kV Electrical Network Research Articles

THE OPTIMAL LOCATION OF RECLOSERS IN 10 KV AGRICULTURAL ELECTRICAL GRIDS

The agricultural networks are spread over a vast territory with a total length of more than 947 thousand kilometers. Their branching significantly affects the reliability of electricity supply and its quality. Improving the reliability of agricultural networks is an urgent task. It is advisable to use devices that allow automatizing the process of managing the electric network. Approximately 60 percent of the time is spent searching for the damaged area and restoring power to consumers connected to the undamaged sections of the circuit, 40 percent is spent searching for the place of damage and carrying out repair and restoration work. (Research purpose) The research purpose is to determine the economic efficiency of installing reclosers in 10 kV electrical networks. (Materials and methods) The article considers examples of feeders before and after the partitioning switches. Optimization criteria were calculated for each option: annual undersupply of electricity; the number and duration of consumer outages. (Results and discussion) The article presents the calculations of the options, analyzes the results obtained. (Conclusions) In order to reduce the total annual undersupply of electricity, it is necessary to divide the outgoing line into separate sections by installing sectioning reclosers. In order to increase reliability, reclosers should be placed closer to the consumer. Due to the optimal installation of reclosers, there is a decrease in the number and duration of outages, and a decrease in the annual undersupply of electricity in the network by 52 percent. The use of reclosers in electrical networks of 6-10 kilovolts has proven to be a more effective method of increasing the reliability of power supply both technically and economically.

АНАЛІЗ РЕЖИМУ РОБОТИ ЕЛЕКТРИЧНОЇ МЕРЕЖІ ПРИ ОДНОФАЗНИХ КЗ НАПРУГОЮ 6-35 КВ

In three-phase electrical networks during the operation of power supply systems, damage to electrical equipment and difficult modes of operation are possible. Damage associated with insulation failure, rupture of wires and cables of power lines, personnel errors when switching, lead to a short circuit between the phases or on the ground. At a short circuit in a closed circuit there is a big current, voltage drop on elements of the equipment increases that leads to the general decrease in voltage in all points of a network and disturbance of work of consumers. Complex modes of operation of electrical networks occur, as a rule, as a result of accidents or after emergency shutdowns of equipment, with subsequent overloads and voltage deviations from the nominal values. And although these modes have been considered acceptable for some time, they create the preconditions for various types of damage and disorders in the operation of power grids. To ensure normal operation of electrical networks and prevent the development of accidents, it is necessary to respond quickly to changes in the mode of operation of the electrical network, immediately separate damaged equipment from serviceable and, if necessary, turn on a backup power supply. These functions are performed by relay protection and automation devices. Principles of operation of relay protection devices. 1. Current protection. Short circuits are accompanied by a sharp increase in current that exceeds the value predetermined by the calculation, which will perform simple relay protection devices that can control the value of currents. Separate the maximum current protection, which acts to disconnect the damaged network element with a time delay and current cut-offs, which operate without a time delay. The difference between them is in the choice of how to ensure selectivity. The currents controlled by the relay protection device can be measured in phases (through current transformers), or individual components of phase currents can be measured (currents of direct, reverse and zero sequences. This method is based on the method of symmetrical components). Current types of protection are divided with control of power direction (directional) and without control (non-directional). Current protection works on the principle of operation not only in case of damage to one of the network elements, but also to adjacent ones. Therefore, current protection is referred to as protection with relative selectivity. 2. Differential protection. The basis of the principle of differential protection is the comparison of homogeneous, instantaneous values at the ends of the protected element of the network (transformer, busbar section, generator, overhead line). Usually compare currents in magnitude and phase. Differential protection by its principle works only in case of damage to the protected element of the network, so it is performed without time delay and differential protection is called protection with absolute selectivity. 3. Remote protection. In the event of short circuits in the electrical network is not only a sudden increase in current, but also a sharp decrease in voltage, ie a decrease in resistance. The advantage of relay protection devices based on this principle is that the resistance to the fault does not depend on the current and voltage, but only on their ratio. This allows protection at short-circuit currents less than the nominal for electrical equipment. Single-phase earth faults account for about 70% of all damage to electrical equipment. According to the Rules of technical operation in the event of a single-phase short circuit to "ground" in 6-35 kV electrical networks, relay protection devices must act either to turn off the equipment or to "signal". At the enterprises with special working conditions and the increased risk of damage of the equipment and defeat of people by action of an electric current protection against single-phase short circuits on the earth operates on shutdown with the minimum endurance of time. Thus, after the analysis of the modes of operation of power supply systems, the importance of using switching devices of relay protection to ensure normal operating conditions of electrical networks and prevent accidents is confirmed. Also, the use of relay protection devices must be justified for each individual electrical equipment according to the principles of operation and characteristics of the proper functioning of the switching apparatus. In case of emergencies, namely single-phase earth faults, 6-35 kV electrical network operation modes and operation of single-phase earth fault protection are performed according to various technical parameters, depending on the type and connection scheme of the neutral of this power system.

