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Fuse holder damage investigationWacharasindhu, Tongtawee. January 2006 (has links)
Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 29, 2007) Includes bibliographical references.
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Field implementation of a transient voltage measurement facility using HV current transformersSiebrits, F. B.(Francois Bart) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The bandwidth of standard HV measurement devices such as capacitive voltage
transformers is too limited in order to measure wideband phenomena. This thesis is
concerned with the investigation into a non- intrusive HV transient voltage
measurement facility using standard substation HV current transformers (CI's)
configured in a transconductance topology. The sensing, summation and integration
of the CT capacitive earth currents are investigated. This thesis also reports on the
development of a optically isolated link using optical fibre for signal transfer and a
computer based data acquisition system. / AFRIKAANSE OPSOMMING: Standaard hoogspannings (HS) meettoerusting soos kapasitiewe spannmgs
transformators het beperkte bandwydte vir die meet van wyeband verskynsels.
Hierdie tesis handel oor die implementering van 'n HS meetstelsel wat op meinbrekende
wyse oorgangsverskynsels meet deur middel van HS
stroomtransformators wat in 'n transkonduktansie topologie gekonfigureer is. Die
meet, sommasie en integrasie van kapasitoewe grondstrome word ondersoek. Hierdie
tesis doen ook verslag aangaande die ontwikkeling van 'n optiese geisoleerde
koppelvlak wat gebruik word vir seinoordrag en 'n rekenaar gebasseerde data
versamelaar. / pdv201406
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Wireless transformer condition monitoring systemZandberg, Hermanus Andries Jakobus January 2013 (has links)
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 / 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.
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Carregamento e envelhecimento de transformadores elétricos de potência e aspectos prioritários para a manutenção baseada na condição : Loading and aging of electrical power transformers and main aspects to condition-based maintenance / Loading and aging of electrical power transformers and main aspects to condition-based maintenanceCarriel, Lázaro Partamian, 1950- 21 August 2018 (has links)
Orientador: José Pissolato Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T11:22:49Z (GMT). No. of bitstreams: 1
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Previous issue date: 2012 / Resumo: O transformador é o maior ativo, o mais importante e o mais caro do sistema elétrico de potência. Este estudo tem a finalidade de apresentar uma metodologia e um processo de análise do ciclo de vida útil de transformadores de potência baseada na condição, para evitar perda de vida adicional devido ao acréscimo de carga em condição de contingência no sistema. A abordagem foi feita em duas fases e abrangem tanto a metodologia da norma ABNT como a norma do IEEE. Na primeira fase é verificado o comportamento do modelo térmico devido a sobrecargas e, na segunda, a influência das condições do óleo isolante / Abstract: The transformer is the largest, most expensive, most important asset in the electric power system. This study will present a methodology to analyze the useful life of power transformers based on their condition, in order to avoid incremental loss of life caused by overload under contingent operating conditions. The approach has been performed in two phases, following both ABNT and IEEE standards. In the first phase, a thermal model evaluates the effect of overloads on transformers' useful life. In the second phase, the influence of the conditions of the insulating oil is verified / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica
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[pt] SUMARIZAÇÃO AUTOMÁTICA DE MULTIPLAS AVALIAÇÕES UTILIZANDO AJUSTE FINO DE MODELOS DE LINGUAGEM TRANSFORMERS / [en] UNSUPERVISED MULTI-REVIEW SUMMARIZATION USING FINE-TUNED TRANSFORMER LANGUAGE MODELSLUCAS ROBERTO DA SILVA 05 July 2021 (has links)
[pt] Sumarização automática é a tarefa de gerar resumos concisos, corretos e
com consistência factual. A tarefa pode ser aplicada a diversos estilos textuais,
dentre eles notícias, publicações acadêmicas e avaliações de produtos ou
lugares. A presente dissertação aborda a sumarização de múltiplas avaliações.
