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Esta dissertação realiza uma análise comparativa de sobretensões transitórias que ocorrem durante o chaveamento de disjuntores a vácuo. Estas sobretensões podem ocasionar a falha da isolação dos equipamentos conectados aos disjuntores, conforme vários relatos da literatura. Esse fenômeno está associado às características intrínsecas dos disjuntores a vácuo, na formação do arco elétrico em seu interior e de sua interrupção, na sua capacidade de recuperação da rigidez dielétrica, na sua capacidade de interromper correntes de alta frequência, além de características do circuito protegido. Devido à natureza complexa e aleatória das sobretensões transitórias, observou-se a necessidade do desenvolvimento de ferramentas para reprodução dos fenômenos associados às características operacionais dos disjuntores a vácuo. Esse trabalho busca preencher tal lacuna, desenvolvendo um modelo que contempla o comportamento do disjuntor a vácuo tanto para a manobra de abertura quanto para de fechamento, de modo a colaborar com o entendimento dos fenômenos e no cálculo das sobretensões no domínio do tempo. O algoritmo desenvolvido foi implementado no programa Alternative Transient Program (ATP) por meio da linguagem Models. A partir da preparação desse modelo e da escolha de um experimento de referência, foi possível analisar o comportamento do modelo proposto do disjuntor e dos modelos dos principais componentes elétricos dos programas de cálculo de transitórios elétricos, como transformadores e cabos, cujos méritos e deficiências são discutidos ao longo do trabalho. A pesquisa foi orientada em buscar resultados que pudessem ser mais representativos para validação do modelo de disjuntor ao se alterar os modelos dos demais componentes elétricos do circuito, sendo o ajuste dos parâmetros dos disjuntores a vácuo realizados de forma a obter os resultados mais próximos da referência. Por fim, foram simuladas condições onde os fenômenos de sobretensão se agravam e soluções que podem ser incorporadas ao circuito para redução das sobretensões e das frequências dos transitórios. / The current dissertation project performs a comparative analysis of the transient overvoltages generated during the switching of vacuum circuit breakers. The overvoltage phenomenon for these cases can lead to the insulation failure of the equipment connected to the circuit-breakers, according to several reports in the literature. This phenomenon is associated to intrinsic characteristics of the vacuum circuit-breakers, as the formation of the electric arc in their interior and its interruption, their dielectric strength recovery, in their capacity to interrupt high frequency currents interruption, beyond characteristics from the circuit. Due to the complex and random nature of the transient overvoltage, the necessity of developing tools to reproduce such phenomenon associated to the operational features of the vacuum circuit-breaker arose. This dissertation seeks filling this gap, by developing a model that contemplates the vacuum circuitbreaker behavior for both opening and closing switching, in order to collaborate with the understanding of such phenomenon and in the calculations of overvoltages in the time domain. The developed algorithm was implemented in the software Alternative Transient Program (ATP) by means of the programming language Models. From the preparation of this model and from the choice of a reference experiment, it was possible to analyze the behavior of the proposed model and of the models from the main electrical components present in software to calculate electrical transients, e.g. transformers and cables, which merits and deficiencies are discussed along the dissertation. The research was oriented in searching for results that could be more representative to the validation of the circuit-breaker model when changing the models of the remaining electrical components of the circuit, being the parameters adjustment of the vacuum circuit-breakers performed in order to achieve the results closer to the reference. Finally, conditions to aggravate the transitory and the incorporation of solution to reduce the overvoltage and frequencies of the transients were also simulated.