ПЕРЕНАПРУГИ ПІД ЧАС ДУГОВИХ ОДНОФАЗНИХ ЗАМИКАНЬ НА ЗЕМЛЮ В ЕЛЕКТРИЧНИХ МЕРЕЖАХ 35 КВ

The results of the study of overvoltages during arc single-phase earth faults of intermittent nature in the 35 kV electric network with isolated neutral are presented. Computer simulations of transients in the electrical network have obtained the maximum multiplicities of overvoltages at the point of occurrence of single-phase arc earth faults, which exceed theoretically expected according to known theories of the occurrence and development of overvoltages. 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, and the influence of the cable line on the overvoltage multiplicity are shown. Ref. 12, fig. 3, table.

On the choosing the installation location the balancing devices in low-voltage distribution electric networks

The experimental studies result on the power quality and additional power losses analysis caused by the asymmetric modes occurrence in three-phase four-wire 0.38 kV electrical networks are considered. The operating modes 38 kV networks several types simulation – with power take-off nodes distributed along the power line, and an electric network with a concentrated load is carried out. The programs have been developed that allow to assess the change in indicators characterizing asymmetric modes, as well as programs that allow us to visualize this process change. The most installing special symmetrical devices appropriate places in electric networks with a distributed load (rural electric distribution networks) and concentrated power take-off nodes electric networks (urban electric networks) have been identified to minimize losses and improve the power quality. A numerical studied indicators analysis was performed.

On the Rural Electric Networks Reliability Level Issue

The structure study, condition and 10 kV electric networks reliability level in the Irkutsk region for the period from 2016 to 2020 is carried out. The analysis is based on real data on the studied electric networks published in the open press. The Interactive Matlab system libraries and interfaces were used to calculate and analyze the studied indicator. The considered electric networks structure has investigated, algorithms and computer programs for the Matlab graphic editor are compiled with the help which changes time diagrams in the failures number, the interruptions time and the under-output electricity amount for each year months are constructed. The year months in which the highest damage occurs were determined. The electrical networks wear is considered, as well as the repair plan implementation for the main equipment. The reliability level according to the established indicators has analyzed, the main reasons for equipment failure are considered. The characteristics of improving considered electrical networks functioning are presented. Based on the conducted studies, it was found that the most damaged the considered overhead lines elements are: wires, supports, insulators, and switching devices. The characteristic reasons that lead to their damage are: wind load, damage to switching devices. The greatest damage is the Angarsky and Irkutsky branches networks characteristic (the average annual value all failures are 26.4 and 23.9%). The Kirensky and Cheremkhovsky branches networks are the least damaged annually. The obtained data probabilistic-statistical and correlation analysis, as well as the emergency outages risks analysis for the future, taking into account the seasonal component, is carried out.

Method for automatic compensation of a single-phase earth fault

The paper demonstrates improving the reliability of power supply and operating safety of power receivers in electric networks of 6-10 kV, by controlling the neutral mode in extended electric networks of 6-10 kV with capacitive earth fault currents above 15 A. The purpose of the study is to increase the reliability of power supply and the safety of operation of power receivers in such electric networks, the establishment of patterns in controlling the neutral mode in extended 6-10 kV electric networks with capacitive earth fault currents above 15 A, as well as the development of a method and device automatic detection of single-phase earth fault current. Grounding methods and neutral modes in electric networks with a voltage of 6-10 kV are considered. The method and device for automatically determining the current of a single-phase earth fault were developed. In the result, the relationship between the active and inductive components of the neutral current during series RL grounding of the network Ia/IL=(0.5÷0.3) was established, which ensures reliable operation of the SPEF protection of both current and directional principles including the changes of capacity abruptly networks caused by switching outgoing lines.

