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1
Karlsson, Svante. "Power Transformer Monitoring and Diagnosis using Transformer Explorer." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-280958.
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Power transformers are one of the most expensive and vital components in the power system. A sudden failure could be a very costly process for both the transformer owner and the society. Several monitoring and diagnostic techniques have been developed over the last decades to detect incipient transformer problems at an early stage, so that planned outages for maintenance and reparation can be carried out in time. However, the majority of these methods are only secondary indicators which do not address the transformers fundamental function: to transfer electric energy between different voltage levels with turn ratio, short-circuit impedance and power loss within acceptable limits. Transformer Explorer is a concept developed by ABB which utilizes ordinary current and voltage signals available in the substation to extract transformer fundamental parameters such as: turn ratio, magnetizing current, impedance and power loss, which has significant diagnostic value. By estimating these parameters the method should be able to detect a number of problems related to the windings and the magnetic circuit of the transformer. Transformer Explorer is expected to find it's application in two different versions, either as an permanent on-line monitoring and diagnostic tool or as a short-time version for temporary measurements. The thesis could be divided into three main parts. The first one focusing on a quantitative study trying to answer questions regarding the concepts feasibility when the temporary version is used. The second part is about optimizing and improving the procedure by which the fundamental parameters are estimated. In the last part, a new method for reducing the impact of errors introduced by the acquisition system on the estimated power loss is proposed. All the investigations related to the three topics covered in this thesis showed interesting and promising results.
2
Lapthorn, Andrew Craig. "High Temperature Superconducting Partial Core Transformers." Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/7130.
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The thesis begins by providing an introduction to transformer theory. An ideal transformer is examined first, followed by full core transformer theory. The partial core transformer is then introduced and compared to the full core design. An introduction to superconductors is then presented where a simplified theory of superconductivity is given. High temperature superconductors are then examined including their physical structure, superconducting properties and the design of the superconducting wire.
The early development of high temperature superconducting partial core transformers at the University of Canterbury is then examined. Early partial core development is discussed followed by some material testing at cryogenic temperatures. This work lead into the development of the first high temperature superconducting partial core transformer. This transformer failed during testing and an examination of the failure mechanisms is presented. The results of the failure investigation prompted an alternative winding insulation design which was implemented in a full core superconducting transformer.
The modelling used to design a high temperature superconducting partial core transformer is then presented. Based upon the reverse design method, the modelling is used to determine the components of the Steinmetz equivalent transformer circuit. The modelling includes a combination of circuit theory and finite element analysis. An ac loss model for high temperature superconductors is also presented.
A new 15 kVA, 230-230V high temperature superconducting partial core transformer was designed, built and tested. The windings are layer wound with first generation Bi2223 high temperature superconductor. The modelling was used to predict the performance of the transformer as well as the ac losses of the high temperature superconductor. A series of electrical tests were performed on the transformer including open circuit, short circuit, resistive load, overload, ac withstand voltage and fault ride through tests. The test results are compared with the model. The transformer was found to be 98.2% efficient at rated power with 2.86% voltage regulation.
3
Liew, Ming Chuen. "Reverse design transformer modelling technique with particular application to partial core transformers." Thesis, University of Canterbury. Electrical and Electronic Engineering, 2001. http://hdl.handle.net/10092/2123.
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This thesis first describes the conventional transformer design method used for design
iron-core transformers. Limitations associated with this design method is highlighted.
In this thesis, an alternative transformer design method is presented. It is called the
reverse design method. This new design technique is compared against the conventional
design method, and validated with experimental results.
The reverse design method is applied to partial core transformers. Modifications made
to accommodate full-core equivalent circuit components to partial core transformers
are discussed. Particular attention is given to the derivation of core loss resistance,
core magnetising reactance and winding leakage reactances. The new reverse design
partial core model is applied at 50Hz normal operating temperature applications. The
model is verified with experimental results.
Next the reverse design model is applied to transformers when immersed in liquid nitrogen.
The accuracy of the model derived previously for normal operating temperatures
is investigated. Necessary modifications are made to the model. The corrected model
is again justified with experimental results.
Finally, the model is used for the harmonic frequency analysis of partial core transformers.
Capacitive components are included as part of the analysis. Frequency responses
of transformers with relatively low turn ratio are analysed, followed by high voltage
partial core transformers with large turn ratio. Comparisons are made between the
model calculated and test results.
4
Reyes, Rosa Maria Barragan. "Heat transformer studies." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386347.
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5
White, Cynthia Quinn. "The Transformer Station." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64190.
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6
Fontana, Christian. "Solid State Transformer." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3424940.
Full textAbstract:
The Solid State Transformer (SST) is an emerging solution that can advantageously substitute the conventional transformer, thanks to its capabilities. Furthermore, it is a multi-functional equipment that offers:
- conditioning of the power flow, whether of DC or AC form;
- reduced size and weight thanks to the high frequency transformer;
- good voltage regulating capabilities;
- no diffusion of voltage swell or sag thanks to the DC link (if any);
- power factor correction;
- fast fault detection and protection;
- capability to maintain the output feed for a time (hold up time) thanks to the DC link capacitors;
Moreover, it offers the conventional transformer properties:
- galvanic isolation between input and output;
- step up/down of the input voltage;
The SST capabilities make this technology an important solution to solve the current and future issues of the grid. The reduced weight and size allow getting high performances in the traction systems. The bidirectional power flow capabilities allow the connection and management of renewable energy sources (RES) with the grid and different loads, connected to AC side or, if present, to DC link.<br>Il trasformatore a stato solido (SST) è un emergente tecnologia che può sostituire i trasformatori convenzionali, apportando notevoli vantaggi grazie alle sue potenzialità e funzionalità.
Tra le più importanti abbiamo:
-condizionamento del flusso di potenza, sia DC che in AC;
-ridotte dimensioni e peso, grazie all'uso di un trasformatore in alta frequenza;
-ottima regolazione della tensione;
-limita diffusione di buchi di tensione;
-correzione del fattore di potenza;
-hold up time funzionalità;
-isolamento galvanico.
Grazie a queste funzionalità questa tecnologia diventa molto importante per poter affrontare problemi, presenti e futuri, legati alla gestione della rete elettrica. La possibilità di gestire il flusso di energia e la bidirezionalità del flusso di potenza consentono di facilitare l'integrazione delle risorse rinnovabili con la rete elettrica. Inoltre, la riduzione dipeso e dimensioni consentono di ottenere alte performance in sistemi usati per la trazione.
7
Mao, Peilin. "Power transformer fault diagnosis based on wavelet transform and artificial neural network." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760740.
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8
Zhong, Ming. "Partial core power transformer." Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/7537.
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This thesis describes the design, construction, and testing of a 15kVA, 11kV/230V partial
core power transformer (PCPT) for continuous operation. While applications for the partial
core transformer have been developed for many years, the concept of constructing a partial
core transformer, from conventional copper windings, as a power transformer has not been
investigated, specifically to have a continuous operation. In this thesis, this concept has been
investigated and tested.
The first part of the research involved creating a computer program to model the physical
dimensions and the electrical performance of a partial core transformer, based on the existing
partial core transformer models.
