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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Calculo dos parametros de linhas de transmissão trifasicas atraves das tensões e correntes em seus terminais / Calculation of parameters of thress-phase transmission lines through voltages and currents in their terminals

Lustosa, Leonardo Silva 14 August 2018 (has links)
Orientadores: Jose Pissolato Filho, Sergio Kurokawa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T06:30:33Z (GMT). No. of bitstreams: 1 Lustosa_LeonardoSilva_M.pdf: 1611174 bytes, checksum: 2c164206f95ffdeb84cf75eeff5c9f1b (MD5) Previous issue date: 2009 / Resumo: O objetivo deste trabalho é calcular os parâmetros longitudinais e transversais de linhas de transmissão trifásica a partir das correntes e tensões nas fases das mesmas. Serão utilizadas equações desenvolvidas no domínio modal considerando as obtenções de correntes e tensões em um terminal da linha enquanto o outro terminal permanece em aberto ou em curto-circuito. Inicialmente é apresentada a teoria básica de linhas de transmissão partindo do pressuposto de que tais linhas são melhores representadas através do modelo de parâmetros distribuídos. Assim através da análise de circuitos elétricos e das leis de Kirchhoff são encontradas as equações diferenciais de segunda ordem de tensão e corrente que caracterizam a linha de transmissão. Em seguida é apresentada a metodologia para cálculo dos parâmetros da linha que utiliza a idéia de impedância equivalente de circuito aberto e curto-circuito quando um dos terminais está em aberto e em curto-circuito respectivamente. Utilizando o Toolbox SimPowerSystem do MatLab são simuladas a obtenção das correntes em linhas de transmissão trifásica de 330 kV, 440 kV e 500 kV, todas com comprimento igual a 500 km. De posse de tais correntes são calculados os parâmetros das linhas de transmissão e comparados com seus valores reais, mostrando a viabilidade da metodologia empregada e que o erro obtido com tal metodologia é menor do que o erro entre os parâmetros reais das linhas após construção e seus parâmetros de projeto existente nos bancos de dados das empresas. / Abstract: The objective of this work is to calculate the longitudinal and transversal transmission line parameters using phase currents and voltages. Developed equations are used, in the modal domain, considering current and voltages found between a line terminal and an open line terminal, and a short-circuit terminal. . Initially, the basic transmission line theory is presented assuming that these lines are best represented by distributed parameters model. Therefore, through the analysis of electric circuits and Kirchhoff's laws , second order differential equations for voltage and current are found, which characterizes the line transmission. Next it is shown the method to calculate the line parameters, which uses the concept of open circuit and short-circuit equivalent impedance when one of the terminals is open or in short-circuited respectively. Using the Toolbox of MatLab, SimPowerSystem, estimated currents are simulated in a three-phase transmission line of 330 kV, 440 kV and 500 kV, all with the length of 500 km. The found values are used to calculate parameters of lines transmission and to compared them with their real values, showing that the calculation is possible and that the error obtained with this method is smaller than an error between the real line parameters after construction and those of existing project in the data base of companies. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica
52

Self-damping characteristics of transmission line conductors subjected to free and forced vibration

Mokeretla, Molungoa Samuel 02 1900 (has links)
Thesis (M. Tech.) - Central University of Technology, Free State, 2011 / The objectives of this research were to investigate and establish a procedure to determine the self-damping characteristics of transmission line conductors subjected to free and forced vibrations. The TERN and Aero-Z IEC62219-REV240609 conductor cables were the transmission line conductors that were readily available at the Vibration Research and Testing Centre (VTRC) of the University of KwaZulu-Natal (UKZN). The question to be answered was whether the self-damping characteristics of the TERN and Aero-Z IEC62219-REV240609 conductors were adequate to suppress Aeolian or wake-induced vibrations. In other words, is it necessary for external damping mechanisms to be used with these conductors? This study confirmed that the self-damping characteristics of conductors are not adequate to suppress Aeolian or wake-induced vibrations. Governing partial differential equations describing the characteristics of the catenary and parabolic cable conductors were developed to validate the experimental results. The experimental tests involved both conductors being subjected to an impulse function (a free vibration method) and also to a harmonic function (a forced vibration method). Measurements were carried out using accelerometers, and the recording equipment consisted of oscilloscopes and the PUMA system. With both the free and forced vibration methods, the damping factor of the TERN conductor was confirmed to be ζ ≤ 0.05, whereas the damping factor of the Aero-Z IEC62219-REV240609 was confirmed to be ζ ≤ 0.2. A procedure for determining the self-damping characteristics of the TERN and Aero-Z IEC62219-REV240609 conductors was developed, with the damping factor found to be ζ ≤ 0.2 for both conductors. These methods can assist in the implementation of procedural analysis of the self-damping behaviour of different types of transmission conductors and in finding the most suitable mass absorber (damper) to use in reducing the rate of failure of transmission line conductors. The results of this study can be used to improve the mathematical modelling of Aeolian and wind-induced vibrations where both self-damping properties and a mass absorber are incorporated.
53

SELECTED ASPECTS OF POWER ENGINEERING AS RELATED TO THE WESTERN AREA POWER ADMINISTRATION.