Improving the electric power quality in the networks adjacent to the railroad traction substations

A significant deterioration in the electric power quality indicators (EPQI) is observed in the 110-220 kV electrical networks, which are directly adjacent to the traction substations of the Trans-Siberian Railway. Such situations are typical of many regions of Siberia and the Far East. The article presents the results of research aimed at improving the electric power quality in the networks adjacent to the traction substations. The simulation algorithms used were based on application of phase coordinates and lattice equivalent circuits. Software tools Matlab and AnyLogic were used to model transition processes and evaluate the effectiveness of the concept of an intelligent electricity quality controlling system. On the basis of the results, technical solutions have been proposed to bring the electric power quality indicators to standard values. It is shown that a comprehensive approach, including the following segments, is needed to address the problem of reduced electric power quality: the use of technology to improve electric power quality indicators; reinforcing 110-220 kV networks that feed traction substations; technologies of smart customization and control of technical means.

Estimation Method of the State of 6-10 kV Distribution Network

The article analyzes the state of the elements of 6-10 kV distribution electrical networks in Dushanbe, showing the excess of reliability and efficiency indicators of the considered electrical networks from the permissible 10% values. For the first time, the factors influencing the reliability indicators of 6-10 kV electrical distribution network elements in Dushanbe were identified and a mathematical model of networks for determining the state of 6-10 kV electrical distribution network elements in Dushanbe was proposed. On the basis of them, an algorithm for monitoring the state of the elements of 6-10 kV electrical distribution networks in Dushanbe is proposed, which makes it possible to evaluate the efficiency of 6-10 kV distribution electrical networks in terms of undersupply of electricity - ΔW.

ANALYSIS OF VOLTAGE NON-SINUSIDALITY IN POWER SUPPLY SYSTEMS WITH INDUCTION HEATING UNITS

The importance of the problem of improving the quality of electrical energy grew along with the development and widespread introduction of various high-performance technological installations in production, such as arc steel-making furnaces, welding installations, induction furnaces, etc. in accordance with the requirements of the standard GOST 30804.4.7–2013 and in accordance with the measurement program. A method for processing the research results obtained during the experiment is described. All power quality indicators are processed using computer programs created in the Labview graphical programming environment. The analysis of indicators of the quality of electrical energy to the requirements of GOST 32144-2013 was carried out, according to the results of which conductive low-frequency electromagnetic interference was detected in the 0.4 kV electrical network according to the coefficient of the n-th harmonic voltage components. The obtained values ​​of the indicators of the quality of electrical energy, characterizing the coefficient of the n-th harmonic components of the voltage, confirm the need to use technical means to reduce the influence of higher harmonics on electrical networks.

Improving the functioning efficiency of 6-10 kV electrical networks with isolated neutral in conditions of single-phase ground faults

The main objectives of this publication are: 1) to attract the attention of energy specialists to the problems of reliability and electrical safety of 6-10 kV overhead electrical networks with isolated neutral, operating in conditions of single-phase insulation damage; 2) substantiation of the feasibility of introducing a fundamentally new way to improve the efficiency of 6-10 kV distribution networks, based on the resonanceless limitation of the single-phase ground fault current arising from the breakdown of the insulator and the use of its own infrastructure of the electrical network for remote identification of the place of its occurrence. The expediency of including a nonlinear surge suppressor between the traverse and the grounding outlet of the reinforced concrete support is confirmed by the positive results of experimental studies carried out on the basis of high-voltage testing laboratories of IDGC of Center PJSC - Orelenergo and EnerGarant LLC. The use of deductive analysis allowed the authors to select a reliable and affordable electrical insulating material installed between the support and the traverse, as well as to formulate the main requirements for it, including taking into account weather and climatic factors. The analysis of various methods of transmitting information about the place of occurrence of the insulator damage made it possible to establish the predominant advantage of a wired communication channel using its own 6-10 kV electric network infrastructure. The authors have developed an original circuitry solution that provides remote identification of the insulator damage location using a thyristor shunting the nonlinear surge suppressor, according to a given switching algorithm, and also provides local identification of the insulator breakdown by means of special signaling devices with volatile power supply. It is expected that the proposed method, with relatively low investment, will significantly reduce the level of accidents and electrical hazards in overhead distribution networks of 6-10 kV, as well as minimize the costs associated with their operation and undersupply of electrical energy.

