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Analysis of Mechanical Stress during Short Circuit in an Air-Insulated MV Switchgear
Bártů, Jan ; Bajánek, Tomáš (referee) ; Orságová, Jaroslava (advisor)
This Master thesis is based on problems of force effects of the magnetic field of short-circuit current. Firstly, I analysed the force action of the three phase busbars during the three-pole short circuit. The analysis was performed in the Ansys Maxwell program and I verified the correctness of the analysis by numerical calculation. The second practical part was executed for ABB company. The main task was to analyse the force effects of the short-circuit current in the HV switchgear with focusing on the arms and contact system of the circuit breaker. The simulations of the following configurations were performed in more details: three configurations of the simplified VD4 circuit breaker, two types of VD4 circuit-breaker contact systems and a linear circuit breaker configuration model. The objective was to calculate the forces acting on the current path of the arms and contact system of the VD4 circuit breaker during the three-phase short-circuit and to simulate the effects of forces on these current parts. For modelling of individual assemblies, calculations and simulations I used: SolidWorks 2014, Ansys Maxwell 16.0 and Ansys Workbench 14.5 programs. With SolidWorks 2014 3D CAD software were modelled simplified assemblies of circuit breakers and contact systems. These systems were imported into the Ansys Maxwell software, where the force effects of the magnetic field of the short-circuit current were calculated. In Ansys Workbench programme was simulated the effect of forces on the current circuit breakers. Moreover, the final deformations of the materials (with respect to the mechanical properties of the structure) were plotted. The analysis of force effects of the magnetic field was performed for the specified static short - circuit current value.
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Electrical installations in apartment building
Novotný, Jan ; Formánek, Marian (referee) ; Doležalová, Jana (advisor)
This bachelor's thesis deals with electrical wiring in apartment building. The aim is to describe the types of distribution networks, implementation possibilities of service lines, describe the individual parts of the wiring in the building and the principles of their implementation. Further describe basic electrical materials and to explain the design of artificial lighting. In the practical part the information applied to a particular apartment building, together with the calculation of the estimated annual energy consumption of flats. For the apartment building project is created in the form of engineering report and drawings.
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Rerating on the low voltage devices with a thermal trip unit
Trubák, Vojtěch ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This work is about bimetal trip unit used in circuit breakers. It focuses on how ambient temperature affects function of this tripping unit. In second chapter of this work, there are described thermal and dynamic effects of electric current. You can find there equations for calculation of temperature rise caused by electric current, its max temperature change and its process, also equations describing force, caused by electric current. In third chapter is short introduction of circuit breakers. There is description of their function, classification and construction. Finally there is description of residual current device. Fourth chapter of this work is focused on bimetals. There is described their function principle, ways of manufacture, used materials and its tripping characteristic. In fifth chapter, the circuit breaker 3VA12 is introduced, its electrical characteristics and its applications. Also, there is described principal of bimetal application as thermal trip unit. Sixth chapter is about procedure used to create model in CAD program Solidworks. You can find there individual pieces of current path and its addons connected together and forming model of circuit breaker. There are also showed modifications of the model, using thermal and conduction resistances. Last chapter is dedicated to results of rerating. There is final table showing correction koeficients of rated operational current and their comparison to real ones.
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Design of electrical installations in industrial buildings
Cabal, Jan ; Bátora, Branislav (referee) ; Toman, Petr (advisor)
The thesis deals with planning and proportioning of electrical installations within industrial objects. The theoretical part of the thesis looks into electrical installation planning and proportioning for all kinds of buildings. Basic terms related to projecting, project requirements, as well as the requirements on the designer, project documentation composition, and project documentation grades, are descibed. Furthermore, the text covers implementations of protection against electrical injuries, related legislative regulations and requirements, and finishes with the issues of electrical installations proportioning and protection. The practical part of the thesis contains a design of electrical installations for an industrial object involving high power wiring for a mechanical – technological part of the Zaječí water treatment plant. In addition to wiring proportioning and protection, the design involves a technical report, layout drawing and distributor RM1 plan.
