scholarly journals Researching the Blocking of Current Protection of Electrical Power Units with Transformers

2020 ◽  
Vol 63 (6) ◽  
pp. 491-499
Author(s):  
F. A. Romaniuk ◽  
V. Yu. Rumiantsev ◽  
Yu. V. Rumiantsev ◽  
A. A. Dziaruhina ◽  
P. I. Klimkovich
Keyword(s):  
Short Circuit ◽  
Electrical Power ◽  
Degree Of Saturation ◽  
Phase System ◽  
Asymmetric Mode ◽  
Negative Sequence ◽  
Three Phase ◽  
Short Circuits ◽  
Magnetizing Current ◽  
Higher Sensitivity

The magnetizing current inrush appears in electrical power units equipped with transformers in case of no-load energizing of the power transformers and in a number of other cases. This phenomenon could cause a false triggering of the current protection. To prevent incorrect actions of the current protection during the magnetizing current inrush a protection blocking is carrying out. The blocking principle operation is based on the fact that in a three-phase system in normal mode and in case of symmetrical short circuit the first harmonics contained in the phase currents of electrical installations form a direct sequence and the second ones – the negative sequences. In case of an asymmetric mode, including an asymmetric short circuit, the negative sequence appears, formed by the first harmonics that are part of the phase currents of the specified system. In magnetizing current inrush modes, second harmonics of significant magnitude are present in phase currents, which form the negative sequence. Based on the analysis of the information parameters of the specified sequences currents, identification of the magnetizing current inrush and short-circuit modes is performed with the implementation of the protection blocking if necessary. The study of the current protection blocking functioning was performed using computational experiment by analyzing the calculated changes of blocking parameter compared with the threshold setpoint. The specified researching is done by using the digital model that is implemented in the dynamic modeling environment MatLab-Simulink. As a result of the performed calculations, the principal operability of the proposed current protection blocking was confirmed that provides a fairly reliable identification of the magnetizing current inrush and short-circuits modes, regardless of the degree of saturation of current transformers. It was found that the proposed principle of the current protection blocking has a higher sensitivity in comparison with the classical one based on the estimation of the ratio of the second and first harmonics of the phase currents. In short-circuit modes in an electrical power units the proposed blocking causes a current protection operation delay that can be reduced by digital filters performance improvement. 

ENGINEERING ANALYSIS OF THE THREE-PHASE SHORT CIRCUIT MODE IN THE 10 KV ELECTRIC NETWORK TAKING INTO ACCOUNT THE INFLUENCE OF LOAD CURRENTS

2021 ◽  
pp. 74-83
Author(s):  
YURI D. VOLCHKOV ◽  
Keyword(s):  
Remote Monitoring ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Load Current ◽  
Electric Network ◽  
Operating Modes ◽  
Three Phase ◽  
Feed Network ◽  
Short Circuits ◽  
Switching Devices

Abstract. The load current aff ects the value of the short-circuit current in the electric network and, consequently, the voltage value. In some cases, this infl uence must be taken into account for the correct choice of switching devices, remote monitoring the operating modes of electric networks, and determining the modes. It is possible to disconnect loads connected through magnetic starters and contactors. Failure to consider the infl uence of the load current can lead to an incorrect interpretation of the identifi ed grid operating modes during remote monitoring and, as a result, incorrect dispatcher’s decisions. In addition, it is also insuffi cient to specify the choice of switching devices in the 10 kV feed network. The article describes a method for analyzing the three-phase short circuit mode in a 10 kV feed network, taking into account the infl uence of load currents. The method is exemplifi ed by the case of an actual electric network – the 10 kV ring feed network containing reclosers and receiving power from diff erent sections of lowvoltage buses of the “Kulikovskaya” 110/35/10 kV substation, belonging to the Branch of PJSC «DGC of Center”-“Orelenergo.” For this network, the values of the three-phase short-circuit currents at points with diff erent distances from the substation buses have been determined. The authors have fi guredout the values of the load currents and their shares in the total short-circuit current. The voltage values at different points of the network in the case of short circuits have also been determined. The research proves that the effect of the load current on the total short-circuit current should be taken into account for the case of remote short circuits.

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.

The Economic Operation of Common Coupling Groups of Distribution Transformer

2014 ◽  
Vol 521 ◽  
pp. 288-291
Author(s):  
Yu Sheng Quan ◽  
Xin Zhao ◽  
Hua Gui Chen ◽  
En Ze Zhou
Keyword(s):  
Single Phase ◽  
Short Circuit ◽  
Phase System ◽  
Distribution Transformer ◽  
Three Phase ◽  
Unbalanced Load ◽  
Transformer Coupling ◽  
The Difference ◽  
Short Circuit Fault ◽  
Better Than

Based on the method of symmetrical components of D, 11 and Y, o distribution transformer coupling two different effects of different magnetic circuit coupled to the three-phase system with a system-generated analysis and comparison. Analysis of the difference between the two groups of different connections on the transformer structure. Described in the single-phase short circuit fault clearing, 3n harmonic current suppression and affordability aspects of single-phase unbalanced load, D, ll coupling transformers are significantly better than Y,0 coupling transformer. This has necessarily important for the study of energy loss reduction.

