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The reactive-power compensation of the industrial consumer
Mišinger, Ondřej ; Bok, Jaromír (referee) ; Toman, Petr (advisor)
The work deals with reactive-power compensation (power factor correction = PFC) at low and medium voltage. The theoretical part is focused on explaining the basic concepts of power factor correction and the reasons why the PFC is made. There is stated the basic allocation of PFC. Attention is devoted mainly for detuned PFC, which is nowadays often used because of the large number of nonlinear loads installed by customers. There are listed also the basic computational relations. Moreover, there are described the basic elements of compensation devices, which are capacitors, detuning reactors, contactors and power factor regulators. The practical part is dealt with power factor compensation for a particular industrial customers. There are offered several variants of the technical implementation of the PFC. These various options are compared from both technical and economic terms.
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The quality of electric energy in a low voltage public supply networks
Macoszek, Pavel ; Šlezingr, Jan (referee) ; Bok, Jaromír (advisor)
This thesis contains four main chapters, which describe qualitative parameters of supply voltage and measurement and analysis received information. The theoretical part consists of three chapters. Characteristics of low voltage are described in the first chapter. Next chapter describes disturbing events, which have influence on quality supply voltage, reasons for their occurrence spreading in network, eventually arrangement leading to the disappearance of disturbing events on other electric appliances in network. Last theoretical chapter describes measuring instruments of supply voltage. The purpose of these theoretical parts is to introduce the reader into supply voltage quality issues and can be used for preparation of measurement and evaluation of acquired data under norm ČSN EN 50160 (Voltage characteristic of electricity supplied by public distribution systems). An analysis of real network is the last part of this thesis. There is applied acquired knowledge with the aim of analysis of real states of qualitative parameters of supply voltage in network.
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Usage rate watercourse
Görig, Michal ; Bok, Jaromír (referee) ; Matoušek, Antonín (advisor)
The Bachelor's project deals with a design of the small water power plant. In the first part of project there is a theoretic introduction about renewable energy sources and possibilities to electric energy produce from them, it describes possible types of water-power plants and their turbines. Next part is specialized for the choice of suitable area for building of mentioned small power plant. The design of machinery contains suitable turbine and generator. The electric part of water-power plant and connection to electric grid is also described. The last part values the investment to realization of this power plant.
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Optimalization of indirect resistance heating
Havránek, Miroslav ; Bok, Jaromír (referee) ; Lázničková, Ilona (advisor)
The indirect resistance heating is one of many ways of heating a melting charge. It is used in metallurgy, mostly for melting of soft metals. Its principle is a direct resistance heating in correspondence with the Joule´s law. The principle of indirect resistance heating is in generating of thermal energy in heating element and heat transferring this heat into the melting charge. The theoretical part of this Bachelor Work (the first three chapters) is focused to thermal energy generation and possibility of thermal transmittance. The fourth chapter is devoted to possibility of utilizing of the indirect heating in praxis. The simplest general design and calculation of a pot-type furnace for aluminium melting is done in the fifth chapter. There is a part in this chapter, which deals with the effectivity of the designed pot-type furnace and possibility of heating optimalization in case when indirect heating system is used. The input and calculated parameters of our designed furnace are summed up in the conclusion. There is also comparison of the designed furnace and a furnace readily available on the Czech market and stress on importance of optimalization of heating at indirect heating systems.
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Household heating systems
Ševčík, Ondřej ; Bok, Jaromír (referee) ; Bartošík, Tomáš (advisor)
Main goals of this bachelor thesis are economic evaluation of four chosen technologies of heating, and heating system design. Introduction deals with problem of heating in a family house, types of heating systems and main influences affecting the choice of heating system. The third chapter discusses main components of heating systems. Each component of the system is characterized and described. The most important parts include heating source, which are divided by type of fuel. The fourth chapter describes other possibilities of austerity meassures, which reduce heat loss and heating costs. There is a mention about government subsidies. The fifth chapter shows the shares of different heating sources, that are used in residential houses. In the last chapter, the computation of heat loss in the particular object is done. Based on the heat loss computation floor and radiator heating system is proposed. Four heat sources are chosen for the object (gas boiler, heat pump, biomass boiler and electric boiler with acumulation tank) and the purchase and the operating costs are computed. Conclusion of the chapter is devoted to the economic balance of the four heat sources and their comparison in the return of investment.