Also, since the hot-spot temperature is the key factor for limiting the power rating of the
PCPT, the second part of the research investigates a thermal model to simulate the change of
the hot-spot temperature for the designed PCPT. The cooling fluid of the PCPT applied in
this project was BIOTEMP®. The original thermal model used was from the IEEE Guide for
Loading Mineral-Oil-Immersed transformer. However, some changes to the original thermal
model had to be made since the original model does not include BIOTEMP® as a type of
cooling fluid. The constructed partial core transformer was tested to determine its hot-spot
temperature when it is immersed by BIOTEMP®, and the results compared with the thermal
model.
The third part of the research involved using both the electrical model and the thermal model
to design a PCPT. The PCPT was tested to obtain the actual electrical and the thermal
performance for the PCPT.
The overall performance of the PCPT was very close to the model estimation. However,
cooling of the PCPT was not sufficient to allow the PCPT to operate at the design rated load
for continuous operation. Therefore, the PCPT was down rated from 15kVA to maintain the
hot-spot temperature at 100°C for continuous operation. The actual rating of the PCPT is 80%
of the original power rating, which is 12kVA.
9
Chew, En Phin. "Superconducting Transformer Design and Construction." Thesis, University of Canterbury. Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/4977.
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This thesis first outlines the testing undertaken on a partial core superconducting
transformer under open circuit, short circuit, full load and endurance test conditions.
During the endurance test, a failure occurred after 1 minute and 35 seconds. During the
failure, voltage dipping and rapid liquid nitrogen boil off was observed. This prompted
a failure investigation which concluded that the lack of cooling in the windings was the
most probable cause to the failure.
Full core transformer and superconductor theories are then introduced. A copper
winding transformer model, based on a Steinmetz equivalent circuit and a reverse
design method, is described. A superconductor loss model which outlines the different
types of losses experienced under AC conditions is used to determine the resistance
of the windings in the Steinmetz equivalent circuit. This resistance changes with the
magnitude of current and the strength of the magnetic field that is present in the gaps
between each layer of the windings. An alternative leakage flux model is then presented,
where the flux is modelled based on the combination of the reluctance of the core and
the air surrounding the windings. Based on these theories, an iterative algorithm to
calculate the resistance of the superconductor is developed.
A new design of a 15kVA single phase full core superconducting transformer, operating
in liquid nitrogen, is presented. The issues with building the superconducting
transformer are outlined. First, a copper mockup of the superconducting transformer
was designed where the mockup would have the same tape and winding dimensions
as the superconducting transformer, which means the same core can be used for two
different sets of windings. This led to designing a core that could be easily taken apart
as well as reassembled. Construction of the core, the copper windings and the superconductor
windings ensued. The process of cutting the core laminations, insulating the
copper and superconductor tapes, and making the steel fasteners and terminations are
described.
The copper mockup and superconducting transformers was then tested under open
circuit, short circuit, different load and endurance conditions at both liquid nitrogen
and room temperatures. These test results were then compared with the those from
two models. The comparison showed a significant inaccuracy in the reactances in
the models. This introduced a correction factor into the superconductor model which
ii
made it more accurate. However, further work is required to explain and quantify the
correction factors for the copper transformer model under different load conditions.
10
Zhang, Xingxing. "STRANDED CORE TRANSFORMER LOSS ANALYSIS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/533.
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We will present the approaches used to investigating the power loss for the stranded core transformers. One advantage of using stranded core is to reduce power loss or enhance transformer efficiency. One difficulty in the modeling of this type of transformer is that the core is not solid (there are small gaps between core wires due to circular cross section). A two dimensional finite element method with nodal basis function for magnetostatic field was developed to study the effects of the small gaps between core wires. The magnetic flux densities are compared for the uniform (solid) cores and the stranded cores for various permeability values. The effects of different air gap dimensions in stranded core to the magnitude of magnetic flux density were also discussed. The results of the two dimensional study were applied to modify the B-H curves in a 3D simulation with an equivalent simplified uniformed core transformer model via Ansoft Maxwell 3D. This is achieved by output the magnitude of magnetic flux density at fixed points of mesh center. The total core loss of a transformer was predicted by integration of the losses of all elements.
11
Wilson, Gordon. "Characterisation of mineral transformer oil." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392140.
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12
Zandberg, Hermanus Andries Jakobus. "Wireless transformer condition monitoring system." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1186.
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The Department of Electrical Engineering in fulfilment of the
requirements for the Magister Technologiae in Electrical
Engineering at the
Cape Peninsula University of Technology
November 2013<br>Pole mounted transformers (PMT) in rural areas present an opportunity for local
utilities to do current monitoring on these systems. These transformers are exposed to
abnormal amounts of stress due to the vast power demand in these areas. The aim of
this study is to develop a more cost-effective condition monitoring system. Transformer
current monitoring can be a dangerous practice if not done by suitably trained utility
electricians. Hence this study is partly aimed at the elimination of hazardous working
environments associated with manual electrical measurements.
An investigation to determine a safe and cost-effective way to obtain the electrical
measurements required from PMTs is undertaken. Although current measurements can
be done with a current clamp-on meter, these measurements still take place at the
phases of the transformer and are unsafe. The possibility of implementing wireless data
gathering on current clamp-on meters is therefore investigated. This is made possible by
a wireless sensor node (WSN) which gathers information and transmits it wirelessly to
a WSN base station.
This wireless solution is battery powered, necessitating battery replacements, therefore
leading to the investigation of magnetic fields, magnetic materials and magnetic
induction. A current clamp able to generate a high voltage (HV) output with minimal
magnetic field strength is developed. The magnetic fields produced by the transformer’s
phase cables are used to generate an alternating voltage. With the help of a
microcontroller and an energy harvesting circuit, this voltage is converted and used to
charge supercapacitors. The magnetic fields are also used to determine the current flow
in the transformer phase cables when the device is not in energy harvesting mode.
The device will then undergo comprehensive laboratory testing to determine its
accuracy and durability, and is then used to do ‘real life’ current measurements, the
results of which are compared against an off-the-shelf current monitoring device.
13
Cho, Sung Don. "Parameter estimation for transformer modeling /." Available online. Click here, 2002. http://sunshine.lib.mtu.edu/ETD/DISS/chosd/SungCho.pdf.
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14
Edwards, John. "Magnetic flux based transformer model /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16945.pdf.
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15
Hardie, Stewart Ramon. "A Prototype Transformer Partial Discharge Detection System." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1114.
