Two-Phase Short Circuit in the Power Grid Powered by a Transformer with a Y/Δ-11 Winding Connection

2020 ◽  
pp. 25-30
Author(s):  
Aleksandr S. Serebryakov ◽  
Vladimir L. Osokin ◽  
Sergey A. Kapustkin
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Relay Protection ◽  
Electric Circuit ◽  
Operational Reliability ◽  
Research Purpose ◽  
Industrial Complex ◽  
Two Phase ◽  
Short Circuit Currents ◽  
Secondary Winding

The article describes main provisions and relations for calculating short-circuit currents and phase currents in a three-phase traction transformer with a star-triangle-11 connection of windings, which feeds two single-phase loads in AC traction networks with a nominal voltage of 25 kilovolts. These transformers provide power to the enterprises of the agro-industrial complex located along the railway line. (Research purpose) The research purpose is in substantiating theoretical equations for digital intelligent relay protection in two-phase short circuits. (Materials and methods) It was found that since the sum of instantaneous currents in each phase is zero, each phase of the transformer works independently. We found that this significantly simplifies the task of analyzing processes with a two-phase short circuit. In this case, the problem of calculating short-circuit currents in the traction network can be simplified by reducing it to the calculation of an ordinary electric circuit with three unknown currents. (Results and discussion) The article describes equations for calculating short-circuit resistances for one phase of the transformer when connecting the secondary winding as a star or a triangle. The currents in the phases of the transformer winding at short circuit for the star-triangle-11 and star-star-with-ground schemes are compared. It was found that when calculating short-circuit currents, there is no need to convert the secondary winding of the traction transformer from a triangle to a star. (Conclusions) It was found that the results of the research can be used in the transition of relay protection systems from electromagnetic relays to modern high-speed digital devices, which will increase the operational reliability of power supply systems for traction and non-traction power consumers.

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).

scholarly journals A modified prefix operator well suited for area-efficient brick-based adder implementations

2011 ◽  
Vol 9 ◽  
pp. 289-295
Author(s):  
I. Rust ◽  
T. G. Noll
Keyword(s):  
Integrated Circuits ◽  
High Speed ◽  
Short Circuit ◽  
Cmos Technology ◽  
Deep Submicron ◽  
Classical Operator ◽  
Signal Combination ◽  
Short Circuit Currents ◽  
Prefix Adders ◽  
Sub Wavelength

Abstract. The implementation of integrated circuits becomes more and more difficult in the Ultra-Deep-Submicron regime due to sub-wavelength lithography issues. An approach called Brick-Based Design was recently proposed to eliminate the disadvantages of staying with the classical approach to layout design. Prefix adders are a core component in a wide variety of applications due to their high speed and regular topology. In this paper, a modified prefix operator for prefix adders is proposed which is well suited for brick-style layout implementation and, in addition, offers an increase in efficiency. The proposed operator makes it possible to use a mirror gate for the generation of both generate and propagate signals, which exhibits a forbidden input signal combination. This "forbidden state" causes an increase in power dissipation due to transient short circuit currents. The effect of the forbidden state was quantified as part of a comparison against the classical prefix operator, based on 64-bit Sklansky adders implemented in a 40-nm CMOS technology. The effects of the forbidden state were found to be well acceptable. The implementation of the adder based on the proposed prefix operator reduces the area by 29% while increasing the power by 13% compared to one based on the classical operator.

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.

Solution of Topical Issues in Theory of Transformers

2021 ◽  
Vol 64 (3) ◽  
pp. 5-11
Author(s):  
Sergey Plotnikov ◽  
◽  
Оleg Kolmakov ◽  
Keyword(s):  
Skin Effect ◽  
Magnetic Circuit ◽  
Short Circuit ◽  
Heating Time ◽  
Controversial Issues ◽  
Correction Factors ◽  
Parallel Operation ◽  
Thermal Tests ◽  
Short Circuit Currents ◽  
Secondary Winding

In the article, the authors summarized their experience in solving some controversial issues in the theory of transformers, and briefly outlined the essence of their developments. For power transformers of the TM series, the presence of an excess of the active resistance of the primary winding relative to the reduced active re-sistance of the secondary winding was established. The obtained correction factors, taking into account the electrical skin effect in the windings and their heating, can be used to calculate short-circuit currents and heat distribution in other types of transformers. An expression is given that makes it possible to correct the transfor-mation ratio of one of the transformers connected to parallel operation in such a way that it becomes possible to fully load both devices, despite their different short-circuit voltages. Expressions are presented that make it possible to reveal the ratio of hysteresis and eddy-current losses in the magnetic circuit of a particular trans-former, as well as the exponent with which the losses in the magnetic circuit depend on the frequency of mag-netization reversal. A method is proposed for determining the three components of losses in a magnetic circuit, based on an idle experiment at three frequencies. A method is described for determining the thickness of sheets of a magnetic circuit, at which the total losses in it are minimal, and a method for determining the heating time constant of dry transformers is presented, which makes it possible to accelerate their thermal tests.

