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Ground Fault Location in Compensated Distribution Network
Topolánek, David ; Janíček,, František (referee) ; Mišák,, Stanislav (referee) ; Toman, Petr (advisor)
The most widespread system of an earthing neutral point of a supply transformer in a MV network is an earthing through an arc-suppression coil. In this case of a resonant-earthed power system a fault current is compensated by the suppression coil and only residual current flows through a fault point. A value of the residual current is much smaller then a value of an original capacitive current of the network and is not dependent on the fault location. According to that reasons it is really complicated to fast and accurately determine the fault point location. Since nowadays used methods for the ground fault location inside wide distribution networks have a lot of disadvantages, the thesis is focused on a proposal of a new method for the ground fault location especially inside of a compensated network. The main reasons for a consecutive installation of power quality meters into distribution transformer substations are a power quality monitoring and a global evolution of an electrical network onto the “SmartGrids”. In case that all results from the meters are properly synchronized and centralized, new possibilities of control or of an evaluation of a network are enabled. This doctoral thesis proposes the possibility for the ground fault detection with an aid of synchronized records recorded on the low-voltage side of the distribution transformers 22/0.4 kV into the network equipped with automatics for short-time increasing of an active part of a faulty current. The described method uses a voltage drop evoked by connecting of the auxiliary resistor for location of the faulty section. The proposed method is tested with help of numerical model which presents a part of the distribution network Series of simulation are executed and correct function and force function of the method is reviewed. Finally the thesis describes real experiment and also a confrontation between simulation and real measuring, and also possibilities of method usage are commented.
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Protection functions of the REX 640 terminal in case of earth faults
Siegel, Josef ; Bukvišová, Zuzana (referee) ; Wasserbauer, Vojtěch (advisor)
This bachelor thesis deals with the protection, implementation and evaluation of test for fault condition indicators. Thesis focus on earth fault indicators. These protections must be able to evaluate earth faults in compensated, compensated with auxiliary resistor, unearthed and high-resistance earthed networks. Furthermore, part of the thesis is research of methods of earth fault detection, including their principles and function description.
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Device for wireless transmission of electric current measurement data
Beran, Tomáš ; Čech, Ondřej (referee) ; Vyroubal, Petr (advisor)
The master thesis deals with the design of a communication and measurement subsystem for a device that processes current waveforms on medium voltage lines. The device consists of a source part, a measuring part with a current transformer, and a communication part. The work specifies the requirements for the communication and measurement part given by the customer. Based on these requirements, a communication protocol is selected and described that meets the requirements. Subsequently, the components forming the measurement subsystem are described. Furthermore, the circuit design of the selected components, including the design of the printed circuit boards is carried out. The PCB is then assembled and brought to life. The presented results are then measured on it.
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Protection functions of the REX 640 terminal in case of earth faults
Siegel, Josef ; Bukvišová, Zuzana (referee) ; Wasserbauer, Vojtěch (advisor)
This bachelor thesis deals with the protection, implementation and evaluation of test for fault condition indicators. Thesis focus on earth fault indicators. These protections must be able to evaluate earth faults in compensated, compensated with auxiliary resistor, unearthed and high-resistance earthed networks. Furthermore, part of the thesis is research of methods of earth fault detection, including their principles and function description.
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Development of the tool for application of the method for localization of unsymmetrical faults
Pospíšil, Tomáš ; Vyčítal, Václav (referee) ; Topolánek, David (advisor)
In resonant earthed distribution systems, the capacitive current of the system is compensated by grounding via a arc suppression coil. The level of fault current is then very small and independent on the fault location which greatly complicates the rapid finding of the fault site. At this moment there is no method to be used to directly locate the site of a single-phase fault in the distribution network, new methods and solutions are being constantly sought to address the shortcomings of the existent localization methods. The diploma thesis deals with the design of a universal software tool that allows to apply a new method of locating an asymmetric fault in the distribution network. The tool is created in a MATLAB environment and utilizes the negative sequence voltage measured on the low-voltage sides of the distribution transformers and the negative sequence current measured behind the power transformer. By using the proposed tool, it is possible to read the parameters of any part of the distribution system that the user enters together with the measured values of the voltage and current into the initialization file. After the specified network parameters are loaded, a numerical model is created, which is then used for the method. In the work is described in detail the way of entering the parameters of the network into the initialization file, the method of automatic assembling of the numerical model based on the entered data and the possibility of customizing the calculation parameters. At the end of the thesis, the functionality of the proposed software tool is verified on data from simulation of the test network.
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Testing of the admitance principle of the fault indicator
Musil, Milan ; Vyčítal, Václav (referee) ; Topolánek, David (advisor)
The thesis deals with the proposal, implementation and evaluation of test for fault condition indicators. Thesis focusing on earth fault indicators based on admittance principles. These indicators must be able to evaluate earth faults in compensated, compensated with auxiliary resistor, unearthed and high-resistance earthed networks. The proposed tests verify the current and voltage measurement errors in inputs including monitored characteristic variables such as conductance and susceptance. The proposed test are applied to a selected ample of the fault indicator. As part of the tests, the indicator is subjected to secondary test using the Omicron CMC256plus tester as well as test on fault records that have been converted to COMTRADE for this purpose. The last series of tests carried out uses the physical model of the medium voltage system, where the tested equipment is subjected to fault states in the compensated whit auxiliary resistor system and isolated system. Furthermore, part of the thesis is research of new methods of earth fault detection, including their principles and function description. Also included in the thesis is an overview of manufacturers of indicators, or protection, who are involved in the production of earth fault protection.