Esta tese buscou investigar uma concepção existencial de Educação Ambiental, tendo como suporte o caminho sustentável. O intuito foi realizar uma crítica, à maneira com a qual o conceito de desenvolvimento sustentável é imposto de forma homogênea e hegemônica na Educação Ambiental. Para tanto, apresentamos o caminho sustentável, constituído a partir do envolvimento ambiental, que por sua vez, é tecido por uma luta pela autossuficiência, por uma conservação ambiental e por justiça social, em uma construção alicerçada com o lugar. Logo, pensar a partir do envolvimento ambiental é compreender que há uma diversidade de experiências humanas a partir da relação de intimidade e de pertencimento que determinadas comunidades originárias possuem com o lugar e com a natureza. Neste trabalho, os saberes e as experiências vividas dos extrativistas da reserva extrativista do Extremo Norte do Tocantins são o que fundamentam o envolvimento ambiental. As perspectivas decolonial, e pós-colonial e a fenomenologia alicerçam teoricamente e epistemicamente as tramas da tese. A fenomenologia é também o método para a consecução da pesquisa, com foco em suas compreensões humanistas, além da técnica da pesquisa-ação existencial e da análise-documental. Como resultados, apresentamos que as relações entre os seres humanos para com seus pares e com a natureza, expostas nas essências do caminho sustentável e existentes na reserva extrativista do Extremo Norte do Tocantins, rompem com o pensamento produzido pela sociedade moderno-colonial que impõe uma única maneira de ser sustentável. Por conseguinte, a partir dos resultados obtidos, destacamos que no cotidiano de comunidades originárias, com as essências do caminho sustentável, aliadas a um diálogo de saberes, é que se fundamenta a Educação Ambiental existencial. / This thesis sought to investigate an existential conception of Environmental Education, having as support the sustainable way. The aim was to make a critique, the way in which the concept of sustainable development is imposed in a homogenous and hegemonic form in Environmental Education. To do so, we present the sustainable way, constituted from environmental involvement, which in turn is woven by a struggle for self-sufficiency, for environmental conservation and for social justice, in a construction based on the place. Therefore, to think of environmental involvement is to understand that there is a diversity of human experiences based on the relationship of intimacy and belonging that certain native communities have with the place and nature. In this work, the knowledge and experiences of the extractivists of the extractive reserve of the extreme North of Tocantins are what underpin environmental involvement. The decolonial, and post-colonial perspectives and phenomenology theoretically and epistemically ground the plot of the thesis. Phenomenology is also the method for the pursuit of research, focusing on its humanistic understandings, beyond the existential research-action technique and document-analysis. As results, we present that the relationships between humans towards their peers and with nature, exposed in the essentials of the sustainable way and existing in the extractive reserve of the extreme North of Tocantins, break with the thought produced by modern-colonial society that imposes a only way to be sustainable. Therefore, from the results obtained, we highlight that in the daily life of native communities, with the essences of the sustainable way, allied to a dialogue of knowledge, is the foundation of existential Environmental Education.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-01T17:53:19Z No. of bitstreams: 1 MarcosCavalcanteFilho.pdf: 3427983 bytes, checksum: 5e82591a0024b1ad3cdc6916f97459c7 (MD5) / Made available in DSpace on 2017-06-01T17:53:19Z (GMT). No. of bitstreams: 1 MarcosCavalcanteFilho.pdf: 3427983 bytes, checksum: 5e82591a0024b1ad3cdc6916f97459c7 (MD5) Previous issue date: 2016-04-18 / The well-being of man, with regard to continued use of electricity, translates to energy distributors in a challenging mission. The face of adversity as weather, vandalism, human error and even robustness of the electrical system itself, great advances have been achieved over the years, especially with the adoption of failure decreased methodologies as well as the emergence of technologies more reliable. To illustrate this current scenario, this paper will address the results of the implementation of the pillar Early Management of Total Productive Management (TPM) to identify the gains in reliability of the continuous supply of electricity, this methodology implemented to protect equipment from power substations. For this, the structure will be observed in the electricity sector, substations and their protective equipment, especially the system protection equipments, and finally the implementation of the Early Management to mitigate the failures of the equipment in order to ensure the continuous supply of energy. / O bem-estar do homem, no que diz respeito ao uso contínuo da energia elétrica, traduz-se para as distribuidoras de energia em uma missão desafiadora. Diante das adversidades como condições climáticas, vandalismo, falha humana e até mesmo robustez do sistema elétrico em si, grandes avanços tem-se conseguido ao longo dos anos, principalmente com a adoção de metodologias de diminuição de falhas, bem como o surgimento de tecnologias mais confiáveis. Para ilustrar esse atual cenário, este trabalho abordará os resultados da aplicação do pilar Controle Inicial da Gestão Produtiva Total (GPT) para identificar os ganhos na confiabilidade do fornecimento contínuo da energia elétrica, metodologia essa implementada aos equipamentos de proteção das subestações de energia. Para isto, será observado a estrutura do setor elétrico, das subestações e dos equipamentos de proteção, em especial os equipamentos de proteção do sistema, e por fim, a implementação do Controle Inicial para mitigação das falhas do equipamento afim de garantir o fornecimento contínuo da energia.