Application of Probabilistic Neural Networks in Fault Diagnosis of Three-Phase Induction Motors

2013 ◽  
Vol 433-435 ◽  
pp. 705-708 ◽  
Author(s):  
Shuo Ding ◽  
Xiao Heng Chang ◽  
Qing Hui Wu
Keyword(s):  
Neural Network ◽  
Fault Diagnosis ◽  
Induction Motors ◽  
Probabilistic Neural Network ◽  
Short Circuit ◽  
Model And Simulation ◽  
Fast Training ◽  
Three Phase ◽  
Short Circuits ◽  
Stator Fault

In fault diagnosis of three-phase induction motors, traditional methods usually fail because of the complex system of three-phase induction motors. Short circuit is a very common stator fault in all the faults of three-phase induction motors. Probabilistic neural network is a kind of artificial neural network which is widely used due to its fast training and simple structure. In this paper, the diagnosis method based on probabilistic neural network is proposed to deal with stator short circuits. First, the principle and structure of probabilistic neural network is studied in this paper. Second, the method of fault setting and fault feature extraction of three-phase induction motors is proposed on the basis of the fault diagnosis of stator short circuits. Then the establishment of the diagnosis model based on probabilistic neural network is illustrated with details. At last, training and simulation tests are done for the model. And simulation results show that this method is very practical with its high accuracy and fast speed.

scholarly journals ANALYSIS OF OVERVOLTAGE POSSIBILITY ON THE EXCITATION WINDING OF A SYNCHRONOUS GENERATOR OF AUTONOMOUS POWER SUPPLY SYSTEM IN CASE OF EXTERNAL SYMMETRICAL SHORT CIRCUIT

2021 ◽  
pp. 112-115
Author(s):  
V.B. Beliy ◽  
Keyword(s):  
Power Systems ◽  
Power Supply ◽  
Short Circuit ◽  
Electric Energy ◽  
Synchronous Generator ◽  
Synchronous Generators ◽  
Excitation System ◽  
Three Phase ◽  
Short Circuits ◽  
Analytical Expressions

Reliable supply of consumers with electric energy largely depends on the reliability of power source function-ing. In the context of this paper it depends on synchronous generators operating in autonomous power supply sys-tems. In contrast to the power plant generators which are part of power systems and are protected from the loads by sufficiently large resistances, power supply systems withautonomous generators are characterized by rather low resistances. Abrupt changes in the supply load parameters, their own transient and emergency modes, for example, short circuits at the generator terminals, forcing excitation, etc. may lead to various failures in the synchronous gener-ator operation. This paper discusses the possibility of over-voltage in the valve excitation system of a synchronous generator with external three-phase short circuits. On the basis of analytical expressions describing the physical pro-cesses occurring in the excitation system of synchronous generators, the conditions for the occurrence of overvolt-ages are identified

scholarly journals Improvements on the Carrier-Based Control Method for a Three-Level T-Type, Quasi-Impedance-Source Inverter

Electronics ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 677 ◽  
Author(s):  
Fermín Barrero-González ◽  
Carlos Roncero-Clemente ◽  
María Isabel Milanés-Montero ◽  
Eva González-Romera ◽  
Enrique Romero-Cadaval ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Pulse Width Modulation ◽  
Control Method ◽  
Short Circuit ◽  
Harmonic Distortion ◽  
Line Voltage ◽  
Photovoltaic Array ◽  
Blocking Voltage ◽  
Three Phase ◽  
Short Circuits

The boost feature that characterizes Z-source and quasi-Z-source converters is usually achieved by means of a proper insertion of short-circuit states in the full DC-link. In this work, a novel pulse width modulation carrier-based strategy for a three-phase, three-level T-type, quasi-Z-source inverter is introduced, based on the addition of alternate short-circuits in the two halves of the DC-link bus. This technique achieves better performance, less electromagnetic interference, and lower harmonic distortion of the output line-to-line voltage compared to the traditional methods based on the full DC-link shoot-through. At the same time, generating the switching states is to easy implement. The proposed strategy permits the use of electronic devices with lower blocking voltage capability, thus improving converter reliability, size, and cost. The new method may be implemented in another multilevel inverter with an impedance-source network as well. A comprehensive simulation study is performed in order to validate the adopted method, with different inverter input voltages, which is taken as representative of a photovoltaic array. Comparisons are conducted with conventional strategy insertions using the same topology in order to show the improvements achieved.