scholarly journals Analisis Pengaruh Kompensasi Impedansi Urutan Nol (Kzn) terhadap Kehandalan Sistem Proteksi Rele Jarak (Distance Relay) pada Penghantar Harapan Indah di Gardu Induk Plumpang

2021 ◽  
Vol 4 (1) ◽  
pp. 1
Author(s):  
Deni Almanda ◽  
Juniyanto Juniyanto
Keyword(s):  
Single Phase ◽  
Short Circuit ◽  
Relay Protection ◽  
Protection System ◽  
Distance Relay ◽  
Two Phase ◽  
Test Tool ◽  
Three Phase ◽  
Zero Sequence ◽  
Short Circuit Fault

Pada saat terjadi gangguan hubung singkat di saluran transmisi Gardu Induk Plumpang, rele jarak berfungsi sebagai proteksi utama. Penelitian ini bertujuan untuk mengetahui pengaruh kompensasi impedansi urutan nol (kzn) terhadap kehandalan sistem proteksi rele jarak (distance relay) pada penghantar harapan indah di Gardu Induk Plumpang. Setting rele jarak yang didapatkan dari PT PLN (Persero) UPT Pulogadung disimulasikan menggunakan alat uji Omicron. Hasil simulasi gangguan hubung singkat satu fasa, gangguan hubung singkat dua fasa, dan gangguan hubung singkat tiga fasa menggunakan setting lama Z1 = 2.58 Ω, Z2 = 3.87 Ω, dan Z3 = 7.30 Ω, kZn = 0.93 Ω < -0.4° rele jarak tidak bekerja selektif, maka dilakukan resetting. Hasil resetting rele jarak yaitu Z1 = 2.58 Ω, Z2 = 3.87 Ω, dan Z3 = 7.30 Ω, kZn = 0.68 Ω < -0.6°. Setelah dilakukan resetting dan disimulasikan gangguan hubung singkat satu fasa, gangguan hubung singkat dua fasa, dan gangguan hubung singkat tiga fasa, rele jarak bekerja secara handal. Kesimpulannya kZn dapat mempengaruhi kehandalan sistem proteksi rele jarak pada penghantar harapan indah di Gardu Induk Plumpang.In the event of a short circuit in the transmission line of the Plumpang Substation, the distance relay serves as the main protection. This study aims to determine the effect of zero sequence impedance compensation (kzn) on the reliability of the distance relay protection system at the Harapan Indah conductor at the Plumpang Substation. The distance relay setting obtained from PT PLN (Persero) UPT Pulogadung was simulated using the Omicron test tool. Simulation results of single phase short circuit, two phase short circuit, and three phase short circuit using the old setting Z1 = 2.58 Ω, Z2 = 3.87 Ω, and Z3 = 7.30 Ω, kZn = 0.93 < -0.4° relay distance does not works selectively, then resetting is done. The results of resetting the distance relay are Z1 = 2.58 Ω, Z2 = 3.87 Ω, and Z3 = 7.30 Ω, kZn = 0.68 < -0.6°. After resetting and simulating single-phase short circuit, two phase short circuit, and three phase short circuit fault, the distance relay works reliably. In conclusion, kZn can affect the reliability of the distance relay protection system on the beautiful hope conductor at the Plumpang Substation.

scholarly journals Calculation of two-phase ground fault current with consideration of equipment grounding specifications

2018 ◽  
Vol 19 (12) ◽  
pp. 468-473
Author(s):  
Aleksiej Kosjakow ◽  
Aleksandr Suhoguzow
Keyword(s):  
High Voltage ◽  
Short Circuit ◽  
Metal Resistance ◽  
Fault Current ◽  
Electrical Networks ◽  
Two Phase ◽  
Grounding Resistance ◽  
Ground Fault ◽  
Isolated Neutral ◽  
Short Circuit Currents

The article describes ways of calculating two-phase ground fault current in electrical networks with isolated neutral for needs of calculating thermal resistance in equipment's grounding elements. Grounding resistance and metal resistance of high-voltage equipment are added to the existing methods of short circuit currents calculation.

scholarly journals Improving the efficiency of relay protection at a mining and processing plant

2021 ◽  
Vol 248 ◽  
pp. 300-311
Author(s):  
Roman Klyuev ◽  
Igor Bosikov ◽  
Oksana Gavrina
Keyword(s):  
Power Supply ◽  
Short Circuit ◽  
Relay Protection ◽  
Normal Operation ◽  
Processing Plant ◽  
Overcurrent Protection ◽  
Short Circuits ◽  
Analysis Of Failures ◽  
Efficiency And Reliability ◽  
Short Circuit Currents