Esse tipo de aplicação se destaca por sua natureza não supervisionada e
pela necessidade de lidar com a redundância das informações presentes nas
avaliações. Os trabalhos de sumarização automática são avaliados utilizando
a métrica ROUGE, que se baseia na comparação de n-gramas entre o texto
de referência e o resumo gerado. A falta de dados supervisionados motivou a
criação da arquitetura MeanSum, que foi a primeira arquitetura de rede neural
baseada em um modelo não supervisionado para essa tarefa. Ela é baseada
em auto-encoder e foi estendida por outros trabalhos, porém nenhum deles
apresentou os efeitos do uso do mecanismo de atenção e tarefas auxiliares
durante o treinamento do modelo. O presente trabalho é dividido em duas
etapas. A primeira trata de um experimento no qual extensões à arquitetura
do MeanSum foram propostas para acomodar mecanismos de atenção e tarefas
auxiliares de classificação de sentimento. Ainda nessa etapa, explora-se o
uso de dados sintéticos para adaptar modelos supervisionados a tarefas não
supervisionadas. Na segunda etapa, os resultados obtidos anteriormente foram
utilizados para realizar um estudo sobre o uso de ajuste fino (fine-tuning)
de modelos de linguagem Transformers pré-treinados. A utilização desses
modelos mostrou ser uma alternativa promissora para enfrentar a natureza não
supervisionada do problema, apresentando um desempenho de + 4 ROUGE
quando comparado a trabalhos anteriores. / [en] Automatic summarization is the task of generating concise, correct, and
factual summaries. The task can be applied to different textual styles, including
news, academic publications, and product or place reviews. This dissertation
addresses the summary of multiple evaluations. This type of application stands
out for its unsupervised nature and the need to deal with the redundancy of
the information present in the reviews. The automatic summarization works
are evaluated using the ROUGE metric, which is based on the comparison of
n-grans between the reference text and the generated summary. The lack of
supervised data motivated the creation of the MeanSum architecture, which
was the first neural network architecture based on an unsupervised model for
this task. It is based on auto-encoder and has been extended to other works,
but none explored the effects of using the attention mechanism and auxiliary
tasks during training. The present work is divided into two parts: the first deals
with an experiment in which we make extensions to the MeanSum architecture,
adding attention mechanisms and auxiliary sentiment classification tasks. In
the same experiment, we explore synthetic data to adapt supervised models
for unsupervised tasks. In the second part, we used the results previously
obtained to carry out a second study on fine-tuning pre-trained Transformer
language models. The use of these models showed a promising alternative to
the unsupervised nature of the problem, outperforming previous works by +
4 ROUGE.
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Few-Shot Learning for Quality InspectionPalmér, Jesper, Alsalehy, Ahmad January 2023 (has links)
The goal of this project is to find a suitable Few-Shot Learning (FSL) model that can be used in a fault detection system for use in an industrial setting. A dataset of Printed Circuit Board (PCB) images has been created to train different FSL models. This dataset is meant for evaluating FSL models in the specialized setting of fault detection in PCB manufacturing. FSL is a part of deep learning that has seen a large amount of development recently. Few-shot learning allows neural networks to learn on small datasets. In this thesis, various state-of-the-art FSL algorithms are implemented and tested on the custom PCB dataset. Different backbones are used to establish a benchmark for the tested FSL algorithms on three different datasets. Those datasets are ImageNet, PCB Defects, and the created PCB dataset. Our results show that ProtoNets combined with ResNet12 backbone achieved the highest accuracy in two test scenarios. In those tests, the model combination achieved 87.20%and 92.27% in 1-shot and 5-shot test scenarios, respectively. This thesis presents a Few-Shot Anomaly Detection (FSAD) model based on Vision Transformers (ViT). The model is compared to the state-of-the-art FSAD model DevNet on the MVTec-AD dataset. DevNet and ViT are chosen for comparison because they both approach the problem by dividing images into patches. How the models handle the image patches is however very different. The results indicate that ViT Deviation does not obtain as high AUC-ROC and AUC-PR scores as DevNet. This is because of the use of the very deep ViT architecture in the ViT Deviation model. A shallower transformer-based model is believed to be better suited for FSAD. Improvements for ViT Deviation are suggested for future work. The most notable suggested improvement is the use of the FS-CT architecture as a FSAD model because of the high accuracy it achieves in classification. / Målet med detta projekt är att hitta en lämplig Few-Shot Learning(FSL) modell