<p>Den här rapporten undersöker möjligheterna att standardisera och modulariseralågspänningsställverken i ABB:s HVDC-stationer. Anläggningarna har idag heltkundanpassade lösningar, vilket tar för lång tid att projektera för att kunna svara mot denökade efterfrågan på HVDC-lösningar.Arbetet baseras på tretton stationer i åtta pågående och avslutade projekt. Dessa skiljer sigtill storlek, lokalisering, ålder, dokumentation och stationstyp.För att kunna erhålla en korrekt men samtidigt överskådlig bild överlågspäninngsställverkets laster, granskades varje stations dokumentation. Informationensammanställdes i en databas, som visade de belastningar som var ständigt återkommande.Arbetet visar att det är möjligt att standardisera valda delar av lågspänningsställverken, docktas ingen hänsyn till vare sig storleks- eller kostnadsökning. Arbetet behandlar de mestfrekvent förekommande brytarstorlekarna för de typiska lasterna.Det standardförslag som tagits fram har anpassats för att täcka de brytarstorlekar somförekommit för de typiska lasterna i stationerna. För strömriktartransformatorerna erbjudstvå varianter av skåp, medan det för övriga laster endast förekommer ett alternativ.En alternativ lösning på problemet skulle kunna vara att ta fram en standard för varjestationstyp. Detta förutsätter dock ett större antal projekt av varje typ än de som tagits medi detta arbete.</p> / <p>This thesis investigates the possibilities to standardize and modularize the low-voltageswitchgear in ABB’s HVDC-stations. The reason for this is that the customized solutionthey use today take too much engineering and production time to meet the expectedincrease of projects.The report is based on thirteen stations in eight different closed or ongoing projects. Theselection was based on the station size, geographical location, commissioning year andstation type.In order to obtain a correct representation of the loads in the low-voltage switchgear, therelevant station documentation was reviewed and compiled in a database. The data wasthen analyzed to determine the most frequently occurring loads and their characteristics.The thesis shows that it’s possible to standardize some components in the low-voltageswitchgear. However, this report doesn’t take into consideration any possible increase oftotal size and cost. It also shows the most frequent sizes of the circuit breakers for each ofthe common loads.The standard proposition for the common loads was developed to cover all the occurringsizes of the circuit breakers in the stations. For the converter transformers coolingequipment there’s two different cubicles to choose from, while the remaining loads islimited to a single alternative.An alternative solution could be to develop a standard for each occurring station type.However, this would require that the data from a larger number of projects, for all stationtypes, are reviewed and compiled.</p>

A vacuum interrupter is a switching device used in vacuum circuit breakers, which are widely employed in medium voltage circuits for interrupting the short-circuit fault currents. The vacuum interrupter is the chamber in which the arc extinction and hence the current interruption takes place. On the occurrence of a fault, the breaker mechanism separates the contacts of the vacuum interrupter. As the contacts separate, an arc is established between the contacts. The arc evolves in the contact space and extinguishes at or near the current zero, thus interrupting the current. The processes of arc ignition, evolution and extinction are very complex. These processes are fundamental to the design and the performance of the vacuum interrupter and hence the circuit breaker. The evolution of the arc predominantly depends on the short-circuit current, the design and metallurgy of the contacts. The evolution of the vacuum arc has been the focal point of considerable research activity. Significant effort has been concentrated to understand the various modes of the arc, the transition between the modes, the arc movement and the dependency on the contact design and finally the effect of the arc evolution on the current interruption performance of the vacuum interrupter. The voltage across the contacts during the arcing, termed as the arc voltage, has been a focal point of several research projects. Research has shown that the arc voltage depends strongly on the mode and the evolution process of the arc. The dependency is observed with respect to the magnitude and the nature of the arc voltage. This dependency has been established through the comparison of the arc voltage trace and the actual arc photographs. The arc voltage is thus an important parameter in understanding the arcing process in the interrupter. Arc voltage could also be utilised to compare the arcing behaviour in vacuum interrupters with different contact geometries and metallurgies. Having understood how the arc voltage depends on the arc modes and how it can be used to analyse the arcing performance of the interrupter, this work aims to establish experimentally the dependency of the arc voltage on fundamental parameters of the short-circuit current and the contact design. The variation of the arc voltage is studied with respect to the magnitude of the short-circuit current. It is seen that the magnitude of the arc voltage is higher, for a higher short-circuit current. This dependency is also reflected in the nature of the arc voltage waveform. The effect of cumulative short- circuit operations has been understood through the study of arc voltage variation with respect to the accumulated arcing time. It has been found that the arc voltage consistently decreases as the accumulated arcing time increases. The effect of the contact diameter on the arc evolution has been studied by comparing the arc voltage variations for contacts of different diameters for the same short-circuit current. It is observed that the variation of arc voltage with respect to the contact diameter depends on the type of contact. In the case of radial magnetic field contacts, it has been observed that the arc voltage is lower for a contact with lower diameter. Whereas in the case of axial magnetic field contacts there is an inverse relation between the contact diameter and the arc voltage. Finally, the effect of the type and distribution of the magnetic field on the arc voltage variation as well as the contact erosion has been studied. In general, the observations show that the arc voltage magnitude for the radial magnetic field geometry is higher than the axial magnetic field geometry. Also, there is a significant difference in the appearance of the arc voltage waveforms for the arcs under the two types of magnetic fields. Finite element simulations and short-circuit evaluations have shown that the axial magnetic field contact system with 90 deg coil orientations yield a more uniform distribution of the flux density and hence lower erosion of the contacts. These results show a clear dependence of the arc voltage on the various above mentioned parameters. Thus the arc voltage could be utilised as a diagnostic parameter during the evaluation of the vacuum interrupter. In the present scenario, significant research is being done to increase the breaking capacity of the interrupters. This calls for optimization of design of the existing contacts and the design of novel contact geometries. The arc voltage would be used as an important diagnostic tool in this process. Also, the utilization of vacuum interrupter in high voltage and extra high voltage circuits is being explored. This application requires increase in the contact gap or series connection of gaps. The arc behaviour in longer gaps and gaps connected in series would be an important research area. Again the arc voltage could be used to study the arc evolution in these specialised conditions. The experiments in this research work have been performed on commercial vacuum interrupters. For a dedicated research on vacuum arcs and vacuum interrupter contacts, development of a vacuum arc research facility has also been attempted as a part of this research work.