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Increased pressure on high voltage power distribution components has been created in recent years by a demand to lower costs and extend equipment lifetimes. This has led to a need for condition based maintenance, which requires a continuous knowledge of equipment health. Power transformers are a vital component in a power distribution network. However, there are currently no established techniques to accurately monitor and diagnose faults in real-time while the transformer is on-line. A major factor in the degradation of power transformer insulation is partial discharging. Left unattended, partial discharges (PDs) will eventually cause complete insulation failure. PDs generate a variety of signals, including electrical pulses that travel through the windings of the transformer to the terminals. A difficulty with detecting these pulses in an on-line environment is that they can be masked by external electrical interference. This thesis develops a method for identifying PD pulses and determining the number of PD sources while the transformer is on-line and subject to external interference. The partial discharge detection system (PDDS) acquires electrical signals with current and voltage transducers that are placed on the transformer bushings, making it unnecessary to disconnect or open the transformer. These signals are filtered to prevent aliasing and to attenuate the power frequency, and then digitised and analysed in Matlab, a numerical processing software package. Arbitrary narrowband interference is removed with an automated Fourier domain threshold filter. Internal PD pulses are separated from stochastic wideband pulse interference using directional coupling, which is a technique that simultaneously analyses the current and voltage signals from a bushing. To improve performance of this stage, the continuous wavelet transform is used to discriminate time and frequency information. This provides the additional advantage of preserving the waveshapes of the PD pulses for later analysis. PD pulses originating within the transformer have their waveshapes distorted when travelling though the windings. The differentiation of waveshape distortion of pulses from multiple physical sources is used as an input to a neural network to group pulses from the same source. This allows phase resolved PD analysis to be presented for each PD source, for instance, as phase/magnitude/count plots. The neural network requires no prior knowledge of the transformer or pulse waveshapes. The thesis begins with a review of current techniques and trends for power transformer monitoring and diagnosis. The description of transducers and filters is followed by an explanation of each of the signal processing steps. Two transformers were used to conduct testing of the PDDS. The first transformer was opened and modified so that internal PDs could be simulated by injecting artificial pulses. Two test scenarios were created and the performance of the PDDS was recorded. The PDDS identified and extracted a high rate of simulated PDs and correctly allocated the pulses into PD source groups. A second identically constructed transformer was energised and analysed for any natural PDs while external interference was present. It was found to have a significant natural PD source.
16
Hogg, Robert Andrew. "An adaptive, microprocessor based transformer differential relay with harmonic restraint and transformer tap changer detection." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315575.
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Bergsåker, Claudia. "Impact of transformer core size on the reactive power requirement of power transformers due to GIC." Thesis, KTH, Elektroteknisk teori och konstruktion, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157347.
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Geomagnetically induced currents (GIC) are a natural phenomenon which arises due to solar storms. During a solar storm, large amounts of magnetized plasma are ejected from the surface of the sun. When this plasma reaches earth, it causes fluctuations in the geomagnetic field. Such fluctuations may induce DC over-currents in long transmission lines. These currents affect the transmission system several dierent ways; In particular high voltage transformers are sensitive to GIC. When the over-current flows through the transformer windings the reactive power absorption of the transformer increases, which may lead to voltage instability in the power system. For this project, the main issue has been to determine whether or not an increase in the size of the transformer core leads to the reactive power absorption being less sensitive to GIC. In order to investigate this issue a recently developed transformer model has been used; the Hybrid transformer model. This model combines the principle of duality with a matrix representation of the transformer. The Hybrid transformer model, which has recently been implemented in the power system simulations software PSCAD, has been used to simulate GIC events in transformers of varying core sizes. The results from these simulations indicate that a larger transformer core is associated with a smaller increase in reactive power absorption during a GIC event. It is also clear that the reactive power absorption as a function of GIC magnitude is a non-linear function when the Hybrid transformer model is applied. This function has previously been considered a linear function.<br>Geomagnetiskt inducerade strömmar (GIC) är ett naturfenomen som uppstår till följd av solstormar. Vid en solstorm kastas stora mängder magnetiserad plasma ut från solens yta, och när denna plasma når jorden uppstår uktuationer i det jordmagnetiska fältet. Detta kan leda till att DCstr ömmar induceras i långa transmissionsledsningar. Dessa överströmmar påverkar kraftsystemet på era olika sätt, bland annat har de en stor påverkan på transformatorer. Då överströmmen yter genom transformatorlindningarna ökar det reaktiva eektuttaget för transformatorn, vilket kan leda till spänningsinstabilitet i systemet. En fråga som legat till grund för detta projekt är huruvida en ökning av transformatorkärnans storlek gör transformatorns reaktiva eektuttag mindre känsligt för GIC. För att undersöka detta har en ny transformatormodell använts; den såkallade hybridmodellen som kombinerar dualitetsprincipen med en matrisrepresentation av transformatorn. Denna modell, som nyligen implementerats i simuleringsprogrammet PSCAD, har använts för att simulera GIC i transformatorer med kärnor av olika storlekar. Resultaten från dessa simuleringar indikerar att större transformatorkärna medför mindre förändring av det reaktiva eektuttaget när transformatorn utsätts för GIC. Det är även tydligt att det reaktiva eektuttaget som funktion av GIC är en icke-linjär funktion när hybridmodellen används. Denna funktion har tidigare ansetts vara linjär.
18
Adabi, Firouzjaee Mohammad Ebrahim. "Advanced modeling of solid state transformer." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/461451.
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The solid state transformer (SST) is seen as a proper replacement of the conventional iron-and-copper transformer in the future smart grid . The SST offers several benefits (e.g. enhanced power quality performance or reactive power control at both primary and secondary sides) that can be of paramount importance for the development of the smart grid .
This research focuses on the development and implementation of an advanced model of a three stage bidirectional SST in Matlab/Simulink. The goal is to obtain an realistic SST model (i.e. as close to the real SST as possible) that could duplicate the performance of a real MV/LV SST. This considered design consists of three main stages: medium voltage (MV) stage, isolation stage, and low voltage (LV) stage. When the power flows from the MV side to the LV side, the input power-frequency ac voltage is converted into a MV dc voltage by the three-phase ac/dc converter, which in such case works as rectifier. The isolation stage, which includes a high-frequency transformer (HFT) and the two corresponding MV- and LV-side converters, first converts the MV-side dc voltage into a high-frequency square-wave voltage applied to the primary of the HFT; the secondary side square-wave signal is then converted to a LV dc waveform by the LV-side converter, which also works as rectifier. Finally, the output LV-side three-phase dc/ac converter, which works as inverter, provides the output power-frequency ac waveform from the LV-side dc link.
Si-based semiconductor technologies can be used for MV applications using a multilelvel configuration. Recently, modular multilevel converter (MMC) topologies have attracted attention for high or medium voltage applications. These converters can provide an effective topology for the MV side of the SST; their main advantages are modularity and scalability: the desired voltage level can be easily achieved by a series connection of MMC sub-modules (SMs). In addition,a MMC topology can provide high power quality and efficiency with reduced size of passive filters. These features made the MMC option an attractive topology for the MV stage of the SST.
This thesis proposes a three-stage SST configuration based on MMC technology for MV converters.
* The input stage of the SST is connected to the distribution system via RL filters and its three-phase configuration uses a MMC technology. A half-bridge configuration is proposed for each SM.
* The isolation stage consists of three parts: a MV single-phase MMC, the high-frequency transformer (HFT), and a single-phase LV PWM converter.
* The LV side of the SST uses a three-phase four-leg PWM converter, with an RL impedance for filtering currents and a capacitor bank for filtering voltages.
The converters and their controller have been implemented adn tested considering models without and with semiconductor losses, while the SST model has been tested as a stand-alone device and a compnent of a distribution system.
