 6-35 КВ С ИЗОЛИРОВАННОЙ НЕЙТРАЛЬЮ

Ground faults in networks with an isolated neutral are not switched off by relay line protections due to low capacitive currents. It is recommended to disconnect the line with a earth fault as quickly as possible, but sometimes it is difficult to find and localize the damage. To analyze the emergency mode of single-phase ground fault in networks with an isolated neutral, the phase coordinate method for calculating phase voltages is used. At the point of damage, the values of the phase-to-phase voltages remain unchanged, and the phase voltages change. Real research and analysis of electrical network modes of 6-35 kV with an isolated neutral is rather time-consuming task. Therefore, the calculation of phase voltages at the substation during an earth fault is carried out through the transition resistance on the line based on the phase coordinate method. The authors developed a virtual model of studied power transmission line for analyzing asymmetric modes of three-phase networks and checking the operability of the method in the MATLAB Simulink simulation package. The simulation results showed that there was no discrepancy between the voltage and current values of the original model in phase coordinates and the Simulink model. As a result of the research, the authors have found that the phase coordinate method helps calculate emergency modes with the overlay of several component accidents taking into account load currents. The model in phase coordinates will allow analyzing relay protection operation at high speed under different operating modes of the electric power system.

О возможности использования упрощенных моделей для определения места утечки в газопроводе

For gas transportation through pipes in normal and emergency modes, a comparison of calculations based on mathematical models of various degrees of generality is presented. A mathematical model of a non-isothermal steady flow of a mixture of gases and its simplified versions are studied. For simplified options, simple analytical dependencies were obtained for calculating flow characteristics and calculating the location of an emergency gas leak. Examples of calculations of pressure distributions, temperature and leakage coordinates in gas pipelines of medium pressures according to the general and simplified models are provided. The examples cover the parameter change area of practical interest. The conditions for the admissibility of using simplified models for calculating the coordinates of a leak of medium intensity and different locations are determined.

Моделирование феррорезонансных режимов в нелинейных электрических цепях с учетом магнитного гистерезиса

Приведено решение задачи численного моделирования феррорезонансных режимов напряжений и токов в электрических цепях, возникающих при последовательном и параллельном соединении нелинейного индуктивного и емкостного элементов. Вебер-амперная характеристика индуктивного элемента задана с учетом гистерезиса. Известно, что феррорезонансные режимы возникают в электрических цепях, содержащих емкостные и нелинейные индуктивные элементы, в том числе силовые трансформаторы, дугогосящие реакторы, измерительные трансформаторы тока и напряжения, электродвигатели. Нелинейность характеристик индуктивных элементов служит причиной того, что при насыщении их магнитных систем происходит изменение дифференциальных индуктивностей, в результате возникают феррорезонансные, часто нештатные и даже аварийные режимы. Для имитационного моделирования магнитного гистерезиса использована модифицированная обратная модель Джайлса-Атертона. Численное интегрирование дифференциальных уравнений, описывающих динамические процессы в электрических цепях, выполнено явным методом Эйлера. Показано, что в результате феррорезонанса возникает тригеррный эффект, проявляющийся в форме скачкообразного изменения состояния цепи, вызванного неоднозначным характером вольт-амперной характеристики для входного напряжения и тока. Предложенный метод моделирования переходных и установившихся режимов в нелинейных электрических цепях с учетом магнитного гистерезиса может быть обобщен на случай произвольных цепей, в том числе, со сложной топологией.

Estimation of possibilities of calculations based on simplified models of the leak location in gas pipelines

For gas transportation through pipes in normal and emergency modes, a comparison of calculations based on mathematical models of various degrees of generality is presented. A mathematical model of a non-isothermal steady flow of a mixture of gases and its simplified versions are studied. For simplified options, simple analytical dependencies were obtained for calculating flow characteristics and calculating the location of an emergency gas leak. Examples of calculations of pressure distributions, temperature and leakage coordinates in gas pipelines of medium pressures according to the general and simplified models are provided. The examples cover the parameter change area of practical interest. The conditions for the admissibility of using simplified models for calculating the coordinates of a leak of medium intensity and different locations are determined. Keywords: gas pipelines, adequacy of the model, simplifications, calculation of the place of emergency leakage, compressibility factor.

Моделирование механической характеристики асинхронного двигателя

Рассмотрены вопросы моделирования механической характеристики асинхронных двигателей для построения динамической системы машинного агрегата. Использована упрощенная формула Клосса для построения механической характеристики по каталожным данным двигателей. Представлены методы ее корректировки для возможного использования в пусковых, переходных и аварийных режимах. Процесс моделирования осуществлен аналитически и реализован численно в символьном пакете Mathcad. Установлена связь между параметрами электромеханической системы и угловой скоростью вала двигателя методом параметрического моделирования. Выполнен сравнительный расчет механической характеристики по приближенной и уточненной формуле.

Investigation of induction motor operation from the soft starter in reverse mode with reduced speed

Ease of maintenance and high reliability of asynchronous electric drives actively popularize their using in manufacturing. At the same time, such drive has its drawbacks: high currents and significant torque during direct starting from contactor control systems. This problem can be solved using the so-called "service functions" of soft starters. This work at developing these functions and issuing recommendations for their use is aimed. The purpose of the investigation is to determine the possibility of using the "service functions" of soft starters for emergency and service modes of agricultural plants. The investigation of the operation of an induction motor with a soft starter using the provisions of the theory of electrical circuits of sinusoidal and non-sinusoidal currents and using computer analysis was carried out. Investigation on the mechanism of straw shredders using a soft starter was carried out. Performance increasing of such a mechanism is possible using the "reverse" function with a reduced speed, implemented, for example, in SSW900 soft starters. To configure the soft starter, the WEG programming Suite software was used, which, in addition to the function of writing parameters, also contains the function of reading parameters and visualizing them as trends. As a result of the investigation, it was found that the intelligent control of thyristors in soft starters allows to expand their functionality, namely, to reverse the induction motor without using an additional contactor. The implementation of the reverse speed function with appropriate restrictions in soft starters allows reducing the cost of the used electrical equipment for straw shredders. Too much JOG relative voltage to the soft starter can cause large fluctuations in motor speed and must be carefully adjusted.

Feasibility Study for Project of Agrophotovoltaic System Based on the Existing Solar Power Plant

The object of the research is an agrophotovoltaic system. An analysis of the operating conditions of one of the existing solar power plants was performed and limitations of electricity generation due to its excess in the power system or due to work mode restrictions both under the normal state of the power grid and under individual emergency or repair modes were identified. This leads to an underproduction of electricity and a decrease in the efficiency of using the installed capacity of the solar power plant (SPP). Therefore, it was proposed to introduce an agrophotovoltaic system, which allows for more efficient use of land resources, it also allows us to increase the yield of agricultural crops that can be planted on the territory of a solar power plant, to eliminate restrictions on the delivery of generated power to the power grid through its direct consumption at the site of the SPP. The feasibility study of the project of an agrophotovoltaic system based on the existing power plant shows that its payback period will not exceed 3 years, and the profit for the 5th year of exploitation of such a system will be up to € 279409.