The paper presents the results of constructing effective relay protection in the power supply system of a mining and processing plant (MPP). A brief description of the MPP is given, the power supply and substitution circuits used to calculate the short-circuit currents are given. A statistical analysis of failures in the electric network of the MPP has been carried out, which makes it possible to draw conclusions about the nature of failures ranges. Analysis of the registered faults shows that a significant part of them are line-to-earth faults, which in most cases turn into multiphase short circuits, which are interrupted by overcurrent protection. In order to improve the efficiency and reliability of the relay protection, the power supply scheme of the MPP was refined and analyzed. The calculation of the short-circuit currents was made, which made it possible to calculate the settings of the relay protection and give recommendations on the place of its installation and adjustment in order to ensure the normal operation of electricity consumers. To reduce the number of failures to the cable insert on the line leaving the administrative and household complex (AHC), and to increase the reliability of power supply to consumers, it is advisable to divide the capacities of the existing 10 kV line into two parallel ones by laying a second line. It is recommended to install a current cut-off on the line outgoing to the AHC, the feasibility of the installation of which was shown by calculations. This will reduce the chance of failures to the cable gland. Data on the setting currents of overcurrent protection and current cut-off are given on the selectivity card.    

Some aspects of the calculation of short circuits in mine distribution networks. The calculation of the effective values of the short-circuit currents is carried out in order to determine the minimum

2020 ◽  
Vol 14 (1) ◽  
pp. 66-69
Author(s):  
V. KALINICHENKO ◽  
◽  
I. PRIDATKO ◽  
Keyword(s):  
Short Circuit ◽  
Distribution Networks ◽  
Two Phase ◽  
Cable Network ◽  
Transformer Substation ◽  
Three Phase ◽  
Short Circuits ◽  
Artificial Introduction ◽  
Short Circuit Currents ◽  
Circuit Power

The calculation of the effective values of the short-circuit currents is carried out in order to determine the minimum value of the current of the two- phase short-circuit required to select the settings of the means of protection, as well as the maximum value of the current of the three-phase short-circuit required to test the switching equipment for the ability to switch off. In most studies, the calculation of short-circuit currents is carried out only taking into account the total resistance of the transformer substation and the cable network. They also take into account the maximum short-circuit power (100MVA) due to the use of high-voltage explosion-proof switchgear type KRUV-6 without taking into account the influence of the external network. An external network, in turn, may limit the short-circuit power below 100MVA. The calculation of the short-circuit power of the external system with regard to the network parameters was considered. The actual magnitude of this capacity differs from that accepted in the known calculations and is below these values due to the natural or artificial introduction of reactor reactance and causes an error of 10-40%. Remote short-circuits of the distribution network reduce the short-circuit power of the input terminals of the step-down transformers, and therefore the influence of the external network on the short-circuit currents in the district networks increases. This approach will allow the determination of short-circuit currents in the mine distribution networks with higher accuracy. This will reduce the risk of accidents in an explosive mining environment.

scholarly journals Experimental study of the operating modes of the resonant current-limiting device

2020 ◽  
Vol 220 ◽  
pp. 01049
Author(s):  
Dmitry V. Mikheev ◽  
Yelena N. Ryzhkova ◽  
Alex V. Udaratin ◽  
Regina Salikhova
Keyword(s):  
Short Circuit ◽  
Electric Circuit ◽  
Electrical Networks ◽  
Technical Object ◽  
Passive Element ◽  
Operating Modes ◽  
Current Limiting ◽  
Automation Equipment ◽  
Technical And Economic Indicators ◽  
Short Circuit Currents

Decreasing of short-circuit currents in power supply systems enables the usage of less expensive switching-protective devices with a lower breaking capacity and reduction of damage from the consequences of emergency events. In electrical networks of low, medium and high voltage classes, resonant current-limiting devices are used to solve this problem, along with other technical solutions. However, these devices have unsatisfactory weight and dimensions, high cost and other disadvantages. The technical and economic indicators of such devices can be improved through the use of a coil-capacitor (coilcap). Coilcap is a passive element of an electric circuit, which simultaneously possesses inductivecapacitive properties and performs the functions of a reactor and a capacitor in a single technical object. This paper presents a functional diagram of the implementation, design, operating principle and mathematical description of a resonant current-limiting device based on a coilcap. Physical modeling of the steady-state modes of the device (normal mode and current limiting mode) was carried out, and the possibility of limiting short-circuit currents due to the use of a coilcap was confirmed. The practical application of a resonant current-limiting device based on a coilcap can be effectively combined with switching-protective and current-limiting disconnecting devices, relay protection, and automation equipment.

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