The model has been tested under severe dynamic and unbalanced conditions. The simulation results support the choices made for any SST stage and proves that the proposed design could be a feasible choice for the future SST.<br>El Transformador de Estado Sólido ("Solid State Transformer" por sus siglas en inglés) es visto como un reemplazo adecuado del transformador convencional en las futuras redes inteligentes (smart grids ). Este nuevo dispositivo presenta una amplia gama de prestaciones (p.e. mejora de la cualidad de suministro) que pueden ser de crucial importancia para el desarrollo de las redes inteligentes. El principal objetivo de esta tesis es que desarrollar e implantar el en Matlab/Simulink un modelo realista de estado sólido trifásico y bidireccional, que pueda duplicar el comportamiento de un transformador de estado sólido de Media-Baja tensión. El diseño considerado consiste en tres etapas: etapa en media tensión (MT), etapa intermedia, etapa en baja tensión (BT). Cuando la potencia fluye del terminal en media al terminal en baja tensión, la tensión alterna en el terminal de entrada a media tensión y frecuencia de operación 50 Hz se convierte en continua a media tensión mediante un convertidor trifásico rectificador. La etapa intermedia es un puente activo dual, que incluye un transformador de alta frecuencia y los correspondientes convertidores en media y baja tensión: primero, la media tensión continua es convertida en media tensión alterna a alta frecuencia; esta tensión es reducida a baja tensión preservando la alta frecuencia mediante el transformador, finalmente, la tensión en el terminal de salida del transformador es rectificada y convertida en baja tensión continua). La entrada en la etapa de salida en BT es, por tanto, una tensión continua que es convertida en tensión alterna a frecuencia de operación 50 Hz mediante un convertidor que funciona como inversor. Puesto que el diseño del dispositivo estudiado en esta tesis es bidireccional, en caso de que la potencia tenga que fluir desde el lado de BT al lado de MT, la función de los convertidores se invierte (es decir, los rectificadores pasan a operar como inversores, los inversores pasan a operar como rectificadores) en cualquiera de las etapas. Los actuales semiconductores solo pueden ser utilizados en aplicaciones de media y alta tensión empleando convertidores multi-nivel. Durante los últimos años ha ganado popularidad la tecnología MMC (modular multilevel converter), que permite diseñar configuraciones adecuadas para el lado de MT de un transformador de estado sólido; sus principales ventajas están en modularidad y escalabilidad: el nivel de tensión adecuado se puede conseguir mediante la conexión en serie de tantos sub-módulos como sea necesario. Además con la tecnología MMC se puede obtener una alta calidad en las ondas de tensión y corriente, así como un elevado rendimiento con tamaño reducido en los filtros de entrada. Esta tesis propone un diseño trifásico bidireccional con las siguientes características: - La etapa de entrada está conectada a una red de distribución en MT mediante filtros RL y su configuración trifásica usa convertidores de tecnología MMC. - La etapa intermedia contiene tres secciones: un convertidor monofásico en configuración MMC, un transformador de MT/BT y alta frecuencia, y un convertidor monofásico en BT. - La etapa de salida en BT usa un convertidor trifásico PWM (pulse wide modulation), con un filtro RL para las corrientes y un banco de condensadores para filtrar tensiones. Los convertidores han sido implantados en Matlab/Simulink y simulados considerando modelos con y sin pérdidas en los semiconductores, mientras que el modelo completo de transformador de estado sólido ha sido analizado considerando dos configuraciones distintas del sistema a estudiar: el transformador aislado y formando parte de una red de distribución en MT. Los modelos de transformador con y sin pérdidas han sido simulados bajo ciertas condiciones de operación. Los resultados confirman que la configuración seleccionada para cada etapa del nuevo dispositivo permite obtener un diseño fiable que puede mejorar el funcionamiento de las futuras redes inteligentes.
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Hu, Zili. "Development of PHP to UMPL transformer." Thesis, Ball State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3590414.
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<p> This thesis developed a new markup language based on eXtensible Markup Language (XML), named as the Unified Programming Markup Language (UPML), which represents an abstraction of programming techniques of popular programming languages, and is used to store the programming semantic information of various programming languages. UPML aims to provide a general software quality analysis platform and as a gateway to translate programs between high-level programming languages. This research created and analyzed the features of UPML and concluded that UPML may have advantages over the traditional and newly appeared methods in software quality analysis and programming language translation. As the proof of concept in building such a software analysis and translation system, this research developed a PHP to UPML transformer. Execution examples showed its correctness of working in the core programming area of popular programming techniques, structure programming (SP) and object-oriented programming (OOP). The PHP implementation can be easily applied to other programming languages that support the same programming techniques. Since UPML is extensible, languages of other programming paradigms beyond the SP and OOP can be easily added. </p>
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Ayddan, Jonas, and Emin Özbek. "Transformer test bench -implementation and usability." Thesis, KTH, Elektroteknisk teori och konstruktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-170534.
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The task of this master's thesis was to design a transformer test bench while focusing on safety and usability. There are several safety risks when working with high voltages, therefore the high demand for safety precautions. A bench was worked upon, and attachments, such as module frames and banana connectors were integrated into the bench. Further, a list of components were modied and installed on the new bench. A new design, using a magnetic non-contact safety interlock switch and an easy-to-apply circuitry, was proposed and implemented. In addition to the implementation, a code in LabVIEW was written in order to handle the measured data from the tests that can be performed on a transformer. Several tests were performed on a single-phase transformer and a three-phase transformer in order to verify the function of the transformer test bench, with respect to the design. Complications emerged due to random additive noise. After some work, the noise was suppressed and the results showed that the equipment worked well with the new design. Finally, a user's manual was written in order to guide the user through the wire connections, tests and the developed software in LabVIEW.<br>En transformatortestbänk avsedd för laborationer inom forskning och utbildning har utvecklats, där fokus har lagts på säkerhet och användbarhet, eftersom arbete med höga spänningar medför säkerhetsrisker. En bänk modierades för att möjliggöra fastsättning av moduler samt banankontakter. Vidare anskaades elektroniska komponenter, bearbetades och installerades. En design med en magnetisk switch samt lättanvända kretsar föreslogs. Dessutom skrevs en kod i LabVIEW med ett brett användningsområde. Ett flertal tester utfördes på en enfastransformator och en trefastransformator med syfte att säkerställa att komponenter- na fungerar väl ihop med den framtagna transformatortestbänken. En del komplikationer uppstod på grund av slumpmässigt, additivt brus. Detta gick dock att undertrycka. Det slutliga resultatet visade att kom- ponenterna fungerade väl ihop med den framtagna transformatortestbänken. Slutligen skrevs en användarmanual med syfte att instruera använda- re av transformatortestbänken beträande kopplingarna, testerna samt mjukvaran som är skriven i LabVIEW.
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Rivera, Gomez Franco Wilfrido. "Heat transformer technology and steam generation." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360445.
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Cargol, Timothy L. (Timothy Lawrence) 1976. "A non-destructive transformer oil tester." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/81576.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.<br>Includes bibliographical references (leaves 62-63).<br>A new non-destructive test of transformer oil dielectric strength is a promising technique to automate and make more reliable a diagnostic that presently involves intensive manual efforts. This thesis focuses some of the issues that must be understood to bring the test from the laboratory to the field. Emphasis is placed on reliability and safety by exploring any effect the test has on the transformer oil, the mechanical parameters necessary to give optimal reliability, and failsafe electronics.<br>by Timothy L. Cargol.<br>M.Eng.
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Schlicker, Darrell Eugene. "Flow electrification in aged transformer oils." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38844.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.<br>Includes bibliographical references (p. 317-348).<br>by Darrell Eugene Schlicker.<br>M.S.
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Iyengar, Pravin. "Pulsed MOSFET based linear transformer driver." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24217.