scholarly journals Energy efficiency digital filter design for spectral analysis of primary electrical values

2019 ◽  
Vol 104 ◽  
pp. 02002
Author(s):  
Vladimir Mladenovic ◽  
Caslav Stefanovic ◽  
Sergey Makov
Keyword(s):  
Digital Filter ◽  
Filter Design ◽  
Point Of View ◽  
Electrical Networks ◽  
Analog Filter ◽  
Bilinear Transformation ◽  
Negative Sequence ◽  
Knowledge Based ◽  
Three Phase ◽  
Short Circuits

In this paper, the knowledge based design of digital filter for analysis of spectral components is illustrated. The primary electrical values are analyzed observing of the faults which appear by earth short circuits. The main point of view is negative sequence component and higher harmonics in distributed electrical networks. Method of symbolic processing is used to design digital filter that realizes negative sequence component. Designing of digital filter is based on active analog filter in the three-phase electrical networks using bilinear transformation. We use methods of computer algebra tools (Mathematica) to simulate processes in network. Also, we automatically derive properties of digital filter, and the knowledge embedded in symbolic expressions was used to simulate an example system. The characteristics of digital filter are given and annotated using different sampling frequency and entire cases of earth short circuits.

scholarly journals Induction Motor Stator Interturn Short Circuit Fault Detection in Accordance with Line Current Sequence Components Using Artificial Neural Network

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Gayatridevi Rajamany ◽  
Sekar Srinivasan ◽  
Krishnan Rajamany ◽  
Ramesh K. Natarajan
Keyword(s):  
Neural Network ◽  
Fault Detection ◽  
Induction Motor ◽  
Short Circuit ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Three Phase ◽  
Sequence Components ◽  
Negative Sequence Current ◽  
Short Circuit Fault

The intention of fault detection is to detect the fault at the beginning stage and shut off the machine immediately to avoid motor failure due to the large fault current. In this work, an online fault diagnosis of stator interturn fault of a three-phase induction motor based on the concept of symmetrical components is presented. A mathematical model of an induction motor with turn fault is developed to interpret machine performance under fault. A Simulink model of a three-phase induction motor with stator interturn fault is created for extraction of sequence components of current and voltage. The negative sequence current can provide a decisive and rapid monitoring technique to detect stator interturn short circuit fault of the induction motor. The per unit change in negative sequence current with positive sequence current is the main fault indicator which is imported to neural network architecture. The output of the feedforward backpropagation neural network classifies the short circuit fault level of stator winding.

Protection Study in the EPS, Electrical Power System

2021 ◽  
pp. 377-394
Author(s):  
Gustavo Vinicius Duarte Barbosa ◽  
José Ronaldo Tavares Santos
Keyword(s):  
Power Systems ◽  
Power System ◽  
Regulatory Agency ◽  
Short Circuit ◽  
Salt Spray ◽  
Electrical Power ◽  
Electrical Power System ◽  
Electrical Power Systems ◽  
Two Phase ◽  
Three Phase

Electrical power systems are susceptible to faults caused, for example, by storm, pollution, vandalism, lightning, salt spray, etc. The unscheduled interruption in the supply of electricity to consumers, whether industrial, residential, or commercial, entails severe fines for the transmission utility and/or electricity distributor, imposed by the regulatory agency. Thus, the EPS must have a well-dimensioned protection system, capable of identifying the fault, which is characterized by a single-phase, two-phase, three-phase short circuit, among others, and interrupt the missing section in the minimum time so that the effects of this lack are as small as possible for the SEP, especially with regard to its integrity and operational security.

A Study on DG Control Strategy and Grid Protection

2014 ◽  
Vol 521 ◽  
pp. 204-212
Author(s):  
Xin Chao Wang ◽  
Chen Xin Yang
Keyword(s):  
Load Capacity ◽  
Short Circuit ◽  
Current Source ◽  
Islanding Detection ◽  
Test Results ◽  
Total Load ◽  
Line Voltage ◽  
Negative Sequence ◽  
Three Phase ◽  
Negative Sequence Current

DG integration reduces the selectivity and sensitivity of grid relay protection. A new control algorithm is proposed. It shows that the negative sequence current will not be affected by DG when the DG is designed as a symmetric three-phase current source. In this case, the negative sequence characteristic can be utilized for grid protection during short-circuit faults. If DGs maximum power capacity is restricted to be lower than total load capacity, DG terminal line-voltage and the negative sequence voltage can be used as the criteria for islanding detection. Then it is possible to cutoff DG in order to fulfill the reclosing requirement. A complicated simulation system is designed using PSCAD/EMTDC program. Different short-circuit faults are simulated to verify the proposals. The test results confirm well with the conclusions.

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