Учёт несинусоидального/несимметричного режима работы электрической сети коммунально-бытового назначения при расчете уровня тока нулевого проводника

During the operation of 0.4 kV electric networks, asymmetry of currents and voltages is unavoidable. As is known, unbalanced operation of 0.4 kV networks is stemming from nonuniform distribution of loads between the phases. This results in that a fundamental frequency zero-sequence current will flow through the neutral conductor in a four-wire three-phase electric network. On the other hand, during balanced operation of a four-wire electric network containing loads with a nonlinear volt-ampere characteristic, higher harmonic currents multiple to three are summed in the neutral conductor. Therefore, it is of relevance to analyze unbalanced operating conditions of a four-wire electric network containing loads with a nonlinear volt-ampere characteristic. The article presents the characteristics of a municipal load for analyzing unbalanced/nonsinusoidal conditions of its operation. For carrying out full-valued assessment of unbalanced operating conditions of a four-wire electric network, a simulation model of a 0.4 kV network section containing a nonsinusoidal load is developed. It is shown that during unbalanced operation of an electric network containing electric loads with a nonlinear volt-ampere characteristic it is recommended to take into account zero-sequence current higher harmonic components that are not multiple to three. An algorithm for calculating the neutral conductor current harmonic component for determining the cable temperature rating is developed.

Визначення оптимального значення опору резистора заземлення нейтралі в мережах 20 кВ

At present, there is an objective need for a solution in the power system of Ukraine problems of improving the principles of construction of network topology by voltage classes and types of performance on based on scientifically sound technical solutions using modern methods and technologies. The article is devoted to the study of the optimal value of the resistance of the neutral grounding resistor in 20 kV networks. Distribution electric networks of Ukraine with a voltage of 6 (10) kV are included in the final link systems of providing consumers with electric energy. They are in direct interaction both with the consumer, and regional and main electric networks. Therefore, the state and the operation of 6 (10) kV electrical distribution networks has a significant impact on performance reliability, quality and efficiency of the integrated power system of Ukraine. Transition from voltage level 6 (10) kV on 20 kV is an actual and priority step to increase the efficiency of operation distribution network and a significant reduction in electricity losses. The paper presents the types of resistors and options for their installation in the neutral voltage network 20 kV. The relationship between the resistance of the neutral grounding resistor and the single-phase current is established short circuit, which directly affects the types of relay protections, as well as their number. Simulation of the 20 kV network operation mode was performed, based on the results of which the optimal one was chosen the value of the resistance of the neutral grounding resistor in the presented network, which is achieved sufficient sensitivity of relay protection devices at the lowest short-circuit current. This one was chosen for the study neutral grounding method, because resistive grounding has the following advantages: no arcs high-frequency overvoltages and multiple damages in the network; no need to disconnect the first single-phase earth fault; reducing the likelihood of impressions of staff and outsiders at single-phase short circuit; almost complete exclusion of the possibility of transition of single-phase circuit to ground in multiphase; simple implementation of sensitive and selective relay protection single-phase ground fault.

Analytical method for determining the fault location in 10 kV electric networks by the equations of the 3rd degree relative to voltages

Analytical method for determining the fault location in 10 kV electric networks by the equations of the 3rd degree relative to voltages

Optimization of the grid configuration by the method of contour optimization

In the article the question of a choice of an optimum network by a method of contour optimization and calculation of operating modes of a network is considered. A 110/35/10 kV substation project has been developed. The basic and reserve protection of the power transformer is chosen. A startup project of the optimal scheme of power supply of consumers with 110 kV network has been developed. Measures and means have been selected to ensure safe working conditions during the operation of the 110 kV network. The function of discounted costs for an overhead line with a nominal voltage of 110 kV is formed. Actuality of theme. When designing one of the main tasks is to optimize the configuration of power grids to achieve the maximum possible economic-nominal effect, without violating these technical requirements. The purpose of work is to optimize the network by the method of contour optimization and calculation of network modes. Object of research: 110 kV electrical distribution network. Subject of research: network configuration optimization. Research methods. Methods of theoretical bases of electrical engineering and electric networks, mathematical modeling, numerical methods of solving nonlinear systems of equations.