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Pulsed power flash radiography is a rapidly growing technology which involves the generation of intense and short bursts of electric pulses to generate high energy X-rays to inspect dense objects. The generation of fast transition, short width, repetitive pulses for effective output requires switching technology which has limitations. From the traditional slow switching gas trigger switches, switching technology has evolved to semiconductors which has led to improved switching characteristics and delivered pulse shapes. One such semiconductor which is of interest in flash radiography is a power MOSFET. Due to superior switching speeds, repetition rates and modularity, MOSFETs are a strong contender in future pulsed power applications. This thesis focuses on the design of a MOSFET based pulsed power system capable of generating 2.2kV, 200A pulses with turn on and turn off times of less than 10ns and 20ns respectively. In order to achieve the target specification, a high speed current source MOSFET gate driver design specific to the application is proposed. Further, an inductive voltage adder system which utilises multiple lower voltage pulse sources driven by MOSFETs and outputs a higher voltage which is the summation of the total number of voltage sources, is designed to be compatible with the proposed gate driver scheme. A compact high power density pulsed power prototype is demonstrated which provides a benchmark for future research into the development of a larger scale system for flash radiography.
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Sharapov, V. M., and K. V. Bazilo. "Piezoelectric transformer with parallel oscillatiry circuit." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39938.
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Piezoelectric transducers are widely used in electroacoustics, hydroacoustics, in ultrasound, medical, measurement technique, in scanning probe nanomicroscopes, piezoengines and in other fields of science and technology. To create transducers with necessary characteristics the technology of additional elements can be used.
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Борисенко, Олексій Андрійович, Алексей Андреевич Борисенко, Oleksii Andriiovych Borysenko, and K. O. Teletov. "Transformer binary codes into binominal ones." Thesis, Видавництво СумДУ, 2004. http://essuir.sumdu.edu.ua/handle/123456789/22972.
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Aslaksen, Jonasson Alexander, and Alfred Wahlforss. "Diagnosis of Dementia using Transformer Models." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279226.
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Dementia is a syndrome of illnesses resulting in cognitive decline, severely impacting the lives of those afflicted as well as their loved ones. The most common form of dementia is Alzheimer's disease, with roughly 10 million new cases each year. In this study we examine different machine learning models and approaches aimed to aid healthcare professionals in early diagnosis of Alzheimer's disease, potentially automating parts of the diagnostic process. We evaluate our models on the Pitt corpus of the Dementia Bank dataset, using 10-fold cross validation. We compare the BERT and RoBERTa transformer models, and find that both models achieve high accuracy, precision, and specificity. The highest accuracy is achieved by RoBERTa, reaching an accuracy of 86.72%, a precision of 90.69% and a specificity of 90.53%. Furthermore, we explore the viability of using automated speech recognition for automatic transcription of audio samples from patient meetings. RoBERTa achieves an accuracy of 83.59% using transcripts generated by Google's automatic speech recognition, suggesting such methods may be viable for automating certain parts of the diagnostic process. In addition to the exploration of transformer models and their viability for dementia diagnostics, this paper provides a market analysis of a potential automated diagnostics tool utilizing transformer models. The analysis is based on a literature study and on two interviews; one with the CEO of a start-up providing automated dementia tests for healthcare professionals, and one with a psychologist researching dementia as well as potential methods of early diagnosis of dementia. With the interviews and literature study as a basis, we use the SWOT framework, and PEST analysis along with Porter's five forces framework to analyse the current market potential for such an automated tool. Despite detecting several obstacles and difficulties prior to market entry, we find significant potential for such a product given the current state of the market.<br>Demens är ett syndrom av sjukdomar som orsakar kognitiv nedsättning och påverkar både de drabbade och deras familjer. Den vanligaste typen av demens ar Alzheimers sjukdom, med cirka 10 miljoner nya fall per ar. I denna studie undersöker vi olika maskininlärningsmodeller och tillvägagångssätt i syfte att underlätta får sjukvårdspersonal att ställa en tidig diagnos, och möjligtvis att även kunna automatisera vissa delar av diagnosprocessen. Vi utvärderar vara modeller på Pittcorpuset i DementiaBank-datasetet och använder 10-delad korsvalidering. Vi jämför två transformer-modeller: BERT och RoBERTa, och finner att bada modeller åstadkommer goda resultat avseende noggrannhet, precision, specificitet och sensitivitet. Den högsta noggrannheten uppnås av RoBERTa, på 86.72%, en precision på 90.69%, och en specificitet på 90.53%. Vidare undersöker vi gångbarheten i att använda automatisk taligenkänning for automatiserad transkribering av ljudinspelningar från patientmoten. RoBERTa uppnår da en noggrannhet på 83.59% när den använder transkriberad text från Googles automatiska taligenkänningstjänst, vilket tyder på att sådana metoder kan vara gångbara for att automatisera vissa delar av den diagnostiska processen. Förutom undersökning av transformermodeller bidrar detta verk även med en marknadsanalys av marknadspotentialen får ett verktyg får automatiserad demensdiagnostik. Analysen baseras på en litteraturstudie och två intervjuer; en med en VD får en start-upp som erbjuder liknande tjänster, och en intervju med en forskare inom demens. Med litteraturstudien och de två intervjuerna som grund analyserar vi marknadspotentialen med tre ramverk: Porters fem krafter, PEST-analys och SWOTanalys. Vi fastslår att det trots flertal hinder och svårigheter får marknadsinträde finns det stor potential och en stor efterfrågan på en sådan produkt.
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Al, lulu Sadi, Lezan Amen, Mohammad Aljichi, and Mats Isaksson Sandberg. "Wireless signal transmission for HV Transformer." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448131.
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Lu, Shu. "Power transformer magnetization under GIC/GMD." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09232008-144706/.
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Alabdrbalreda, Mohammed. "Power transformer modelling for optimal performance." Thesis, Alabdrbalreda, Mohammed (2015) Power transformer modelling for optimal performance. Honours thesis, Murdoch University, 2015. https://researchrepository.murdoch.edu.au/id/eprint/29836/.
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Power transformer efficiency is dependent on various losses. Efficiency is simply a ratio of the power output to power input. Due to losses the efficiency of a power transformer is always less than 100 per cent. Moreover, the transformer’s performance slightly varies under different loads because of load-dependent losses (winding losses). The main objective of this thesis is to find the optimum load which maximises the efficiency and minimises the voltage regulation on a power transformer operated at its rated voltage. The complete equivalent circuit of a power transformer is developed with various losses taken into account such as winding losses, leakage fluxes, core losses, and magnetisation currents. The model parameters are found by carrying out laboratory measurements. Once the complete equivalent circuit is developed, it is used to calculate the efficiency and the voltage regulation under different loading cases. A simulated model on ICAP is also used to validate the experimental results. A sensitivity analysis is also conducted in this project to see the effect of variations in the parameters on the transformer’s performance.
Finally, the design parameters of a power transformer that can be optimized to reduce losses are considered in this project. The design parameters are related to the electrical parameters of the transformer by mathematical models. The effect of those design parameters on the transformer’s performance is supported by some papers related to design optimisation. This involves the evolution of power transformers design throughout history and the research being carried out for loss reduction. Other factors such as cost and operation environment are not taken into account in this project as it is only focused on efficiency optimization.
