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Verification of the Vdip method on the physical model of the MV network
Krčál, Vít ; Drápela, Jiří (referee) ; Topolánek, David (advisor)
This Master's thesis is focused on creating of an algorithm which calculates changes of negative-sequence voltages and currents from their instantaneous values. That allows to conduct localization of asymmetrical faults in MV network in line with the Vdip method, which is based on monitoring the changes of negative-sequence components at distribution substations and at a sub-transmission station. The algorithm is being developed in Matlab environment with continuous implementation of partial procedures which are being assessed and compared with each other. A study of phasor estimating methods is carried out with pointing out related problems which are mainly caused by Ripple control and deviation of system frequency from its nominal value. Optimization precautions are designed to mitigate these problems. For elimination of the Ripple control effects a method based on averaging is presented. The deviation of system frequency is dealt with by resampling the original data recordings. The analysis processes are tested by both simulation signals and real measured data. The optimized algorithm enables precise calculation of negative-sequence components changes which is the main contribution of this thesis. The constructed algorithm is used in verification of the Vdip method on physical model of MV network. For these purposes a simple distribution network is created within which ground faults on different places and with different resistances are realised. The results of localization are not convincing which is mainly caused by specific features of laboratory power line models which are constructed with heterogenous parameters.
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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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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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Localization of short-circuits on single side supplied HV line
Zíka, Jakub ; Jurák, Viktor (referee) ; Topolánek, David (advisor)
This bachelor‘s thesis deals with the localization of unilaterally fed short circuits on high voltage lines. The first part of the bachelor’s thesis deals with the research of the localization of unilaterally fed 1-Phase, 2-Phase and 3-Phase short circuits on the HV lines. Furthermore, individual types of short circuits are described here with suitable procedures for calculating the fault distance and definition of formulas for individual impedance loops. The second part of the bachelor’s thesis focuses on the implementation of these formulas for calculating the distance to the fault location. The input values of voltages and currents were simulated by a simple system model in the PSCAD program. Subsequently, a more detailed sensitivity analysis of individual types of short-circuits was carried out and possible detection of when individual calculation methods fail.
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Verification of the Vdip method on the physical model of the MV network
Krčál, Vít ; Drápela, Jiří (referee) ; Topolánek, David (advisor)
This Master's thesis is focused on creating of an algorithm which calculates changes of negative-sequence voltages and currents from their instantaneous values. That allows to conduct localization of asymmetrical faults in MV network in line with the Vdip method, which is based on monitoring the changes of negative-sequence components at distribution substations and at a sub-transmission station. The algorithm is being developed in Matlab environment with continuous implementation of partial procedures which are being assessed and compared with each other. A study of phasor estimating methods is carried out with pointing out related problems which are mainly caused by Ripple control and deviation of system frequency from its nominal value. Optimization precautions are designed to mitigate these problems. For elimination of the Ripple control effects a method based on averaging is presented. The deviation of system frequency is dealt with by resampling the original data recordings. The analysis processes are tested by both simulation signals and real measured data. The optimized algorithm enables precise calculation of negative-sequence components changes which is the main contribution of this thesis. The constructed algorithm is used in verification of the Vdip method on physical model of MV network. For these purposes a simple distribution network is created within which ground faults on different places and with different resistances are realised. The results of localization are not convincing which is mainly caused by specific features of laboratory power line models which are constructed with heterogenous parameters.
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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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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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