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Type test of a switching device
Knebl, Ladislav ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
Protection of the electrical ciruits in electrical installations by circuit breakers is the most common way of protecting circuits from overcurrents. In the low voltage installations, fuses were replaced by the circuit breakers. For this reason, it is important to put great emphases on their quality and user safety . This thesis deals with principle of the circuit breaker, its function, construction requirements and requirements for the type test, which the manufacturer needs to pass before release the device on market. These requrements are listed in Czech Technical Standard ČSN EN 60898-1. In this thesis, specific type of circuit breaker will be also described. Some sequences of tests described in the standard will be performed on that breaker.
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Switching arc plasma diagnostics by usage of two high-speed cameras
Buchta, Martin ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with an electrical arc formation and its properties. The thesis also describes some of the electrical devices and principles, which are used for arc extinction. It is mainly focused on design, construction and testing of model of the LV quenching system, which allows high speed cameras to record arc movement. Recorded images are then used to create three-dimensional reconstruction of the electric arc with help of created program 3DMaker. The final reconstruction is the output of this work.
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Design of a photovoltaic source connection to the grid
Rozmarín, Jiří ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
This bachelor thesis describes questions of photovoltaic power output of the part of distribution substation 22/0,4kV. The first part is focused on the simple description of sotware, which can be used in the design. The second and the fourth part deals with the actual design of substation, in the terms of its instrumentation, calculations for design and conductor sizing. The last part deals with the thorough check of the proposed power distribution and all the related equipment.
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Evaluation of a switching device behaviour during short-circuit current
Fendrych, Martin ; Dostál, Lukáš (referee) ; Valenta, Jiří (advisor)
At work, I focused on the principle of electric arc extinction in low voltage devices. I particularly focused on the issue of magnetic switches. Next, I processed by the theory site issue of contact system in magnetic switches. In the practical part of my work, I was testing modular low voltage circuit breaker type of 2B and 10B. Testing was carried out in the laboratory of switchgear. I observed the movement of the contact and electric arc, which was burned between them and conductor wall. Observation was recorded by using a high-speed camera and an oscilloscope. Of acquired waveforms, I evaluated the dynamics of contacts, electric arc length and the value of the arc voltage for different moments.
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Creation of LabView application for automatic measurement of switchgear temperature rise
Kopunec, Vít ; Huzlík, Rostislav (referee) ; Valenta, Jiří (advisor)
The aim of this work is to create an automated measurement of the temperature increase of electrical devices using the graphical programming environment of LabVIEW. To measure the temperature increase, up to four thermocouples are used of any type. The final .vi file must meet the requirements for the particular option settings; before running a measurement. On the front panel .vi file, is displayed the following configuration elements: time measurement, number of measurements, thermocouple type and amplification. The programme measures the voltage of the thermocouples, recalculates the value of voltage to the temperature, measures the values to write to a file with a txt extension, and writes values into the tables, constructing useful graphical information of physical measurements.
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Electrodynamic forces acting on moving contact of electrical apparatus
Šic, Pavel ; Valenta, Jiří (referee) ; Bušov, Bohuslav (advisor)
This master’s thesis is focused on calculation, simulation and experimental verification of electrodynamic forces acting upon movable contact piece of MCCB and experimental current carrying path. A short description of low voltage circuit breakers is briefly discussed in first chapter. Second chapter is focused upon contact system analysis of particular MCCB with thermomagnetic trigger. A hardness of contact materials is briefly described. A detailed analytical calculations were used to determine electrodynamic forces in MCCB. A FEM simulation in ANSYS Maxwell was carried out for comparison with analytical results. An experimental apparatus was designed and built for verification of constriction repulsion force, so called Holm’s force. A series of measurements is subsequently performed on proposed apparatus and results are compared with results from previous chapters.
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Switching mechanism in the molded case circuit breaker
Mejzlík, Tomáš ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This paper deals with mechanical switch in circuit breaker designed for low voltage. The goal of this thesis was to analyze switching mechanism both theoretically and practically. Theoretical analysis consist of study different types of switching mechanism and analytical calculations of acceleration speed and trajectory. Practical analysis has been made taking a video with high speed camera of real switching mechanism of a circuit breaker and software analysis of the data. The next part of a thesis is about 3D modeling, animating and simulating of a switchgear switching mechanism.
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Analysis of electrodynamic forces in electrcal apparatus
Dobrovolný, Jan ; Valenta, Jiří (referee) ; Šimek, David (advisor)
The master thesis deals with the phenomena called electro-dynamic force in the electrical apparatus. Nowadays, there are high requirements for electrical devices. The devices and especially their contacts are subject to high demands on reliability, reliability and mechanical durability. The electro-dynamic forces caused by the passage of electric current mechanically deform the current path. The design of the electrical apparatus must take these forces into account. Equations for electro-dynamic forces calculation are presented. In master thesis, individual parts of the current path are derived and described. Various configurations and designs of the current path are solved. The thesis also deals with the issue of forces in electrical contacts. Individual theoretical equations are then applied to a particular disconnector QAK, made by company IVEP, a.s. Parts of the disconnector were redrawn into 3D program SolidWorks. The model was analysed in program ANSYS Maxwell. The thesis compares the achieved results of analytical equations and numerical simulations.
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Arc optical diagnostics
Čermák, Jiří ; Valenta, Jiří (referee) ; Dohnal, Petr (advisor)
The aim of this bachelor thesis is to sort out the individual types of electric discharges, explain the ionization inside the plazma of the electric arc and the elucidation of the energetic balance inside the plazma. The electric arc is an undesirable and hardly predictable phenomenon occurring in switching devices during switching on and switching off the electric circuit. Some older methods of image processing obtained by a high-speed camera are also mentioned. Based on the images obtained from the camera, it is possible to make an equidensity or an equidensitogram that is used to monitor the arc in a quenching chamber. The second part includes the description of an experiment performed in a laboratory and the description of the high-speed camera used during this experiment. A modern method of the image processing using software Matlab is also described. An equidensitogram showing different levels of radioation was made in Matlab from the obtained images.
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Analysis of the stator and rotor pack termination effect on the synchronous machine by FEM
Michailidis, Petr ; Valenta, Jiří (referee) ; Skalka, Miroslav (advisor)
This thesis deals with simulation’s possibilities of the electromagnetic fields in electrical machines. A finite element method is the final element technique. The content of this thesis is a model and mesh creation and electromagnetic simulation of synchronous machine. The stator and rotor pack termination effect on the synchronous machine.is analyzed by finite element method in ANSYS program. The type of the stator termination pack is described by four segments. The magnetic field distribution is deformed due to the material properties of used segments. In the next part a methodics of mesh creation is shown. The mesh quality (in term of elements number and elements shape) is important due to the solution accuracy and speed.
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