Математические модели для определения предельных режимов в электрических сетях с установками распределенной генерации

Decentralization of electricity generation based on distributed generation plants is an important segment of the new technology platform for the power industry. On the basis of this approach, significant positive effects can be obtained, which consist in reducing financial costs of energy supply, increasing the uninterrupted power supply, improving the quality of electricity and stimulating the use of renewable energy sources. Effective use of distributed generation in electric power systems requires the development of methods and tools that provide coordinated management of normal, emergency and post-emergency modes. Of particular relevance is the problem of determining the limit operating modes of networks, at the nodal points of which relatively low power generators are connected. In some situations, for example, when using small hydraulic stations, groups of such generators can be located at significant distances for 6-10-20 kV distribution networks from consumption centers. In this case there will be a noticeable limitation of the regions of static aperiodic stability. The article presents the results of developments aimed at implementing methods for determining the limit operating modes by static aperiodic stability in networks with distributed generation plants. The proposed approach is based on the limit modes equations which provide the formation of effective algorithms for the operational finding of points belonging to the boundaries of stability regions. The results of the construction of the indicated areas for a 6 kV electric network with distributed generation plants based on low-power hydraulic stations are presented. Additionally, the transient processes in the studied electric power system were simulated in the Matlab system for various space points of the controlled mode parameters.

Wire Break Protection System for 0.38 and 6 – 10 KV Overhead Power Transmission Lines

Currently, there is no automation and protection equipment to detect wire breaks in 6 – 10/0.38 kV electric networks. A protection system based on microprocessor electricity meters installed in a 0.38 kV network for the automatic detection of a damaged section of 0.38 and 6 – 10 kV overhead lines is proposed. A functional diagram of the protection system is described.

A Procedure for Placing Shunt Reactors in High-Voltage Networks and Justification of its Efficiency

In recent years, the controlled shunt reactor (CSR), a type of FACTS device, has been widely used to regulate voltage and reactive power flows in the high-voltage electrical network. The selection of location and the determination of the law of CSR control under the stochastically variable operation of high-voltage power transmission lines are associated with numerous technical and economic factors. At the same time, one should take into account such limiting conditions as ease of use, performance, purpose, and location in the system, as well as the time of commissioning. In the proposed procedure, these factors are considered as fuzzy constraints. The paper proposes a procedure for CSR placement in the 330 kV electrical network of the “Azerenergy” system for control of reactive power flows, given the mentioned fuzzy constraints. The obtained simulation results demonstrate the advantage of the proposed procedure. The computational experiments confirm the CSR efficiency.

Выбор средств защиты высоковольтного двигателя экскаватора на руднике открытых работ горно-металлургического комбината

Based on the results of conducting comprehensive studies of power consumption of the open-pit mine of the mining and metallurgical plant in high altitude conditions, the issues are considered related to ensuring safe operation of electric motors supplying excavators. Experimental studies were carried out in a 6 kV electric network, from which the excavators and drilling rigs are powered. The design schemes of sections of the electric network are given, the characteristic of the main equipment is provided. One of the problems in the operation of the excavators in high altitude quarries is a decrease in their productivity due to the need in periodical repair of the insulation of synchronous motor drive of the converter unit. The influence of switching overvoltages on the synchronous motors insulation integrity of the excavator is established. The scheme of a protective device is presented, which allows protecting the isolation of the excavator engine from atmospheric and internal switching overvoltages. The principle of synthesis of the surge suppressor is to determine the maximum amplitude of free component of the switching voltage and the corresponding frequency with the subsequent installation of the quenching spark gap and the shunt capacitance, calculated according to a certain amplitude and frequency. Therefore, the main measure providing protection of the insulation of the drive motor should be the suppression of overvoltage, which has a fundamental frequency of 8–8.2 kHz. The network transient in the open-pit electric circuit — a synchronous motor is investigated, and the parameters of the shunt capacitor are determined. It was found that the selected capacitor is capable of long-term operation in an electrical installation at a frequency of 50 Hz. In order to reduce the effect of additional capacitance on the frequency, it is necessary to install capacitors together with the arresters in a 6 kV input cell.

