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Replacement of electromechanical protections in TNS Vraňany
Čechová, Karolína ; Šiler, Michal (referee) ; Orságová, Jaroslava (advisor)
The reconstruction of the traction substation Vraňany currently involves only the replacement of power oil transformers. The main reason for their replacement is the fact that the power transformers have already exceeded their designed lifecycle. According to an investor requirement, only the transformer replacement is considered, however, a new system of protection is not included. Even though the fault-free operation of power transformers is closely related to ensuring a reliable and safe electric power supply. The main aim of the thesis is to design a new system of protection for power transformers to replace the present one. In the theoretical part of the thesis is described the current state of the traction substation along with a calculation of short circuit current ratios and their comparison with the new ones considering the installation of the new power transformers. In the next part are inspected instrument current transformers if they comply with the requirements for the new protection system. The practical part of the thesis focuses on the selection of protection relay, calculation of the primary setting for selected protection functions, and subsequently conducting their functional tests. In conclusion, the economic part of the planned investment is estimated.
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LOSSES IN MEDIUM VOLTAGE CURRENT TRANSFORMERS
Bajánková, Denisa ; Langerová, Petra (referee) ; Baumgartnerová, Alena (advisor)
Tato bakalářská práce umožňuje nahlédnout do problematiky ztrát u přístrojových transformátorů proudu vysokého napětí. Přístrojové transformátory proudu představují velmi důležitou součást elektrických zařízení, slouží k transformování měřených proudů na standardní hodnoty, které měřicí a jistící přístroje mohou zpracovat. Je důležité, aby tyto proudy byly převáděny s co nejvyšší přesností. Teoretická část práce se zaměřuje na popis přístrojových transformátorů proudu a analýzu jednotlivých ztrát u transformátoru. Praktická část je obsažena v deváté kapitole, má za cíl ověřit teoretické poznatky práce a popisuje laboratorní měření.
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Draft sources 1000A AC current sensors for calibration
Klimeš, Jan ; Vetiška, Vojtěch (referee) ; Dohnal, Petr (advisor)
This bachelor thesis deals with design and construction of device for precise measurement of 1000 A alternate current. This thesis theoretically discusses the possibilities of conventional solutions, such as current transformers, as well as modern methods in the form of current sensors. The output of this thesis is a solution of problems with accuracy and discussion of other possible ways to reduce systematic error. The thesis discusses structure of the current transformer, the digitalizing of the signal and its usage as an input for engineering units. The device is then tested for final accuracy.
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Differential Protection for Power Transformer
Bukvišová, Zuzana ; Wasserbauer, Vojtěch (referee) ; Orságová, Jaroslava (advisor)
This thesis explores power transformer protection and focuses on differential protection. It attempts to explain its principles and operating characteristic settings. The measurement was executed on devices SPAD 346 C and REF542plus, which can be used for differential protection. At the end, there is a comparison of results of operating characteristic measurement on both devices. Their function was tested at different cases, specifically when the differential current occurs in all phases or just one. The thesis includes a comparison of reaction times under fast increase of current. OMICRON CMC 256 plus was used as the test device. The data obtained by the measurement are processed in tables and charts.
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Primary testing of the protection relays
Macek, Vratislav ; Topolánek, David (referee) ; Toman, Petr (advisor)
The main subject of this bachelor’s thesis is the creation of laboratory task on the issue of primary injection testing of the protection relays. The thesis is made up of two parts: theoretical and practical. In theoretical part there are information concerning the issue of protecting. One of them the meaning and relay function, requirements applicable on them, failure states, which may arise on the device operation, description of instrument transformers and methods of testing relays. In practical part is created laboratory task on the issue of primary injection testing of overcurrent relay, of which will demonstrate the influence of load current transformer to its function. In task are used Overcurrent and Earth-fault protection REJ 525A and measuring instrument Omicron CPC 100.
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Analysis of current lead joints inside HV current transformers
Pálka, Marek ; Váňo, Pavel (referee) ; Drápela, Jiří (advisor)
The main focus of the dissertation thesis is determine the size of the fastening screw connection and fastening torque of the connection, which will be applied during assembly of the instrument current transformers and sensors. The large part of thesis is an experimental measurement of the proposed configurations of connections and modelling (simulating) certain model of connections in Ansys and SolidWorks analysis programs. The result of the dissertation will be design of tightening of the connection according to transient resistance and thermal losses.
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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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Current transformers 12kV, 4000 / / 5/5A
Šumberák, David ; Vaněk, Jaromír (referee) ; Dostál, Lukáš (advisor)
This master´s thesis describes the development proposal and production of instrument current transformer in one turn primary winding with 4000//5/5 A transfer. The thesis involves a theoretical analysis, a numerical calculation, a developmental 3D model, corresponding simulations and a standard testing of the transformers. There is a complete written description of measuring current transformer cycle from the development to the production. The transformer development and production works were collaborated with the company KPB Intra s.r.o. The company engages in development, production and sale of these kinds of instrument transformers in the Czech Republic and foreign markets.
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Comparison of Instrument Transformer and Sensor Applications in Feeder Terminal REF 542plus
Hrycík, Tomáš ; Majer, Karol (referee) ; Orságová, Jaroslava (advisor)
The aim of this Master´s thesis is use of instrument transformers and sensors on field of industry protection. We will compare current and voltage transformers, current sensor – based on Rogowski coil, voltage sensor – based on voltage divider. By this measure devices, we can monitoring values of analog quantities in medium voltage switchgear. It is impossible to compare, measure and analyze without this measure devices. There is protection terminal REF542plus, which can compile this values. The REF542plus ability are measuring, monitoring, remote control and protection. First, we will discuss about theory of sensors and convential instrument transformers and analysis of analog signal. We will compare analog input channel on sensor´s analog module and transformer´s analog module. There are few differences between type of analog modules. For analog signal analysis are important frequency filters and Analog/ Digital Convertor (sigma-delta). We will describe functions and options of REF542plus. In practical part of this project, we will test protection functions of protection terminal. First, protection terminal will be connected to sensors. Second protection terminal will be connected to transformers. For testing we chose Earth-fault directional protection and differential protection. We will make only secondary tests. That´s mean, input analog quantities to REF542plus will be simulated by tester. In all we will verify quality of protection. We will focus on lower settings of protection and we will inject protection by low current. Objectives are testing of trip characteristics and measuring of trip time.
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