The key findings of this project can be summarized as follows; the resistive load has the poorest voltage regulation. The capacitive load has the lowest voltage regulation and it is always negative. The transformer’s maximum efficiency is observed at 60 per cent of the rated load. This is proved by laboratory based experiments and ICAPS simulations. The key design parameters that can be optimized to improve the efficiency are the core lamination thickness, material electrical resistivity, and maximum flux density.
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Jansson, Vincent, David Bergman, and Niklas Hermansson. "High Frequency Transformer : Implementation of prototype." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387307.
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Since its invention in 1885 by Otto Bláthy, Miksa Déri and KárolyZipernowsky, transformers have become an important cornerstone of theelectrical infrastructure we have today. They are found mostprominently in any machinery or device that requires a differentlevel of voltage or current than a general grid can supply, such ascomputers, motors or even cars. In the case of this project, thetransformer was originally intended to be connected to a resonatingH-bridge which supplies the primary coil with high frequency voltagepulses to be converted into a higher voltage transferred to arectifier unit. Because of the level of frequency supplied, thetransformer was required to be constructed with a different type ofcore and cable for the winding. When it became clear that the cablecouldn't be supplied in time, the focus shifted towards constructinga prototype instead. The prototype was designed to generate a certainamount of leakage inductance while subjected to a short circuit test.After a couple of attempts, the group managed to construct atransformer whose leakage inductance was well within range of thespecifications. The finished transformer prototype was delivered andthe group had thus successfully constructed what is to be used as atemplate for further transformers of the same type.A special thanks to ScandiNova Systems AB for initiating this projectand giving us the opportunity to participate, and to Per Nilsson, PerBenkowski and Klas Elmqvist for mentoring us along the way.
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Ntwoku, Stephane Ntuomou. "Dynamic transformer protection a novel approach using state estimation." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45879.
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Transformers are very important parts of any electrical network, and their size increase so does their price. Protecting these important devices is a daunting task due to the wide variety of operating conditions. This thesis develops a new protection scheme based on state estimation.The foundation upon which our protection scheme is built is the modeling of the single phase transformer system of equations. The transformer equations are composed of polynomial and differential equations and this system of equations involving the transformer's electrical quantities are modeled into a system of equations such that highest degree of each of the system's equations is quadratic―in a process named Quadratization and then integrated using a technique called Quadratic integration to give a set of algebraic companion equations that can be solved numerically to determine the health of the transformer.
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Li, Xiang. "Mathematical Model for Current Transformer Based On Jiles-Atherton Theory and Saturation Detection Method." UKnowledge, 2016. http://uknowledge.uky.edu/ece_etds/89.
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Current transformer saturation will cause the secondary current distortion. When saturation occurs, the secondary current will not be linearly proportional to the primary current, which may lead to maloperation of protection devices. This thesis researches and tests two detecting methods: Fast Fourier Transform (FFT) and Wavelet Transform based methods. Comparing these two methods, FFT has a better performance in steady state saturation, and Wavelet Transform can determine singularity to provide the moment of distortion.
The Jiles-Atherton (J-A) theory of ferromagnetic hysteresis is one approach used in electromagnetics transient modeling. With decades of development, the J-A model has evolved into different versions. The author summarizes the different models and implements J-A model in both MATLAB and Simulink.
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O'Sullivan, Francis M. (Francis Martin) 1980. "A model for the initiation and propagation of electrical streamers in transformer oil and transformer oil based nanofluids." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40504.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.<br>Includes bibliographical references (p. 305-309).<br>The widespread use of dielectric liquids for high voltage insulation and power apparatus cooling is due to their greater electrical breakdown strength and thermal conductivity than gaseous insulators, while their ability to conform to complex geometries and self-heal means that they are often of more practical use than solid insulators. Transformer oil is a particularly important dielectric liquid. The issues surrounding its electrical breakdown have been the subject of extensive research. Much of this work has focused on the formation of electrical streamers. These are low-density conductive structures that form in regions of oil that are over-stressed by electric fields on the order of 1 x 108 (V/m) or greater. Once a streamer forms it tends to elongate, growing from the point of initiation towards a grounding point. The extent of a streamer's development depends upon the nature of the electrical excitation which caused it. Sustained over-excitation can result in a streamer bridging the oil gap between its point of origin and ground. When this happens an arc will form and electrical breakdown will occur. Streamers can form due to both positive and negative excitations. Positive streamers are considered more dangerous as they form at lower electric field levels and propagate with higher velocities than negative streamers. Historically, the modeling of streamer development has proved to be a very difficult task. Much of this difficulty relates to the identification of the relevant electrodynamic processes involved. In the first section of this thesis a comprehensive analysis of the charge generation mechanisms that could play a role in streamer development is presented.<br>(cont.) The extent of the electrodynamics associated with Fowler-Nordheim charge injection, electric field dependent ionic dissociation (the Onsager Effect) and electric field dependent molecular ionization in electrically stressed transformer oil are assessed and it is shown that molecular ionization, which results in the development of an electric field wave, is the primary mechanism responsible for streamer development. A complete three carrier liquid-phase molecular ionization based streamer model is developed and solved for a positive needle electrode excitation using the COMSOL Multiphysics finite element simulation suite. The modification of the liquid-phase molecular ionization model to account for the two-phase nature of streamer development is described and the performance of both the liquid-phase and gas/liquid two-phase models are compared with experimental results reported in the literature. The second section of this thesis focuses on the insulating characteristics of transformer oil-based nanofluids. These nanofluids, which can be manufactured from a variety of materials, have been shown to possess some unique insulating characteristics. Earlier experimental work has shown that oil-based nanofluids manufactured using conductive nanoparticles have substantially higher positive voltage breakdown levels than that of pure oil. A comprehensive electrodynamic analysis of the processes which take place in electrically stressed transformer oil-based nanofluids is presented, which illustrates how conductive nanoparticles act as electron scavengers in electrically stressed transformer oil-based nanofluids. As part of this analysis, a completely general expression for the charging dynamics of a nanoparticle in transformer oil is developed.<br>(cont.) The solutions for the charging dynamics of a range of nanoparticle materials are presented and the implications these charging dynamics have on the development of streamers in oil-based nanofluid is explained. To confirm the validity of the electrodynamic analysis, the electric field dependent molecular ionization model for streamers in pure oil is modified for use with transformer oil-based nanofluids. This model is solved for nanofluids manufactured using conductive and insulating particles and the results that are presented confirm the paradoxical fact that nanofluids manufactured from conductive nanoparticles have superior positive electrical breakdown performance to that of pure oil. The thesis concludes by exploring the possibility of developing simplified streamer models for both transformer oil and transformer oil-based nanofluids, which are computationally efficient and can be solved quickly meaning that they can be used as practical design tools.<br>by Francis M. O'Sullivan.<br>Ph.D.
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Ribbenfjärd, David. "Electromagnetic transformer modelling including the ferromagnetic core." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13080.
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In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed. In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model. One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements. Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization.<br>QC20100708
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TANTEH, DERICK NJOMBOG, SHAFIQ YOUSEF AL-LIDDAWI, and DANIEL SSEKASIKO. "PROPERTIES OF TRANSFORMER OIL THAT AFFECT EFFICIENCY." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2664.