ПОРІВНЯННЯ СТРУМІВ КОРОТКОГО ЗАМИКАННЯ ЕЛЕКТРИЧНОЇ МЕРЕЖІ 6(10) кВ та 20 кВ

The reasons for such violations are various: aging of insulation, breakages of wires of overhead transmission lines, mechanical damages of isolation of cable lines at ground works, lightning strikes in the transmission line and others. Most often, short-circuits occur through transient resistance, such as through the resistance of an electric arc that occurs at the point of damage to the insulation. Sometimes there are metallic short circuits in which the resistance of the electric arc is very small. The study of short circuits in the power grid is a major step in the design of modern electrical networks. The research is conducted using computer software, first by modeling the system and then simulating errors. A malfunction usually leads to an increase in the current flowing in the lines, and failure to provide reliable protection can result in damage to the power unit. Thus, short-circuit calculations are the primary consideration when designing, upgrading, or expanding a power system. The three-phase short circuit is the least likely. However, in many cases, the three-phase short circuit is associated with the most severe consequences, as it causes the highest power imbalances on the shafts of the generators. The study of transients begins with the mode of three-phase closure due to its relative simplicity in comparison with other types of asymmetry. In most cases, the analysis and calculation of the transient regime of the electrical system involves the preparation of a calculated scheme of substitution, in which the parameters of its elements are determined in named or relative units. The electrical substitution circuitry is used to further study the transients in the power system. The definition of electrical and electromagnetic quantities in relative units is widely used in the theory of electric machines. This is because it significantly simplifies the theoretical calculations and gives the results a generalized view in the practical calculations of currents and residual voltages at the short circuit. By the relative value of any value is understood as its relation to another value of the same name, taken as the base. So, before presenting any quantities in relative units, we need to choose the basic units. In the electrical system with increased voltages, the overall load capacity of the network increases, which in turn makes it possible to supply high-quality electrical energy over a greater distance. In the process of comparing the type of transmission lines, it should be noted that the advantages of the cable transmission line. According to the results of the calculation of short-circuit currents, it can be concluded that in networks with a larger line cross-section and a higher voltage, the short-circuit currents are larger. Thus, during the transition of the electric networks to the higher voltage class of 20 kV, the currents of the KZ increased by 43% compared to the 6 kV electric network. This analysis shows that the importance of reliable power supply in the power supply system for high voltage classes must be high and have equipment to prevent emergencies. In the future, it is planned to develop a systematic calculation of short-circuit currents for a number of transmission lines and to conduct mathematical modeling in the system of applications for the study of transient processes at short circuits

Determination of electromagnetic effects of electric traction networks on pipelines

The article presents the simulation results of electromagnetic effects of a 25 kV electric traction network on a steel pipeline with a pipe diameter of 250 mm. It is shown that a pipeline with insulating pipe coatings can induce stresses dangerous to operating personnel. At certain points of the pipeline, grounded on both sides, the magnitude of the induced voltage can reach 116 V with an approach width of 100 meters. Therefore, it is required to develop and implement special measures to protect operating personnel. With an increase in the approach width to 400 m, the maximum values of the induced voltages did not exceed the permissible level. In modes of short circuits in the electric traction network, the induced voltages in the pipeline may briefly exceed 500 V. The highest voltages are observed at points located near the short circuit point. In case of short circuits at the terminals of the traction substations, the magnitudes of the induced voltages are reduced to 75 V. To reduce the induced voltages, the following measures can be assumed: reducing the length of parallel passage sections of pipeline and railway, increasing the approach width, installing additional groundings. During the operation of the structure, the magnitude of the “pipe-to-ground” transition resistance may decrease, which will result in a decrease in induced voltages.