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Steady-state operation of 110 kV power line
Pastorek, Jaroslav ; Bok, Jaromír (referee) ; Blažek, Vladimír (advisor)
This Bachelor's thesis addresses the steady operation of 110 kV power lines. It is well known that these lines are used within the distribution system of very high voltage levels and are used to transfer large amounts of energy over long distances. The essential prerequisite for the transfer of such an amount of energy is to achieve the greatest efficiency possible. Therefore, there are methods developed, by which under known circumstances on one end of the line we can calculate the line ratios at the other end. These methods can be classified into exact, approximate and graphic methods. With approximate methods, T – element and ? – element, the most popular ones, are used. Only a brief description of the graphic method is given. Before the calculations of these methods, a procedure for determining various parameters of the external line is described. In the practical part, calculations based on the given example are listed. The example addresses calculation of ratios at the start of the line and ratios during short-circuit and freewheeling operation. The end contains a brief summary and comparison of the results. 100 kV lines can be either designed either as buried cables or external lines hanging from pylons. Buried cables are rarely used for 100 kV, so this Bachelor's thesis is focused on external lines.
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Current Transformers and Current Sensors Confrontation
Popek, Jiří ; Bok, Jaromír (referee) ; Topolánek, David (advisor)
Current transformers and current sensors are devices which are mostly used for current measurement in high voltage systems. This devices transform measured currents to range which are workable for measurement and protection devices. Current transformers have been using for current measurement since electric system was built. Current sensors are using for measurement after applying digital devices in their secondary circuits. Theoretical part includes fourth and fifth chapter. These chapters contain construction analysis and characteristic points for both devices. Practical part is in chapter six. This chapter consists results from laboratory measurement. Results are used for verification with theoretical part of the thesis. Accuracy class in nominal range and progress for measurement error in overcurrent range was verified for tested devices. Conclusion of this thesis comparing properties and summarises results from laboratory measurement.
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Utilization of renewable energy sources in Czech Republic
Kopička, Marek ; Bok, Jaromír (referee) ; Matoušek, Antonín (advisor)
This thesis deals with consideration of energy facilities structure in Czech Republic. It is depicted in it their evolution from point of: electric energy consumption, structures of energy facilities and electricity prices. Further, is here depicted a production of electric energy for the year 2009, from the point of: produce, sources, consumption and ratio of factories. Of course, the RSE (renewable sources of energy) effect and share of scope on this evolution and structure, is also mentioned here. The next part is pointed to basic description of each sources of electric energy. It is not mentioned here only factories which uses for it´s production renewable primary sources but also another types of factories. Their pros and cons are also summarized. The last part of this work is a thought of realization of fictive project, which could replace a part of steam power plants' share by producing electric energy through renewable sources. It is re-counted and suggested here a few possibilities of this realization from the point of needed installed power and approximate estimation of capital expenditure.
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The Appliances Immunity to Short Voltage Dips and Interruptions
Bok, Jaromír ; Beláň, Anton (referee) ; Santarius, Pavel (referee) ; Drápela, Jiří (advisor)
This Ph.D. thesis deals with problems about voltage dips and short voltage interruptions, generally named as voltage events, which origin in power supply networks and have a negative influence for all connected electric appliances. In this thesis single phase appliances are considered. These problems closely relate with area of electromagnetic compatibility which solve all questions about correct operation of different types of electric appliances during electromagnetic disturbances impact. Voltage events are ones of the many types of electromagnetic disturbances. The connection between disturbance sources and sensitive electric appliances is created by power supply lines. The immunity of electric appliances to voltage dips and short interruptions is currently tested via voltage dips with strictly defined parameters which are intended by class of electromagnetic environment in which the usage of electric appliance is recommended. During immunity tests the rectangular shape of voltage dips is preferred. The main descriptive parameters of testing voltage events are the residual voltage and the event time duration. But voltage dips and short interruptions defined by this way do not closely relate with parameters of real voltage dips and interruptions occurred in public supply system where parameters of voltage dips are variable. Moreover in the power supply system there are many of others voltage parameters which can have a significant influence to immunity level of connected electric appliances. This Ph.D. thesis also deals with finding more voltage event parameters. Although the voltage events occurrence in the power supply system is not limited and voltage events are considered only as informative voltage parameter it is important to monitor voltage events occurrence. The monitoring device has to be able to operate for ling time period and it has to detect parameters of voltage events with adequate accuracy. The accuracy of detected event parameters and the detection delay depends on the detection algorithm characteristics. That is why the part of this thesis relates with a comparison of several detection algorithms and their abilities to correct detection of voltage event parameters. The main purpose of this thesis is the proposal of connection between classification of voltage dips and short interruptions occurred in power supply system with the classification of electric appliances immunity to these voltage events. On the base of many of provided electric appliances immunity tests and also on the base of long time period voltage events monitoring the special compatibility levels are proposed in this thesis. The observation of proposed compatibility levels will bring the increasing level of reliable operation of all connected electric appliances.
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A Virtual Instrument for Measurement of Flicker
Cabala, Ľuboš ; Bok, Jaromír (referee) ; Šlezingr, Jan (advisor)
This thesis deals with the voltage fluctuation, its causes, resourses and affections on light sources. Further the posibbilities of the voltage fluctuations limitation are mentioned. This thesis also contains the decriptions of construction of UIE/EIC flickermeter on which bases the virtual flickermeter is programmed in the LabVIEW.
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