som kan användas i ett feldetekteringssystem för användning i en industriell miljö. Ett dataset av Printed Circuit Board(PCB) bilder har skapats för att träna olika FSL-modeller. Detta datasetär avsedd för att utvärdera FSL-modeller i det specialiserade områdetfeldetektering vid PCB-tillverkning. FSL är en del av djupinlärningsom har utvecklats mycket den senaste tiden. FSL tillåter neuralanätverk att lära sig på små datamängder.I detta examensarbete implementeras och testas olika state-of-theart FSL algoritmer på det anpassade PCB-datasetet. Olika ryggradsmodeller används för att upprätta ett riktmärke för de testade FSL-algoritmernapå tre olika dataset. Dessa dataset är ImageNet[6], PCB Defects[14]och det skapade PCB-datasetet. Våra resultat visar att ProtoNets ikombination med ResNet12-ryggraden uppnådde den högsta noggrannheten i två testscenarier. I dessa tester uppnådde modellkombinationen 87,20% och 92,27% i testscenarier med 1-shot respektive5-shot.Detta examensarbete presenterar en Few-Shot Anomaly Detectionmodell (FSAD) baserad på Vision Transformers (ViT). Modellen jämförs med FSAD-modellen DevNet på MVTec-AD-datasetet. DevNetoch ViT väljs för jämförelse eftersom de båda angriper problemetgenom att dela upp bilder i mindre lappar. Hur modellerna hanterarlapparna är dock väldigt olika. Resultaten indikerar att ViT-Deviationinte får lika hög AUC-ROC och AUC-PR som DevNet. Detta beror påanvändningen av den mycket djupa ViT-arkitekturen i ViT Deviationmodellen. En grundare ViT-baserad modell tros vara bättre lämpadför FSAD. Förbättringar för ViT-Deviation föreslås för framtida arbete.Den mest anmärkningsvärda föreslagna förbättringen är användningen av FS-CT-arkitekturen som en FSAD-modell på grund av de lovande resultaten den uppnår i klassificering.
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On-line Calibration of Instrument Transformers Using Synchrophasor MeasurementsChatterjee, Paroma 04 February 2016 (has links)
The world of power systems is ever changing; ever evolving. One such evolution was the advent of Phasor Measurement Units (PMUs). With the introduction of PMUs in the field, power system monitoring and control changed for the better. Innovative and efficient algorithms that used synchrophasors came to be written. To make these algorithms robust, it became necessary to remove errors that crept into the power system with time and usage. Thus the process of calibration became essential when practical decisions started being made based on PMU measurements.
In the context of this thesis ‘calibration’ is the method used to estimate a correction factor which, when multiplied with the respective measurement, negates the effect of any errors that might have crept into them due to the instrument transformers located at the inputs of a PMU or the PMU device itself. Though this thesis mainly deals with the calibration of instrument transformers, work has been done previously for calibrating other components of a power system. A brief description of those methods have been provided along with a history on instrument transformer calibration.
Three new methodologies for instrument transformer calibration have been discussed in details in this thesis. The first method describes how only voltage transformers can be calibrated by placing optimal number of good quality voltage measurements at strategic locations in the grid, in presence of ratio errors in the instrument transformers and Gaussian errors in the PMUs. The second method provides a way to calibrate all instrument transformers (both current and voltage) in presence of only one good quality voltage measurement located at the end of a tie-line. This method assumes that all the instrument transformers have ratio errors and the PMUs have quantization errors. The third method attains the same objective as the second one, with the additional constraint that the data obtained from the field may be contaminated. Thus, the third method shows how calibration of all the instrument transformers can be done with data that is intermittent and is therefore, the most practical approach (of the three) for instrument transformer calibration. / Master of Science
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Efeitos de cargas não-lineares no dimensionamento de transformadores trifásicos de distribuição / Effects of non-linear in design of three-phase distribution transformersSANTOS, Cairo Rezende dos 30 May 2012 (has links)
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Previous issue date: 2012-05-30 / The intense use of solid state converters that use semiconductor in processing
electric power of electrical and electronic equipment brings great benefits such as lower cost,
greater efficiency and comfort, but also brings disadvantages, because when connected to the
distribution system of electricity produced currents distorted relative to the sinusoidal
waveform.. Thus also cause nonsinusoidal voltages that produce additional losses in
conductors, transformers and also in its own equipment that generated them. In transformers
