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.

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

scholarly journals Comparative Analysis of High-Voltage Power Line Models for Determining Short-Circuit Currents in Towers Earthing Systems

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4729
Author(s):  
Rafał Tarko ◽  
Jakub Gajdzica ◽  
Wiesław Nowak ◽  
Waldemar Szpyra
Keyword(s):  
High Voltage ◽  
Current Distribution ◽  
Single Phase ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Power Line ◽  
Power Lines ◽  
Distribution Analysis ◽  
Short Circuits ◽  
Short Circuit Currents

The article deals with the problems of single-phase short-circuit current distribution in overhead power lines. Short-circuit disturbances cause many negative phenomena in power networks. Since experimental studies of short-circuits in real networks are practically impossible to perform, these effects can be evaluated only theoretically, based on short-circuit current calculations with the use of appropriate mathematical models. Although short-circuit modeling is considered to be one of the simplest power system calculations, the exact mathematical description of the phenomena occurring at short-circuits is complex. Simplified normative methods are often used for short-circuit current calculations; however, this does not give ground for a thorough analysis of short-circuit current distribution in power lines. The distributions are analyzed using power line models with different degrees of complexity in line with the assumptions made for a given model. The paper presents the problem of current distribution analysis in high-voltage overhead lines for single-phase faults to the tower structures. Simulation studies were conducted on the models developed for the calculation of short-circuit currents in the high-voltage power line earthing. The objective of the analysis was to assess the validity of simplification assumptions followed by practical recommendations on the applicability of the models.

scholarly journals The influence of changing resistance on the determination accuracy of short circuits in power lines

2021 ◽  
Vol 288 ◽  
pp. 01091
Author(s):  
Serdar Nazarov ◽  
Gurbangulych Kelov ◽  
Berdimyrat Gochyev
Keyword(s):  
Single Phase ◽  
Short Circuit ◽  
Stable State ◽  
Short Circuit Current ◽  
Scientific Work ◽  
Electric Power System ◽  
Electrical Networks ◽  
Zero Sequence ◽  
Short Circuits ◽  
Maintenance Personnel

In high-voltage electrical networks, the occurrence of short circuits leads to forced interruptions in the power supply of large consumers and disruptions in intersystem communications. More than 65% of all types of occurring short circuits are single-phase short circuits [1]. In a single-phase short circuits (SPSC), a change in the zero sequence resistance (ZSR) especially significantly affects the inaccuracy in detection of damage sites (DDS). When choosing DDS methods, preference is given to remote methods according to the parameters of the emergency conditions (PEC), which are recorded by special instruments or determined from the oscillograms of emergency conditions. The use of modern microprocessor-based relay protection and automation devices (RPA) [26] or emergency event recorders allow viewing the oscillograms of emergency events. In a branched 110 kV network with a complex configuration, the DDS accuracy is influenced by a change in the ZSR. Averaging of specific parameters often leads to erroneous results. The choice of one value from the oscillograms puts the maintenance personnel in difficulty. In the scientific work, the influence of changes in the ZSR on the accuracy of the DDS is considered. The changes in the ZSR are influenced by the position of the on-load voltage regulator (OLTC) switches of transformers with a grounded neutral. In the work, for a more accurate record of the specific parameters of the network, a calculation program has been compiled, which allows making changes in the calculated specific parameters of the network. To determine the short-circuit current from the oscillograms, it is proposed to determine the stable state of accidents in which the current value will be approximately the same. The analysis of the oscillograms of SPSC in 110-220 kV networks in the southern part of the electric power system of Turkmenistan has been carried out.

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 Post-Arc Characteristics of High-Current Arcs in Vacuum Circuit-Breakers

2019 ◽  
Vol 6 (2) ◽  
pp. 170-174
Author(s):  
N. Wenzel ◽  
W. Haas
Keyword(s):  
Short Circuit ◽  
Early Period ◽  
Metal Vapor ◽  
Transverse Magnetic ◽  
High Current ◽  
Electric Resistance ◽  
Circuit Breakers ◽  
Arc Characteristics ◽  
Current Zero ◽  
Short Circuit Currents

The post-arc (PA) characteristics of vacuum arcs in transverse magnetic field contacts are studied for short-circuit currents of up to 123 kA peak and transient recovery voltages below 875 V. The measured PA currents are interpreted in terms of an Electric Resistance Model and the models of Andrews-Varey, Langmuir-Child, and Slepian-Schmelzle. Whereas in the late PA period, the calculations do not agree well with the measurements, the PA behavior is well described in the early period after current-zero. It is concluded that the PA discharge is amplified by ionization of metal vapor particles in the boundary sheath due to electron impact.

scholarly journals Development of a Method and Algorithm for Inhibiting an Automatic Transfer Switch of the Circuit Breaker for a Sustained Short-Circuit

2020 ◽  
Vol 220 ◽  
pp. 01011
Author(s):  
Igor Nikolaevich Fomin ◽  
Roman Pavlovich Belikov ◽  
Tatyana Anatolyevna Kudinova ◽  
Nailya Kamilevna Miftakhova
Keyword(s):  
Short Circuit ◽  
Circuit Breaker ◽  
Electrical Equipment ◽  
Ring Network ◽  
Circuit Breakers ◽  
Emergency Situations ◽  
Short Circuit Currents

Circuit breakers with automatic transfer switches (ATS) are designed in such a way that when the voltage disappears during a short-circuit (SC) in the ring network line, the ATS device is triggered. At the same time, its switch is turned on at short-circuit, then it is turned off with acceleration. Even a shortterm switching on of the automatic transfer switch for a sustained short-circuit leads to emergency situations [1,2]. The electrical equipment of the ring network spare line is exposed to high emergency short-circuit currents, and the consumers powered by the spare transformer are turned off. It is possible to minimize and eliminate the damages caused by the above mentioned cases by inhibiting the switching on of the circuitbreaker of the automatic transfer switch.

scholarly journals Arcing Behaviors in the Large-capacity HV SF6 Gas-blast Interrupters

2019 ◽  
Vol 6 (2) ◽  
pp. 140-143 ◽  
Author(s):  
S. A. Averyanova ◽  
E. Tonkonogov
Keyword(s):  
High Voltage ◽  
Short Circuit ◽  
Dielectric Strength ◽  
Numerical Results ◽  
Circuit Breakers ◽  
Large Capacity ◽  
Recovery Processes ◽  
Strength Recovery ◽  
Turbulence Effects ◽  
Short Circuit Currents

A comprehension of the dielectric strength recovery processes during the interruption of short-circuit currents in the high-voltage SF<sub>6</sub> gas-blast circuit breakers is necessary for their modernisation in order to increase the rated voltage and short circuit breaking current per one break. This paper presents numerical results of the turbulence effects on the interruption ability in the SF<sub>6</sub> extinguishing arc chamber.

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