M. Tech. Electrical Engineering / Investigates the reasons behind the poor performance of distance relays on series compensated lines. In order to achieve this objective, a case study will be established in a power system software (DigSilent Power Factory). Furthermore, a practical incident that occurred on Eskom's compensated network will be examined. However, prior to investigating the performance of the distance relay on transmission lines, there are some other critical aspects that have to be thoroughly understood. These aspects include amongst others: transmission line modelling ; numeric relay algorithms ; distance protection philosophies ; series compensation phenomena ; analysis of distance relays performance on both compensated and uncompensated lines and the action and influence of the MOV. The study will provide a better understanding regarding the dynamic behaviour of the impedance protection relay under fault conditions on series compensated lines and the behaviour of the MOV during a fault.

In order to sustain transmission grid availability and reliability it is imperative that the condition of vital and costly high voltage equipment is ascertained on a continuous or regular basis. It is necessary to establish the effective diagnostic tools or surveillance devices that can be used to assess equipment condition. Emphasis has been placed on refining well-established and more novel but developing condition assessment techniques. It is important to note that condition assessment of equipment also allows the opportunity to predict failure. Based on a complete and systematic assessment, the failure of defective equipment may be evident or predicted in time, thus preventing a forced outage and loss of valuable 'system minutes'. It has also become necessary to extend the life of existing equipment since most of them are reaching the end of their useful life. Replacement strategies have proven to be ineffective due to financial and resource constraints experienced by utilities. Life extension is the work required to keep equipment operating economically beyond its anticipated life, with optimum availability, efficiency and safety. One of its principal components is condition assessment, with the possibility of predicting remnant life. As a result, refurbishment projects are then raised. Refurbishment by replacement, uprating, modifications or change of design of certain key components to extend the life usually requires a substantial amount of capital to be invested. These projects must be economically justified. This thesis focuses on establishing condition assessment techniques for major power equipment such as power transformers. Assessment techniques for instrument transformers and circuit breakers are included, since these are commonly replaced or modified under refurbishment projects. An experimental investigation was carried out to determine the effectiveness of integrating data of two diagnostic techniques i.e. dissolved gas analysis (on-line) and acoustic detection of partial discharges. It was found that there is a correlation between data obtained from an acoustic detection system and an on-line single gas (Hydrogen) analyser. By integrating the data of both on-line monitoring systems, the diagnostic process is further enhanced. In addition, the location of a fixed discharge source was verified by using an acoustic detection system. Further, the sensitivity of the acoustic technique to partial discharge inception voltage, relative to the established electrical detection technique was determined for the experimental arrangement used. The results obtained indicated that this is an effective technique for the evaluation of activity within a transformer structure. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2004.