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Seismic test of the switching devices on the low voltage
Dubský, Martin ; Mikyska, Kamil (referee) ; Dostál, Lukáš (advisor)
This work analyzes the seismic tests to valid technical starnards. Here is explained the term technical standard and written summary requirements for seismic resistance circuit breakers low voltage. The work includes devices suitable for the purpose and extreme laboratories dealing with seismic tests. The final section provides a draft test station with estimated economic return. Seismic tests are a very important part in the design of not only switching technology. It allows you to simulate the selected mechanical effects which may on the unit during operation or transportation to work and increase its reliability.
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Derating on the low voltage devices with a thermal trip unit
Dobrovolný, Jakub ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Electrical devices are secured as not to injure living creatures via electric current and damage or destroy machinery due to the effects of electric current. Circuit breaker is a device responsible for protection of an electrical circuit against damage. The main aim of thesis is the correct function of the thermal trip unit when it exposes to the thermal warming. The thermal trip unit is depended on heating of a bimetal before overcurrent flow. The goal of thesis is temperature and voltage drop profile from measured values. Verification of the measurement is done in SolidWorks Flow Simulation software. According to simulations are determined currents for correct function of the thermal trip unit in different temperatures of an environment. The most important result of the thesis is correct setting of the operating current in the circuit breaker.
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Affecting the function of thermal release of circuit-breakers for different connection systems
Lednický, Ján ; Vetiška, Vojtěch (referee) ; Dostál, Lukáš (advisor)
Right function of securing electrical installations is one of the most important factors preventing people, animals and electrical devices themselves from being electrocuted. Circuit breakers with an overcurrent tripping unit work with bimetal. When the bimetal is warmed up enough, it causes disconnection of circuit. This prevents people and animals from being harmed. To make overcurrent tripping unit work the right way, we have to minimise unnecessary disfunction factors caused by thermal thaw and Joule´s heat. This thesis is aimed at gaining general knowledge of heat transmission and transition of electrical current into heat. There are going to be made temperature-rise curves using all available connection sets to evaluate the impact of each one on the tripping unit. Then, a temperature profile of the circuit breaker will be made using a simulation made using SoildWorks Flow Simulation program. Finally, critical places of the current path will be observed.
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Tests of motor operarators for low voltage circuit-breakers
Mlynář, Zdeněk ; Polák, Jiří (referee) ; Valenta, Jiří (advisor)
Nowadays increasing demands for energy, safe use and automation in modern systems. The last two mentioned areas can now be relatively easily done using low voltage circuit breakers, along with accessories. The main element is a motor operator of circuit breaker that can operate fully automatically. But that could be the motor operator together with a circuit breaker is sold, it is necessary to fulfill a number of requirements. This work deals with their summarization, partitioning and sequential treatment of individual tests that are necessary for motor operator or required by customers.
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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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Usage of high-speed camera in the area of switching arc
Samohejl, Matěj ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor´s thesis is focused on optimizing recording of electrical switching arc in magnetic switches by high-speed camera. Measurements were performed on the circuit breaker 10B without removed side case, which was subsequently cowled by neutral density filter. The voltage and current of the circuit breaker contacts were acquired by measuring system of the Laboratory of switching arc diagnostics. The energy source was motor-generator with a nominal power 16 MVA and test bench consisting of a capacitors and inductors, which have been tuned to the resonance frequency of 50 Hz. Evaluation of the measurements was taken with regard to the brightness distribution levels of the record. Results showed that the mean brightness value varies on the square of the current passing through. For proper localization of the arc, it is necessary to appropriately set the camera exposure. The main problem usually is to darken the scene enough. It was found that it is necessary to take into account that brightness level change depends nonlinear on the exposure offset. The thesis gives a proposal to determine the exposure shift of the record. The possibility of usage high-speed camera to determine the temperature distribution in the arc using the brightness equiintensities was also designed. There are mentioned suggestions how to improve recording of the arc in circuit breakers, especially in the arrangement of the optical parts.
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