feeding nonlinear loads occur further losses, which increase the temperature and
compromising the insulation life. The factors used and internationally recommended in UL
1561-1994 (K-factor) and IEEE Std C57.110-2008 (Harmonic Loss Factor - FHL) to calculate
maximum power three-phase transformers operating in these conditions will be objects of
comparison. This work, performed in the laboratory with two three-phase transformers
connected in the configuration back-to-back, aims to conduct a survey of actual losses in
transformers under linear and nonlinear load and also propose a new scale factor that the
three-phase transformers feeding these specific charges. Another aspect to be addressed is
planning the design of transformers using these factors. The measurements and data
processing are performed at low voltages of the transformers and use transducers voltage and
current with high accuracy and LabVIEW programming. / O uso intenso de conversores que utilizam semicondutores no processamento da
energia elétrica dentro dos equipamentos elétricos e eletrônicos traz grandes benefícios como
menor custo, maior eficiência e mais conforto, contudo traz também desvantagens, pois,
quando conectados ao sistema de distribuição de energia elétrica produzem correntes
distorcidas em relação à forma de onda senoidal. Desta forma, causam também deformações
na forma de onda das tensões. Estes efeitos produzem perdas adicionais em condutores,
transformadores e também nos próprios equipamentos que as gerou. Em transformadores,
quando do suprimento de cargas não-lineares, ocorrem perdas adicionais, que elevam a
temperatura comprometendo a isolação e a sua vida útil. Os fatores usados internacionalmente
e recomendados na UL 1561-1994 (Fator K) e na IEEE Std C57.110-2008 (Fator de Perda
Harmônica - FHL) para cálculo da potência máxima em transformadores trifásicos operando
nestas condições serão objetos de comparação. Este trabalho, realizado em laboratório com
dois transformadores trifásicos conectados na configuração back-to-back, tem por objetivo
realizar um levantamento real das perdas em transformadores submetidos às cargas lineares e
não-lineares e também propor um novo fator que dimensione os transformadores trifásicos
alimentando estas cargas específicas. Outro aspecto que será abordado é o planejamento do
dimensionamento de transformadores utilizando-se destes fatores. As medições e tratamento
de dados são realizados nas tensões inferiores dos transformadores que utilizam transdutores
de tensão e de corrente de alta precisão e programação em LabVIEW.
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Transformer-Based Multi-scale Technical Reports Analyser for Science Projects Cost Prediction / Transformers-baserad analysator av tekniska rapporter i flera skalor för prognostisering av kostnader för vetenskapsprojektBouquet, Thomas January 2023 (has links)
Intrinsic value prediction is a Natural Language Processing (NLP) problem consisting in determining a numerical value contained implicitly and non-trivially in a text. In this project, we introduce the SWORDSMAN model (Sentence and Word-level Oracle for Research Documents by Semantic Multi-scale ANalysis), a deep neural network architecture based on transformers whose goal is to predict the cost of research projects from the analysis of their abstract. SWORDSMAN is built on a hybrid structure based on two branches in order to conduct a multi-scale analysis by combining the strengths of global and local perspectives to extract more relevant information from these texts. The local branch uses Convolution Neural Networks (CNNs) to analyse abstracts at fine-grained word level and bring more nuance to the understanding of the context of occurrence of key terms, while the global branch combines Sentence Transformers and Radial Basis Functions (RBFs) to process these abstracts at a higher level to identify the overall context of the project, while being more focused on the content than the form of the data. The joint use of these models allows SWORDSMAN to have a better capacity to understand complex data by using this analysis at different levels of granularity to present a better estimation accuracy. / Förutsägelse av inneboende värde är ett problem inom Natural Language Processing (NLP) som består i att bestämma ett numeriskt värde som finns implicit och icke-trivialt i en text. I det här projektet introducerar vi SWORDSMAN-modellen (Sentence and Word-level Oracle for Research Documents by Semantic Multi-scale ANalysis), en djup neuronal nätverksarkitektur baserad på transformatorer vars mål är att förutsäga kostnaden för forskningsprojekt utifrån analysen av deras abstrakt. SWORDSMAN bygger på en hybridstruktur baserad på två grenar för att genomföra en analys i flera skalor genom att kombinera styrkorna hos globala och lokala perspektiv för att extrahera mer relevant information från dessa texter. I den lokala grenen används CNN-nätverk (Convolution Neural Networks) för att analysera sammanfattningar på finkornig ordnivå och ge mer nyans till förståelsen av sammanhanget för förekomsten