scholarly journals Study of the short-circuit currents in branches of distribution networks with trilateral power supply

2019 ◽  
Vol 618 ◽  
pp. 012020
Author(s):  
M I Matsankov
Keyword(s):  
Power Supply ◽  
Short Circuit ◽  
Distribution Networks ◽  
Short Circuit Currents

Influence of distributed power supply in distributed power distribution network

2021 ◽  
pp. 1-8
Author(s):  
Xin Shen ◽  
Hongchun Shu ◽  
Min Cao ◽  
Nan Pan ◽  
Junbin Qian
Keyword(s):  
Power Supply ◽  
Power Distribution ◽  
Short Circuit ◽  
Power Grid ◽  
Distribution Network ◽  
Distribution Networks ◽  
Power Supplies ◽  
Power Distribution Network ◽  
Power Sources ◽  
Distributed Power

In distribution networks with distributed power supplies, distributed power supplies can also be used as backup power sources to support the grid. If a distribution network contains multiple distributed power sources, the distribution network becomes a complex power grid with multiple power supplies. When a short-circuit fault occurs at a certain point on the power distribution network, the size, direction and duration of the short-circuit current are no longer single due to the existence of distributed power, and will vary with the location and capacity of the distributed power supply system. The change, in turn, affects the current in the grid, resulting in the generation and propagation of additional current. This power grid of power electronics will cause problems such as excessive standard mis-operation, abnormal heating of the converter and component burnout, and communication system failure. It is of great and practical significance to study the influence of distributed power in distributed power distribution networks.

scholarly journals Choosing the type of equivalent circuit of traction substation when calculating short-circuit currents in 25 kV power supply system

2020 ◽  
Vol 79 (3) ◽  
pp. 139-144
Author(s):  
E. P. Figurnov ◽  
Yu. I. Zharkov ◽  
N. A. Popova
Keyword(s):  
Equivalent Circuit ◽  
Power Supply ◽  
Power Supply System ◽  
Short Circuit ◽  
Supply System ◽  
The Other ◽  
Equivalent Circuits ◽  
Traction Substation ◽  
Traction Network ◽  
Short Circuit Currents

When calculating short circuit currents in the traction network, it is necessary to take into account the input resistance of the traction substation, including the resistance of the transformers of the substation and the resistance of the power supply system. The input resistance during short circuit is determined based on the equivalent circuit of the external power supply system, of which this traction substation is an integral part. Traditionally equivalent circuit of a three-phase system has the form of a star, in which the resulting resistances in each phase are connected in series with a source of phase electromotive force, and these sources have a common point. Another equivalent circuit in the form of a triangle is possible, in which on each side the resulting resistances are connected in series with the source of linear electromotive force. It is important to note that neither one nor the other type of equivalent circuit is determined by the connection scheme of the transformer windings of the traction substation. It is only necessary to take into account the absence of a circuit for zero sequence currents. All elements of the equivalent circuit, as is known, should be brought to uniform basic conditions. If the parameters of these elements are expressed in named units, then the basic values are the effective voltage values of the main stage and the rated power of the power transformer of the traction substation. If the components of one and the other equivalent circuits are reduced to one stage of the operating voltage, for example 27.5 kV, then for the same elements of the power supply system, the resistance values in the equivalent circuit in the form of a triangle are three times larger than in the equivalent circuit in the form of a star. In this case, the input resistances of the traction substation for the one and the other equivalent circuits are absolutely identical. Therefore, in the calculation of short circuit currents of the traction network, you can use any of these equivalent circuits of the power supply system and traction substation. Formulas for calculating the resistances of the elements of the power supply system and electrical installations, given in the standards, manuals and reference books, relate to the equivalent circuit of the short circuit in the form of a star. When using an equivalent circuit in the form of a triangle, these resistances must first be tripled, and then divided by three when calculating the short-circuit currents. The meaninglessness of such an operation is obvious. The equivalent circuit of the traction substation and the external power supply system in the form of a triangle when calculating short circuits in the traction network has no advantages compared to the traditional equivalent circuit in the form of a star. The information on the linear currents on the primary and secondary windings of the traction substation transformer during a short circuit in the traction network is given, which is necessary to select the settings of its relay protection kit.