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Abstract. Transformer explosions caused by dielectric failure account for over 50% of the disasters. The aim of this thesis is to examine, compare and outline the differences, in function, as dielectric insulators, vegetables oil has, with respect to the mineral oil used in high-power transformers. We will first consider the vegetable oil which has less dielectric capabilities than the mineral oil used in power transformers. Later in the experiments, we will focus mainly to examine the breakdown voltage property, as we try to alter some properties of the respective oils used. Considering the fact that vegetable oil has low viscosity, with its chemical compounds constituting less molecular masses compared to mineral oil, we endorse, from our experimental findings, that mineral oil is indeed worthy and reasonable to be used as a dielectric in high power transformers. In this write-up, we have considered eleven transformer oil properties. In the experiment proper, we considered only the acidity, whose concentration in the transformer oil increases with aging if the transformer, moisture, and a ‘suitable’ impurity like NaOH(aq). At first glance, one would be tempted to think, as we were, that since the increase in acid content of the oil deteriorates its dielectric performance, an increase in alkaline content of the transformer oil, would increase its dielectric ability; reversing the acid effect. But as we see in the results from our experiments, this is false. We think that the visible degradation of the insulating property of the oil, with the introduction of NaOH(aq), is because it acts as an impurity to suitable dielectric function. From the experiments, the heating procedures resulted in the production of toxic gases. This indicated the actual loss of chemical structure and significant breakage of chemical bonds. The resulting chemical composition of the oil does not produce the same dielectric properties as the initial oil sample. Also, here has been considerable inconsistency in the addition of NaOH(aq) or HCl(aq) to both oils. We only added HCl(aq), before every measurement, in two of the experiments. The other experiments were either with moisture, or a single addition of 2cm3 of either HCl(aq) or NaOH(aq) before heating; after which several measurements were taken, at specific intervals, as the mixture cools. We did so, in the latter, in which we had only one addition of a 2cm3 chemical, because in real life, given the short time frame of the experiment, the total amount of acid in the oil has a negligible change. So, in a functioning heated transformer, within a short time frame, there is actually deterioration in oil insulation properties
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Phillips, Lyndal, University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Analysis of polychlorinated biphenyls in transformer oils." THESIS_CSTE_SFH_Phillips_L.xml, 2002. http://handle.uws.edu.au:8081/1959.7/766.
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Polychlorinated Biphenyls (PCBs) were seen as a significant engineering advance when first commercially produced in 1929. They were used as insulators and cooling fluids in electrical transformers and capacitors. There are 209 PCB congenors that are chemically and thermally stable with low inflammability and reactivity. However,they are also highly toxic, suspected carcinogens and bioaccumulate in the food chain. Due to these characteristics they are listed by the United Nations as one of the sixteen worlds persistent organic pollutants POPs). By international agreement, undertaken by the UN, the production of PCBs has been banned and gradually their use will be phased out. Several tests and procedures are discussed in some detail in this research.<br>Master of Science (Hons)
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Phillips, Lyndal. "Analysis of polychlorinated biphenyls in transformer oil /." View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20031222.095244/index.html.
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Thesis (M.Sc.) (Hons.) -- University of Western Sydney, 2002.<br>A thesis submitted to the University of Western Sydney in fulfillment of the requirements for admission to the [degree of] Masters of Science (Honours). Bibliography : leaves 156-163.
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Lavery, Grant. "A prototype transformer insulation condition monitoring system." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1999. http://hdl.handle.net/10092/6037.
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A prototype data acquisition and processing system is developed for evaluating the insulation condition of a power transformer winding in real-time. The Transformer Insulation Condition Monitoring System (TICMS) evaluates the insulation condition by calculating the winding transadmittance function. The winding transadmittance function is used to fingerprint the insulation system and provides a means of monitoring its condition. The use of a transfer function for evaluating the insulation condition of a power transformer winding was proposed by Malewski and Poulin in 1988 [6, Chapter 1]. The work described in this thesis extends their work in a number of important areas and makes the following contributions to the state-of-the-art. Firstly, the TICMS is able to calculate the transadmittance function to 3MHz, which is sufficient to detect breakdown between individual turns in an Extra High Voltage (EHV) transformer. This is a key distinguishing feature of this work and is important as faults between individual turns can quickly snowball into a catastrophic failure. Previous attempts have been successful at determining the transadmittance function to around 1.5MHz, which only allows breakdown between discs to be detected in an EHV transformer. Second, the TICMS is able to determine the transadmittance function on-line and in real-time for a fully energised transformer. This is another key distinguishing feature of this work as it allows action to be taken to remove a faulty transformer from service prior to catastrophic failure. Previous attempts have calculated the transadmittance function in an offline situation over a period of minutes using pre-recorded data.
Recent advances in analog-to-digital converter (ADC) technology and the availability of high speed Digital Signal Processors (DSPs) have made it possible to extend the work of Malewski and Poulin as described above. This thesis describes the key design features of the TICMS which provide it with the ability to determine the transadmittance function over a 3MHz bandwidth in real-time. These features include the application of an excitation with tailored spectral characteristics, a novel transducer arrangement that allows the effective dynamic range of the digitizer to be extended and at the same time online measurements to be performed, a first-in-first-out (FIFO) memory arrangement that allows the high speed data acquisition section to easily interlace to the data processing section, and a powerful 32-bit floating point Digital Signal Processor (DSP) that enables the trans admittance function to be determined in real-time. The graphical user interlace to the laboratory prototype is also
presented.
Also described are the signal processing techniques, both applied and developed, that are used by the TICMS to determine the trans admittance function in real-time. These include the deconvolution of the voltage and current channel transducer output signals, a radix-2 decimation-in-time (DIT) fast Fourier transform (FFT) algorithm that transforms the voltage and current channel inputs into the frequency domain simultaneously, the calculation of the transadmittance function magnitude and phase from the recorded transients, and a zooming algorithm that is used to accurately determine pole height.
The transadmittance function of a 7.5kVA 11kV/230V distribution transformer is determined and compared with that obtained by performing a time consuming sweep frequency test. Artificial faults are inserted into a 2nd 7.5kVA 11kV/230V distribution transformer to establish relationships between the location and size of a fault and the corresponding changes in the transadmittance function. Sets of tests are conducted to evaluate the effect of fault size, fault location, the introduction of simulated partial discharges, and single turn faults. The ability of the system to detect single turn faults is a key feature as this allows faults to be detected before they can snowball into catastrophic failures.
The effect of temperature on the location and height of poles in the transadmittance function of a 7.5kVA 11kV/220V distribution transformer is established through the use of the TICMS. On-line testing of an energised transformer is performed to evaluate the effect of supply voltage magnitude, load current magnitude, and the point in the 50Hz AC cycle when the insulation test is initiated. This information allows the system to compare successive transadmittance functions and generate an alarm signal if insulation condition degradation is found to have taken place. This information will allow the system to eventually become a 'black box' that permanently sits beside a transformer continuously evaluating insulation condition.
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Kendall, Haydn G. "Investigation of leakage flux in transformer tanks." Thesis, Cardiff University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329641.
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Heywood, Richard John. "The degradation models of cellulosic transformer insulation." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/2129/.
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DEMENICIS, LUCIENE DA SILVA. "TRANSMISSION LINE TRANSFORMER FOR HIGHSPEED OPTOELECTRONIC DEVICES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5576@1.