The electric grid is important in modern society, so the outages should be few. The transmission grid should have a real high availability, since it transports electrical energy across the country. Then, it is difficult to plan outages for maintenance and installation. This thesis lists twenty surveys about failures of circuit breakers and disconnectors, with data about the cause and the lifetime. It also contains a survey of about forty condition-measuring methods for circuit breakers and disconnectors, mostly applicable to the electric contacts and the mechanical parts. As there is no published method to monitor the electric contacts at voltages around 400 kV, a system with IR sensors has been installed at the nine contacts of six disconnectors. The purpose is to avoid outages for maintenance by estimating the condition of the contacts while the disconnectors are still connected to high voltage. The measured temperatures are collected by radio and regressed against the square of the current, since the best exponent for the current was found to be 2.0. The coefficient of determination $R^2$ is high, greater than 0.9. This gives for each contact a regression coefficient, which can serve as an estimate of the condition of the contact. The higher the coefficient is, the more heat is produced at the contact, which can damage the material. This enables a ranking of the different contacts and shows which the worst ones are. This coefficient can also give a dynamic rating of the disconnector. / Elnätet är viktigt i det moderna samhället, så antalet avbrott bör vara lågt. Särskilt stamnätet bör ha en särskilt hög tillgänglighet, då det transporterar elektrisk energi tvärsöver landet. Då blir det svårt att planera avbrott för underhåll och utbyggnad. Denna avhandling tar upp tjugo studier av fel i brytare och frånskiljare med data om felorsak och livslängd. Den har också en översikt av ett fyrtiotal olika metoder för tillståndsmätningar för brytare och frånskiljare, som huvudsakligen rör de elektriska kontakterna och de mekaniska delarna. Eftersom det inte finns någon beskriven metod för att övervaka elektriska kontakter för spänningar på runt 400 kV, har ett system med IR sensorer installerats på de nio kontakterna på sex frånskiljare. Målet är att minska antalet avbrott för underhåll genom att skatta skicket hos kontakterna, när frånskiljarna fortfarande är kopplade till högspänning. De uppmätta temperaturerna tas emot genom radio och behandlas genom regression mot kvadraten av strömmen, då den bästa exponenten för strömmen visade sig vara 2,0. Förklaringsfaktorn $R^2$ är hög, över 0,9. För varje kontakt ger det en regressionskoefficient, som blir en skattning av kontaktens skick. Ju högre koefficienten är, desto mer värme utvecklas det i kontakten, vilket kan leda till skador på materialet. Kontakternas olika koefficienter ger en rankordning dem och därmed en möjlighet att prioritera vilken frånskiljare som ska underhållas först. Systemet kan också användas för att minska eller öka den tillåtna strömmen baserat på skicket. / <p>QC 20150522</p>

Large scale internet services are increasingly implemented as distributed systems to achieve availability, fault tolerance and scalability. To achieve fault tolerance, microservices need to employ different resilience mechanisms such as automatic retries, rate limiting, circuit breaking amongst others to make the services handle failures gracefully and cause minimum damage to the performance of the overall system. These features are provided by service proxies such as Envoy which is deployed as a sidecar (sidecar proxy is an application design pattern which abstracts certain features, such as inter-service communications, monitoring and security, away from the main architecture to ease the tracking and maintenance of the application as a whole), the service proxies are very new developments and are constantly evolving. Evaluating their presence in a system to see if they add latency to the system and understand the advantages provided is crucial in determining their fit in a large scale system.Using an experimental approach, the services are load tested with and without the sidecar proxies in different configurations to determine if the usage of Envoy added latency and if its advantages overshadow its disadvantages. The Envoy sidecar proxy adds latency to the system; however, the benefits it brings in terms of resilience, make the services perform better when there is a high number of failures in the system. / Storskaliga internettjänster implementeras alltmer som distribuerade system för att uppnå tillgänglighet, feltolerans och skalbarhet. För att uppnå feltolerans måste microservices använda olika typer av resiliens mekanismer som automatisk återförsök, hastighetsbegränsning, kretsbrytning bland annat som tillåter tjänsterna att hantera misslyckanden graciöst och orsaka minimala skador på prestandan hos det övergripande systemet. Dessa funktioner tillhandahålls av service proxies som Envoy. Dessa proxies används som sidovagn (sidvagnproxy är ett applikationsdesignmönster som abstraherar vissa funktioner, såsom kommunikation mellan kommunikationstjänster, övervakning och säkerhet, bort från huvudarkitekturen för att underlätta spårningen och underhåll av ansökan som helhet). Dessa tjänster är väldigt nya och utvecklas ständigt. Att utvärdera deras närvaro i ett system för att se om de lägger till latens för systemet och förstå fördelarna som tillhandahålls är avgörande för att bestämma hur väl de skulle passa i ett storskaligt system. Med hjälp av ett experimentellt tillvägagångssätt testas tjänsterna med och utan sidospårproxys i olika konfigurationer för att avgöra om användningen av Envoy lägger till latens och om dess fördelar överskuggar dess nackdelar. Envoy sidecar proxy ökar latensen i systemet; De fördelar som det ger med avseende på resiliens gör tjänsterna bättre när det finns ett stort antal misslyckanden i systemet.