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.

scholarly journals Effect of Distributed Photovoltaic Generation on Short-Circuit Currents and Fault Detection in Distribution Networks: A Practical Case Study

2021 ◽  
Vol 11 (1) ◽  
pp. 405
Author(s):  
Daniel Alcala-Gonzalez ◽  
Eva Maria García del Toro ◽  
María Isabel Más-López ◽  
Santiago Pindado
Keyword(s):  
Renewable Energy ◽  
Radial Distribution ◽  
Short Circuit ◽  
Renewable Energy Sources ◽  
Distribution Network ◽  
Distribution Networks ◽  
Energy Sources ◽  
Protection Devices ◽  
Short Circuits ◽  
Short Circuit Currents

The increase in the installation of renewable energy sources in electrical systems has changed the power distribution networks, and a new scenario regarding protection devices has arisen. Distributed generation (DG) might produce artificial delays regarding the performance of protection devices when acting as a result of short-circuits. In this study, the preliminary research results carried out to analyze the effect of renewable energy sources (photovoltaic, wind generation, etc.) on the protection devices of a power grid are described. In order to study this problem in a well-defined scenario, a quite simple distribution network (similar to the ones present in rural areas) was selected. The distribution network was divided into three protection zones so that each of them had DG. In the Institute of Electrical and Electronic Engineers (IEEE) system 13 bus test feeder, the short-circuits with different levels of penetration were performed from 1 MVA to 3 MVA (that represent 25%, 50%, and 75% of the total load in the network). In the simulations carried out, it was observed that the installation of DG in this distribution network produced significant changes in the short-circuit currents, and the inadequate performance of the protection devices and the delay in their operating times (with differences of up to 180% in relation to the case without DG). The latter, that is, the impacts of photovoltaic DG on the reactions of protection devices in a radial distribution network, is the most relevant outcome of this work. These are the first results obtained from a research collaboration framework established by staff from ETSI Civil and the IDR/UPM Institute, to analyze the effect of renewable energy sources (as DG) on the protection devices of a radial distribution network.

scholarly journals Improvement of protection of distribution of sectioned lines with distributed generation sources (DGS)

2020 ◽  
pp. 67-77
Author(s):  
A. Omelchuk ◽  
◽  
S. Voloshchyn ◽  
L. Martyniuk ◽  
Yu. Kaidenko ◽  
...  
Keyword(s):  
Distributed Generation ◽  
Short Circuit ◽  
Relay Protection ◽  
Short Circuit Current ◽  
Distribution Networks ◽  
Distance Protection ◽  
Operating Modes ◽  
Maximum Current ◽  
Current Cutoff ◽  
Short Circuit Currents

When powered from a backup source, the short-circuit currents in the protected area are much lower than the current cutoff insert installed at the sectioning point, therefore, in this case, the current cutoff is ineffective. In cases where the maximum current directional protection (MCDP) does not provide the required sensitivity, it is advisable to use distance protection with dependent exposure on sectioned lines and lines from distributed generation sources (DGS) in a significant decrease in voltage on the DGS buses during external short circuits through a relatively large reactance of small and medium power. Different modes of operation of sectioned lines from DGS are characterized by a change in the direction of flow of the load current and short-circuit current. Therefore, on such lines, maximum current directional protections can be applied, which provide selective action of adjacent sets of line protection in different modes of their operation. The use of definite time protection leads to the accumulation of a long time delay for the protection installed on the main switch (especially when several sectioning switches are installed on the line), which complicates the coordination of the protection of the main sections of the lines from the protection of the supply substations. The article deals with the problems of improving relay protection for distribution networks with distributed generation sources (DGS). Paying attention to the peculiarities of protection operation under different operating modes of such networks, namely: normal and post-emergency. The protection of lines from DGS must meet the general requirements for ensuring the necessary sensitivity, selectivity of action for different types of damage. Difficulties in ensuring the required sensitivity when using overcurrent protection and current cutoff in such networks are caused by the low level of short-circuit currents from backup sources. The features of the implementation of relay protection in sectioned networks when they are powered from the DGS are given. The expediency of using remote triggering devices for distance protection to increase the sensitivity of protection of sectioned lines from DGS has been substantiated.

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