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ERICSSON DO BRASIL<br>A utilização de transformadores de impedância banda larga
possibilita o acoplamento de forma eficiente das linhas
convencionais de 50 (ômegas) dos sistemas de alta
freqüência aos
componentes optoeletrônicos de alta velocidade de baixa
impedância, tais como lasers semicondutores (tipicamente
com 3 a 5 (ômegas) de resistência de entrada). Uma das
principais
restrições para a realização de um transformador de
impedância planar para uso em sistemas de comunicações
ópticas é a sua dimensão física. A fim de se obter um
transformador de impedância compacto, de dimensões
compatíveis com às dos dispositivos optoeletrônicos,
foram
analisadas diferentes configurações. Inicialmente foi
analisada a configuração coplanar (CPW) utilizando
substrato de altíssima constante dielétrica. Devido às
limitações encontradas nesta configuração, são propostas,
aqui, duas outras soluções. As duas novas configurações
propostas associam ao substrato bulk convencional de
alumina, filmes de elevada constante dielétrica. Foi
desenvolvida uma técnica para caracterizar a constante
dielétrica e as perdas dos filmes especialmente
fabricados
para este trabalho. As análises teóricas mostraram que as
configurações propostas apresentam desempenho muito
superior ao desempenho das configurações convencionais
CPW. Foi implementado o transformador de impedância
utilizando uma das soluções propostas e seu desempenho
foi
avaliado experimentalmente.<br>Wide-band transmission line impedance transformer enables
efficient coupling of 50 (ômegas) transmission line
circuits to
low impedance high-speed optoelectronic components such as
semiconductor lasers (typically with input resistance of 3
to 5 [ômegas]). The physical dimensions of the planar
transmission line transformer have to be properly chosen
to allow its use in optical communication systems. In
order to design a high performance impedance transformer
with physical dimensions compatible with optoelectronic
components, several possibilities were investigated. A CPW
configuration with very high dielectric
constant bulk substrate has been analyzed. Simulations
have shown some limitations in the performance of this
configuration. Then, two new configurations were
introduced. Both configurations are obtained using high
dielectric constant films and alumina bulk substrate. A
new technique has been developed in order to characterize
the dielectric constant and the losses of the films
specially made for this thesis. Simulations have shown
that the performance of both new configurations is much
better than the conventional CPW configuration
performance. The planar transmission line impedance
transformer has been constructed using a new configuration
and its performance has been experimentally evaluated.
43
Mouayad, Lama. "Monitoring of transformer oil using microdielectric sensors." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/39497.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.<br>Includes bibliographical references.<br>by Lama Mouayad.<br>M.S.
44
Archer, Dale S. "An adaptive thermal module for transformer monitoring." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/11992.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1988.<br>Includes bibliographical references (leaves 132-133).<br>by Dale S. Archer.<br>M.S.
45
Junaydin, Mohamed Murad. "Automatically measuring the losses of a transformer." Thesis, Blekinge Tekniska Högskola, Institutionen för signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12870.
Full textAbstract:
This thesis is an ongoing project of Alstom Power Sweden AB, Växjö with a collaboration of Blekinge Institute of Technology [BTH] to automatically measure the losses of a transformer. So far the company performed the measurements manually to get this loss, and they decided to automatize the measurement process. This paper presents the state space modelling approach of DC-DC Buck converter and simulation of the whole measurement circuit incorporated with the PID controller. The PID controller will control the outputs voltage of the buck converter and the output current of the resonant circuit (secondary current of the transformer) with PI controller and those will be displayed in graph. The switching frequency of the dc-dc converter (buck) is set to 50 kHz. This system is implemented in MATLAB Simulink software.
46
Chiang, Arvin, and 姜義峰. "Current Transformer Saturation Detection Using Wavelet Transform." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/38630066492618497025.
Full textAbstract:
碩士<br>長榮大學<br>經營管理研究所<br>94<br>Digital protection relay for transmission lines utilizes voltage and current samples to discriminate faults in power system. Traditionally, current transformer (CT) is used to scale down the primary current to small secondary current for sampling. When a fault occurs on transmission lines, fault current contains an exponential decaying DC offset. It may cause the core of CT to saturate and result in distorted secondary current. Moreover, it results in a mal-operation in the protection relay. A CT saturation detection method is proposed in this thesis by analyzing the secondary current through Discrete Wavelet Transform (DWT). The level 1 detail coefficients in DWT are used to identify the start and end point when CT saturation occurs. The simulation results by MATLAB/SIMULINK revealed that the proposed method can detect the start and end point of CT saturation accurately.
47
McAlpine, Andrew. "Transformer." 2015. https://scholarworks.umass.edu/englmfa_theses/29.
Full text
48
Huang, Jhao-Bi, and 黃昭弼. "Design of Transformer Terminal Unit for Transformer Management System." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/19054355524002454089.
Full textAbstract:
碩士<br>國立中山大學<br>電機工程學系研究所<br>100<br>With the economic development, the high quality has become a critical issue for service continuous of power companies. To ensure the stable power supply, the asset management of power equipments is applied to prevent the system outage. With voluminous distribution transformers over very wide area, the real time monitoring of temperature has been included in the scope of smart grid. During recent years, the service outage due to transformer overloading has caused customer panic as well as deterioration of service quality.
This thesis develops the Transformer Terminal Unit (TTU) by integration of computer chip for power consumption, DSP and sampling circuit of temperature measurement to achieve the functions of real time monitoring of transformer operation condition. When an abnormal operation condition such as overloading or high oil temperature occurs, the TTU can report the contingency back to the control station via the hybrid communication system so that the distribution system operators can take remedy action to prevent the contingency. The actual loading and temperature of transforms are also measured and collected in this study to develop the relationship of temperature and loading levels. By collecting transformer temperature, the power demand of a transformer can be estimated and the load shedding can then be activated to prevent the problem of overloading when the temperature exceeds the operation constraint.
49
Liu, Chien-Chih, and 劉建志. "The Effects of Harmonics on Current Transformer and Differential Relay for Transformers." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/30803845673790025693.
Full textAbstract:
碩士<br>中原大學<br>電機工程學系<br>87<br>The use of nonlinear devices such as rectifiers ,converters, power supplies and other devices utilizing solid state switching has increased in industry during recent years. The power quality has been deteriorated by these equipments. This deterioration causes the increasing of power loss, resonance problem, insulation deterioration ,and even safety problem of system apparatus.
This thesis aims at analyzing and probing into the influences of harmonics to differential relay. First it probes the operation of CT in frequency domain. Then, it analyzes and compares the mathematic model, which is constructed by using EMTP, and the real test results.
There are many factors to be considered in transformer differential protection designing and exercising. This thesis only analyzes the influential phenomenons of harmonics to differential relay.
The results of this research can provide the valuable references and assist in applying and designing differential relay.
50
Yeh, Yu-Chung, and 葉俞均. "Piezoelectric Ceramics Transformer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/21807343980157655421.
Full textAbstract:
碩士<br>國立中央大學<br>光電科學研究所<br>92<br>Along with the invention of piezoelectric ceramic, there were many other small-sized but highly efficiency-
transformed devices being researched and developed since then.
In order to reduce the volume of power supplies and raise its efficiency simultaneously, researchers use piezoelectric transformers made by piezoelectric ceramic to serve their purpose.
This thesis focuses in the piezoelectricity of piezoelectric ceramic, how to motivate a piezoelectric transformer, and how to use piezoelectric transformers to drive the backlight source.