Features of asymmetric short circuit currents calculation in the elplek software product

2021 ◽  
pp. 113-127
Author(s):  
O. Gai ◽  
◽  
V. Bodunov ◽  
A. Zhiltsov ◽  
◽  
...  
Keyword(s):  
Power Systems ◽  
Short Circuit ◽  
Active Part ◽  
Electrical Network ◽  
Electrical Networks ◽  
Software Products ◽  
Software Product ◽  
Short Circuits ◽  
Infinite Power ◽  
Short Circuit Currents

In order to simplify the analysis of the electrical networks operation modes , specialized software tools for mathematical modeling of processes in them are used. There are many software products, but most of them are paid. To carry out research in complex power systems and obtain results in certain sections when performing practical and course work, as well as at certain stages of research, the authors actively use the free software product «Elplek», but in a deeper study of the software encountered certain features some parameters, which differ slightly from the generally accepted domestic method, which led to an error in the calculations in some versions of the schemes of power systems. The purpose of the research is to study the peculiarities of calculating the characteristics of asymmetric short circuits in the software product "Elplek" and to check the adequacy of the formed models. At the first stage, the object of research was chosen – this is a segment of the electrical network containing a small number of nodes and a theoretical calculation of the searched parameters of the short circuit mode in this segment of the electrical network was carried out. In the future, an approach was proposed on the task of parameters of elements in the software product "Elplek" and based on this approach, modeling was carried out as a result of which the results were obtained under the condition of the system's task, as sources of infinite power and calculations for the active part differ by 0.013%, and by reactive – 0.004%; subject to the task of the system, as sources of a certain power and calculations on the active part differ by 0.0046%, and on the jet - 0.0044%, which makes it possible to assert the feasibility of using the proposed approach in the analysis of indicators of emergency modes of complex schemes of electrical supply to consumers of certain segments of electric power systems. Features of calculation of characteristics of asymmetric short circuits in the Elplek software product are considered and the adequacy of the generated models is checked. Key words: power system segment modeling, Elplek software product, element parameter setting, single-phase short-circuit currents

Investigation of dependences of selectivity of devices of protection against the value of short circuit currents in electrical networks up to 1000 V

2021 ◽  
pp. 98-100
Author(s):  
I. Radko ◽  
◽  
V. Nalivayko ◽  
O. Okushko ◽  
I. Bolbot ◽  
...  
Keyword(s):  
Single Phase ◽  
Modular Design ◽  
Short Circuit ◽  
Electrical Network ◽  
Electrical Networks ◽  
Circuit Breakers ◽  
New Energy ◽  
Short Circuits ◽  
Pole Scheme ◽  
Short Circuit Currents

According to PUE-2017, each group line must be protected against short circuits. Instant disconnection (cut-off) of the line in the event of short circuits provides an electromagnetic release of the circuit breaker. Reliable tripping is possible if the current of a single-phase short circuit is greater than the instantaneous tripping current. Today on the market are widely available circuit breakers with characteristics "B", "C" and "D", which are characterized by different multiplicities of the cut-off current of the electromagnetic release. Some European companies produce circuit breakers with other characteristics, which greatly expands the possibilities protection of electrical equipment. The difficulty in organizing the selectivity of protection is that the circuit breakers of modular design when switching off short circuits are characterized by the same switching time (not more than 0.05 s). The purpose of the research is to find ways to organize the selectivity of protection in electrical networks with voltage up to 1000 V using reliable values of short-circuit currents. In networks with a voltage of up to 1000 V, the current of a single-phase short circuit can be calculated fairly accurately if the exact values of all sections of the electrical network are known. In practice, it is not always possible to obtain reliable data on the numerical characteristics of the 0.4 kV network to which a new energy facility is connected. Therefore, it is proposed to consider part of the network as an active quadrupole, the characteristics of which are obtained by measurements at the point of connection. For further calculations it is necessary to know the voltage at the clamps of the four-pole scheme and the internal impedance. Based on the theory of four-pole scheme, you can get the original data for calculations without calculating the internal parameters of four-poles scheme. Thus, it is proposed to use a hybrid method for estimating the magnitude of probable short-circuit currents in electrical networks up to 1000 V when designing new energy facilities. Credible values of short-circuit currents will allow to organize selective protection of electric networks.

scholarly journals Features of presentation of certain elements in the elplek software product

