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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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Thermal calculation in design of resistance and induction devices
Krčál, Vít ; Foral, Štěpán (referee) ; Lázničková, Ilona (advisor)
This bachelor’s thesis focuses on thermal calculation of electric heating device and related theory. Selected topics in electric heating technology are explained, followed by the calculation in design of a crucible furnace and its automation using a computer program. The theoretical part first deals with the heat transfer mechanisms and their mathematical description. Further on, the thesis describes how heat is created in resistance and induction heating devices and mentions applications of these types of heating. The main part of the thesis focuses on the thermal calculation of the resistance crucible furnace for aluminium melting. The calculation relates to a cylinder-shaped model of the furnace with determined structure and deals mostly with heat loss, electric power input, thermal efficiency and design of heating elements. The calculation is achieved only in general and it is subsequently automated in Microsoft Office Excel® application. The computer program, which is also a part of the thesis, allows user to change input parameters and see how it affects results of the calculation. In the last chapter, an example of calculation for specific numeric data is presented. The main goal of the thesis is to automate the calculation. That can save some time while calculating and designing a crucible furnace.
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Magnetic field measurement with gaussmeter FW BELL 4090
Urbánek, Pavel ; Krčál, Vít (referee) ; Vyčítal, Václav (advisor)
This thesis focuses on the basics of magnetic field and its measurement. The field will be measured with the FW Bell 4090 instrument and depending on the success and accuracy of the measurements, the bachelor thesis should include a possible integration into teaching. The measurement of the magnetic field will be adjusted to verify whether the device parameters in accordance to the manual. The most important attributes are the accuracy of single field or multi-field measurements, the accuracy of measurements in all axes of the instrument, and measurements over a given frequency range.
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Optimization Of Mesh Network Configuration For Reduction Of Short Circuit Currents
Krcal, Vit
This paper deals with LV mesh network reconfiguration in order to minimize short circuitcurrents. The reconfiguration rests in switching off selected network elements leading to increase ofshort circuit impedances in LV nodes. For optimal configuration, an algorithm of sequential disconnectingof elements is proposed, based on load flow and short circuit calculations. The reconfigurationprocedure is applied to a model of a mesh MV/LV network. Reduction of short circuit currentsin this network is presented, capturing impact of each step of the sequence. Based on the presentedresults, deploying other measures and further development of the proposed algorithm are discussed.
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A Validation Tool For The Vdip Method For Earth Faults Localization And Its Evaluation
Krčál, Vít
This paper describes a process of evaluation of the Vdip method for earth faults localization. For purposes of method validation, PSCAD simulation are used. In PSCAD, fault occurrences are simulated and COMTRADE format records are created. The fault records are then processed in Matlab with evaluation of the fault location. This process and can be useful for testing before the realworld application and can serve as reference.
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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.
|
|
|
Thermal calculation in design of resistance and induction devices
Krčál, Vít ; Foral, Štěpán (referee) ; Lázničková, Ilona (advisor)
This bachelor’s thesis focuses on thermal calculation of electric heating device and related theory. Selected topics in electric heating technology are explained, followed by the calculation in design of a crucible furnace and its automation using a computer program. The theoretical part first deals with the heat transfer mechanisms and their mathematical description. Further on, the thesis describes how heat is created in resistance and induction heating devices and mentions applications of these types of heating. The main part of the thesis focuses on the thermal calculation of the resistance crucible furnace for aluminium melting. The calculation relates to a cylinder-shaped model of the furnace with determined structure and deals mostly with heat loss, electric power input, thermal efficiency and design of heating elements. The calculation is achieved only in general and it is subsequently automated in Microsoft Office Excel® application. The computer program, which is also a part of the thesis, allows user to change input parameters and see how it affects results of the calculation. In the last chapter, an example of calculation for specific numeric data is presented. The main goal of the thesis is to automate the calculation. That can save some time while calculating and designing a crucible furnace.
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