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The Indication of Earth Faults in Overhead Lines
Pospíšil, Zdeněk ; Topolánek, David (referee) ; Toman, Petr (advisor)
This master´s thesis deals with the indication and localization of earth faults in overhead lines. Earth fault is the most frequently occurring type of fault in medium voltage overhead lines – it covers approx. 95% of all faults and is very difficult to indicate and localize them correctly and in time with currently available methods on the market. Therefore is very important to study earth fault and its indication, localization. The thesis consists of a theoretical and a practical part. The theoretical part deals with faults in overhead networks with different type of neutral grounding, mainly with one phase to the ground fault in the compensated, ungrounded, solidly grounded and via resistance grounded networks. Most of the theoretical part is dedicated to one phase to the ground fault in the compensated and ungrounded networks, where this type fault is called the earth fault. In the compensated and ungrounded networks is described in details behavior – voltage and current relations during both steady state and transient state earth fault. The theoretical part is further dedicated to detection methods of earth faults and their preconditions for use. There is described also in details the complete procedure of earth fault detection, which includes indication, unhealthy feeder determination and exact position or line section localization. End of the theoretical part is then focused on determination of accuracy requirements for measurement of basic quantities and computation of other parameters. The practical part deals with a work at medium distribution network model, which includes familiarization with the model, detailed verification of its functionality and behavior during the earth fault, obtaining faults records and algorithmization of methods: method of qu – diagram and method of first half - period, which are able to detect unhealthy feeder. This part of the thesis was put together based on a demand of company Mega, corp., which wanted to verify function of both above mentioned and by them not yet tested methods.
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Short Circuit Calculation of MV Grid
Knápková, Dagmar ; Topolánek, David (referee) ; Toman, Petr (advisor)
This bachelor’s thesis deals with the faults in the distribution networks, focusing on shortcircuits as the most common and the most signiĄcant types of faults. The thesis is divided into theoretical and practical part. In the theoretical introduction, describes the types of faults in distribution networks with a focus on the short-circiuts, their causes, and the impact on distribution networks. Follows a description of the time course of short-circuit currents, short-circuit calculation simpliĄcation assumptions, the formula for calculating the impedance of the various elements of the short-circuits schema and the calculation methods of short-circuit currents in accordance with ČSN EN 60909-0. In the practical part, there is an example of the calculation of simple network conĄguration. Follows an analysis of the real network, including the analysis of the method of operation and the selection of appropriate method for the calculation of the short-circuit. After that are carried out practical calculations short-circuit conditions in four places on the network, and three diferent types of short circuits. For one-phase short-circuit is subsequently carried out the distribution of currents in a parallel branch of the distribution lines. At the conclusion of the bachelor’s thesis is caried out evaluation the results and analysis of the data obtained by calculation.
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Earth fault relay testing
Herůfek, Radek ; Topolánek, David (referee) ; Orságová, Jaroslava (advisor)
Bachelor thesis deals with an earth fault relay in compensated medium voltage distribution network. At the beginning of the thesis is described the method of operation compensated system and its advantages and disadvantages of using it. In addition, there is explained the definition of the ground fault, its types and there is outlined the method of solution asymmetrical single-phase fault. Thoroughly there is characterized distribution of voltages and currents, which is important for determination of affected and unaffected outlet. Among others, there is described the mode of action the arc suppression coil on caused fault current and also there are presented the auxiliary systems automation. In the next part the basic requirements for protections and its basic kinds are described. Finally the theoretical part describes principle of the earth fault relays and is presented means and methods used for indicate an affected outlet and earth fault localization. In the practical part, follows more detailed description of the protection REM 543 and testing equipment OMICRON CMC 256 +. In addition, there is explained connection process and setting selected functions and modules for testing earth fault relay. Assessment of generated and played transient disturbance records at the end.
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Simulation of Broken Conductor in Distribution Network by ATP-EMTP Program
Pacula, Václav ; Novotný, Jan (referee) ; Paar, Martin (advisor)
When broken conductor will impact on the ground. In isolated networks to ground fault occurs. For fault detection is the most commonly used method of zero-sequence voltage. The principle of the method is the sum of the voltage in all phases in the symmetric systém is the sum zero. The aim is to compare this method with the method of symmetrical sequence method and timeshiftomg. The method of symmetrical sequences compares sequency currents. To change the status of the systemis changed period, this method is based on the time shift.For comparison is used the ATP-EMTP program, that simulates the electrical transients. In this program are designed network model in which, these methods are investigated. It is a simple model of an idealized model and part of distribution network. After the simulation waveforms of events are processed and the results found faultdetection. Protection used today are based on measurements of zero-sequence voltage. A newer method of protection that extends further the possibility of detection and localization.
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