2020 ◽  
pp. 34-44
Author(s):  
O. Gai ◽  
◽  
D. Husiatynskyi ◽  
Keyword(s):  
Power Systems ◽  
Theoretical Calculations ◽  
Short Circuit ◽  
Electrical Network ◽  
Software Products ◽  
Systems Software ◽  
Software Product ◽  
Complex Power ◽  
Calculation Results ◽  
Object Of Study

In order to simplify the modes analysis in power systems software tools for mathematical modeling of processes are used. There are many software products, but most of them are paid. For carrying out a laboratory work and obtain the results in certain sections of the thesis the authors of the article actively use the free software product "Elplek". But in a deeper study of the software product abilities we faced certain the task features of some parameters that are slightly differed from the generally accepted domestic methodology, which led to errors in the calculations in some versions of power schemes. The research aim is to study the peculiarities for setting the various elements parameters in the software product "Elplek" and to verify the adequacy of the existing models. At first the object of study was selected - a segment of the electrical network containing a small number of nodes - and a theoretical calculation of the short-circuit mode required parameters in this electrical network segment was carried out. Next an approach was proposed to set the elements parameters in the software product "Elplek" and based on this approach the simulation was carried out and as a result of which we obtained . Theoretical calculations showed that , i.e. the active part of the calculation results differ by 0.17 %, and reactive differ by 0.022%. This makes it possible to assert about the feasibility of using the proposed approach in the analysis of both normal and emergency modes of complex power supply schemes for consumers of certain power systems segments.

Ensuring Electrical Safety of a Mountain Quarry by Choosing Selective Relay Protection in the Electrical Networks with the Voltage above 1 kV

2021 ◽  
pp. 31-37
Author(s):  
R.V. Klyuev ◽  
◽  
V.I. Golik ◽  
I.I. Bosikov ◽  
O.A. Gavrina ◽  
...  
Keyword(s):  
Short Circuit ◽  
Relay Protection ◽  
Sensitivity Coefficient ◽  
Electrical Safety ◽  
Electrical Networks ◽  
Cable Network ◽  
Urgent Task ◽  
Short Circuits ◽  
Maximum Current Protection ◽  
Short Circuit Currents

An important and urgent task is the calculation and choice of selective relay protection, which allows to ensure safe conduct of work in the conditions of mountain quarries. In the work, on the example of mountain quarry, the calculations were carried out for ensuring electrical safety of the consumers in case of emergency modes occurrence due to the appearance of short-circuit currents. At the same time, short-circuit currents in a 6 kV network, maximum current protection and current cut-off were determined, a selectivity map of protection operation was drawn up. Calculations show that with the correct protection settings, the required sensitivity coefficient is ensured in case of the short circuits at any point in the network. The selectivity map of relay protection is drawn up for a normal scheme, in which sectional switches are off at all the voltage levels. The inclusion of these switches does not affect the choice of the protection operation current, and only increases the sensitivity coefficient of the current protection and earth-fault protection. When arranging power supply schemes for the consumers, it is recommended: not to connect more than two consumers of EKG-4.6 or PKTP-400/6 type to the feeder supplying EKG-8; do not connect more than four consumers of EKG-4.6 or PKTP-400/6 type to a separate feeder; 6 kV quarry network and the boiler should be powered from different busbar sections of KRU-2 complete switchgear; it is advisable to have a cable network length of at least 5–6 km from one section of 6 kV KRU-2 busbars, which will increase the reliability of protection against single-phase earth-faults.

scholarly journals Grid-connected Response Verification of AC Microgrid under Single Line-to-ground Short Circuit

2019 ◽  
pp. 1-10
Author(s):  
Maruf A. Aminu
Keyword(s):  
Power Systems ◽  
Reactive Power ◽  
Short Circuit ◽  
Synchronous Generator ◽  
Dynamic Responses ◽  
Single Line ◽  
Physical Systems ◽  
Short Circuits ◽  
Power System Performance ◽  
Grid Interconnection