av nyckeltermer, medan den globala grenen kombinerar meningstransformatorer och radiella basfunktioner (RBF) för att bearbeta dessa sammanfattningar på en högre nivå för att identifiera projektets övergripande sammanhang, samtidigt som den är mer inriktad på innehållet än på formen av uppgifterna. Den gemensamma användningen av dessa modeller gör det möjligt för SWORDSMAN att ha en bättre förmåga att förstå komplexa data genom att använda denna analys på olika granularitetsnivåer för att presentera en bättre skattningsnoggrannhet. / La prédiction de valeur intrinsèque est un problème de Traitement Automatique du Langage (TAL) consistant à déterminer une valeur numérique contenue de manière implicite et non triviale dans un texte. Dans ce projet, nous introduisons le modèle SWORDSMAN (Sentence and Word-level Oracle for Research Documents by Semantic Multi-scale ANalysis), une architecture de réseaux de neurones profonde basée sur les transformers dont le but est de prédire le coût de projets de recherche à partir de l’analyse de leur abstract. SWORDSMAN est bâti sur une structure hybride reposant sur deux branches afin de mener une analyse multi-échelles en combinant les forces de perspectives globale et locale pour extraire des informations plus pertinentes de ces textes. La branche locale utilise des réseaux de neurones de convolution (CNN) pour analyser les abstracts à l’échelle des mots et apporter plus de nuance à la compréhension du contexte d’apparition des termes clés, là où la branche globale combine Sentence Transformers et fonctions de base radiale (RBF) pour traiter ces abstracts à un plus haut niveau afin d’identifier le contexte général du projet, tout en étant plus focalisée sur le contenu que la forme des données. L’utilisation conjointe de ces modèles permet à SWORDSMAN de disposer d’une meilleure capacité de compréhension de données complexes en se servant de cette analyse à différents niveaux de granularité pour présenter une meilleure précision d’estimation.
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Power Electronic Control of a Partial Core TransformerBendre, Vijay January 2010 (has links)
The research programme at the University of Canterbury includes the development and applications of partial core inductors and transformers for high voltage testing of
generator insulation. Unlike a conventional full core transformer, a partial core transformer has no limbs and yokes. A partial core transformer is a compromise
between a full core and coreless transformer. It is superior to its full core counterpart as far as cost, weight and ease of transportation are concerned.
Partial core transformers have a low magnetising reactance and hence draw a high magnetising current. This characteristic makes them a perfect fit in applications
where the load is capacitive in nature, such as a.c. power frequency high voltage testing of generator insulation and cable testing etc.
The work carried out for this thesis focuses on automatically controlling the amount of reactive power on the supply side of a partial core transformer. The considered design includes a third winding around the existing two windings. A power electronic controller is connected to the third winding, which modifies the VAr
absorption characteristics of the magnetically coupled supply winding.
Two options are considered to achieve continuous reactive power control in the partial core transformer as explained below.
First, a thyristor controlled reactor (TCR) is proposed as the VAr controller. It is modelled using PSCAD/EMTDC software. Simulations reveal the design criteria,
overall performance and the limitations of the suggested proposal. The TCR connected tertiary winding takes the capacitive burden of the supply. The model demonstrates the ability of the automatically controlled TCR to provide a continuous variation of reactive power without significant under or over compensation. This feature limits the supply current to its real component only, so the supply provides
only the losses of the system.
Second, a voltage source converter is considered as the VAr controller. This is modelled in PSCAD/EMTDC and a hardware prototype is designed and built. Based on the analysis, the control algorithm (including a digital PI controller) is implemented using an 8 bit micro-controller, PIC18LF4680. The prototype is tested in the laboratory for both active and inductive load conditions as seen from the
supply side. Performance of the hardware prototype is discussed in detail.
The PSCAD/EMTDC model and the hardware prototype successfully demonstrate the feasibility of a STATCOM controlled partial core transformer. The proposed
system is capable of compensating a wide range of capacitive loads as compared with its TCR counterpart.
It is proved that the system is very robust and remains dynamically stable for a large system disturbance such as change in load from full capacitive to inductive and vice
versa. This confirms that the system is capable of providing continuous VAr control.
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