In design of power systems, assumptions are made to model the physical systems. The assumptions may not sufficiently reflect the behavior of the system under normal and faulted conditions. Under short circuit conditions, system parameters vary significantly, particularly in microgrids with grid interconnection capabilities. This paper presents the result of validating the response of a microgrid which is capable of grid interconnection and islanding under voltage and reactive power control regimes. The microgrid is modeled to incorporate two wind turbines, each rated 5.5 kW, 400 V. The utility has synchronous generator rated 100 MW, 13.8 kV. Both the utility and microgrid are capable of exchanging active power and reactive power. Single line-to-ground short circuits are introduced and withdrawn at 30.00 s and 32.00 s, respectively. The dynamic responses of the testbed are captured pre-, during- and post-short circuit in grid-connected mode under both control regimes. The response of the testbed is verified to be consistent with established short circuit theory, verifying the validity of the system for short circuit detection and analysis. The testbed can therefore be used for short circuit and related studies, design optimization and power system performance prediction.

scholarly journals New Modeling of Steady-State Modes of Complex Electrical Grids of Power Systems

2018 ◽  
Vol 155 ◽  
pp. 01043 ◽  
Author(s):  
Arman Akhmetbayev ◽  
Dauren Akhmetbayev ◽  
Serik Zhumazhanov ◽  
Bauyrzhan Zhakishev
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Distribution Coefficients ◽  
Electrical Network ◽  
Electrical Networks ◽  
Topological Methods ◽  
Inverse Form ◽  
Electrical Grids ◽  
Complex Program ◽  
Theoretical Foundations

Classical methods for modeling the steady-state modes of complex electrical networks and systems are based on the application of nonlinear node equations. Nonlinear equations are solved by iterative methods, which are connected by known difficulties. To a certain extent, these difficulties can be weakened by applying topological methods. In this paper, we outline the theoretical foundations for the formation of the inverse form of nodal stress equations based on the topology of electrical networks and systems. A new topological method for calculating the distribution coefficients of node currents is proposed based on all possible trees of a directed graph of a complex electrical network. A complex program for calculating current distribution coefficients and forming steady-state parameters in the MATLAB environment has been developed.

Short circuits currents comparison of 6 (10) kV and 20 kV.

2020 ◽  
Vol 14 (1) ◽  
pp. 21-26
Author(s):  
S. SKRYPNYK ◽  
◽  
A. SHEINA ◽  
Keyword(s):  
Power System ◽  
Transmission Line ◽  
Transmission Lines ◽  
Power Supply ◽  
Short Circuit ◽  
Electric Arc ◽  
Electrical System ◽  
Three Phase ◽  
Short Circuits ◽  
Short Circuit Currents

Most failures in electrical installations are caused by short circuits (short circuits), which occur as a result of a failure in the electrical strength of the insulation of the conductive parts. A short circuit is an electrical connection of two points of an electric circuit with different values of potential, which is not provided by the design of the device, which interferes with its normal operation. Short circuits may result from a failure of the insulation of the current-carrying elements or the mechanical contact of the non- insulated elements. Also called a short circuit is a condition where the load resistance is less than the internal resistance of the power source. 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.

On the Problem of Selecting and Replacing Current Transformers for Relay Protection Devices

2020 ◽  
Vol 63 (6) ◽  
pp. 72-82
Author(s):  
Stanislav Kuzhekov ◽  
◽  
Andrey Degtyarev ◽  
Nikolay Doni ◽  
Aleksey Shurupov ◽  
...  
Keyword(s):  
Power Systems ◽  
High Speed ◽  
Short Circuit ◽  
Relay Protection ◽  
Electric Power Systems ◽  
Current Transformers ◽  
Magnetic Cores ◽  
Protection Devices ◽  
Short Circuits ◽  
The Stability

In connection with cases of incorrect operation of high-speed relay protection devices (RPD) in case of short circuits outside their range, the issue of replacing current transformers (CT) of class P with more ad-vanced current converters is relevant. The article shows that the decision to replace existing class P CTs with CTs with a non-magnetic gap should be made taking into account the probability of saturation of the magnetic cores of the latter in a transient short-circuit mode, as well as an increase in their dimensions compared to class P CTs. The issue of using optoelectronic current converters should be resolved after the latter are put into mass production, taking into account the difficulty of integrating the latter with the RPDs implemented using an Electromechanical base. In many cases, the correct functioning of high-speed RPDs without replacing existing CTs of class P can provide the following measures: the use of algorithms that increase the stability of the oper-ation of high-speed RPDs when the CT is saturated; taking into account in the calculations of the settings the rectangular characteristic of the CT magnetization in transient modes and the permissible deceleration of pro-tections under the condition of the dynamic stability of electric power systems; refusal to use CT connection groups (physical sum of currents, delta and star).

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