Sundberg, John Raynor. January 1982 (has links)
No description available.
54

HV Transmission line and tower inspection safe-fly zone modelling and metrology

Groch, Matthew 12 1900 (has links)
Thesis (MEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The deployment of Unmanned Aerial Vehicles (UAV) for power line inspection requires the definition of safe-fly zones. Transient Over-Voltages (TOVs) on the Overhead Transmission Lines (OHTLs) put the UAV at risk if it encroaches on these zones. In order to determine the safe-fly zones of a UAV in the vicinity of OHTLs, realistic full-scale experimental tests are done. Non-linearity in breakdown effects renders small-scale testing and computational work inaccurate. Experimental work is used to describe the close-up approach distances for worst-case scenarios. Testing cannot provide a full solution due to the limitation of the equipment available. Further tests must therefore be done at a specialised facility. Experiments are run in two phases, namely non-linear and linear tests in the High Voltage (HV) laboratory. The non-linear tests are done to derive Minimum Approach Distances (MAD). The linear experiments are used to calibrate FEKO, the simulation tool, to the measurement environment. Once correlation between the linear test data and the simulated data is found, confidence is derived in both the simulation model and the test setup. The simulations can then be used to determine a geometric factor as an input into F. Rizk’s prediction equations. The Rizk equations are used to describe the safe-fly zones alongside OHTLs as an addition to the non-linear experimental work. Along with the standard’s suggestions, the Rizk predictions are formulated in such a way that line-specific solutions can be determined. The suggested clearance values are provided in terms of per unit values, which can be selected in accordance with historical line data. Power line sparking is investigated to better understand the line radiation phenomenon. This understanding could assist in the line inspection process, as well as in the layout of power lines near radio quiet areas. Knowledge of OHTL radiation patterns can aid in the location of corona and sparking sources in the inspection process. Aerial sparking measurements are taken using a UAV carrying a spectrum analyser. Measured sparking levels are used to verify a Computational Electromagnetic (CEM) model. The CEM model can then be used to further investigate OHTL radiation characteristics. / AFRIKAANSE OPSOMMING: Die aanwending van Onbemande Vliegtuie (UAVs) vir kraglyn inspeksies, vereis die definiëring van veilige vlieg sones. Oorspannings (TOVs) op oorhoofse kraglyne (OHTLs) kan hierdie vliegtuie in gevaar stel as hulle die grense van hierdie sones oorskry. Om die veilige vlieg sones van 'n UAV in die omgewing van OHTLs te bepaal, is realistiese volskaalse toetse gedoen. Die nie-lineariteit in afbreek effekte lewer onakkurate kleinskaal toetse en rekenaar werk. Eksperimentele werk word gebruik om die benaderde afstande vir die ergste geval te beskryf. Hierdie werk kan nie 'n volledige oplossing gee nie as gevolg van ‘n beperking op huidige toerusting. Dit beteken dat verdere toetse, by ‘n meer gespesialiseerde fasiliteit, gedoen moet word. Eksperimente is uitgevoer in twee fases: nie-lineêre en lineêre toetse in die Hoogspannings (HV) laboratorium. Die nie-lineêre toetse word gedoen om die kleinste-benaderde-afstand (MAD) af te lei en die lineêre eksperimente word gebruik om FEKO (‘n numeriese elektromagnetika simulasie program) met die metings omgewing te kalibreer. Sodra daar ‘n korrelasie tussen die lineêre data en die gesimuleerde data is, kan daar aangeneem word dat die simulasie model en die toets-opstelling betroubaar is. Die simulasies kan dan gebruik word om 'n meetkundige faktor te bepaal as 'n bydrae tot F. Rizk se voorspellings vergelykings. Die Rizk vergelykings word gebruik om die veilige vlieg sones langs die OHTLs te beskryf. Dit kan dus gebruik word as ‘n toevoeging tot die nie-lineêre eksperimentele werk. Saam met die normale meet standaard voorstellings, is die Rizk voorspellings geformuleer sodat dit die lyn spesifieke oplossings kan bepaal. Die voorgestelde verklarings waardes word in per eenheid waardes beskryf, wat dan gekies kan word met ooreenstemmende historiese lyn data. Kraglyn-vonke word ondersoek om die lyn-bestraling verskynsel beter te verstaan. Hierdie begrip kan in die lyn inspeksie proses en in die uitleg van kraglyne naby radiostilte-areas help. Kennis van OHTL bestralings patrone kan help met die identifisering van corona en vonk-bronne tydens die inspeksie proses. 'n UAV met 'n aangehegte spektrum analiseerder is gebruik om die lug-vonkende metings te neem. Vonk vlakke wat gemeet is word dan gebruik om 'n Numeriese Elektromagnetiese (CEM) model te bevestig. Die CEM model kan dan gebruik word om OHTL bestralings eienskappe verder te ondersoek.
55

Modelling risk of Blue Crane (Anthropoides paradiseus) collision with power lines in the Overberg region

Kotoane, Mapule 12 1900 (has links)
Thesis (MA)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This study addresses the problem of Blue Crane (Anthropoides paradiseus) collisions with power lines in the Overberg region, home to approximately 50% of South Africa's national bird's global population. The low visibility of power lines against the landscape is considered to be the major cause of collisions. These claim at least 20 birds annually, which is a considerable loss to a vulnerable species. For this study, expert knowledge of the Blue Cranes' biology, general behaviour and use of its habitat were compiled. These were then translated into rules that were integrated into a Geographic Information System (GIS) to establish a predictive model, which attempts to identify and quantify risk power lines that Blue Cranes are most likely to collide with. The criteria that were considered included landscape proximity of power lines to water bodies arid congregation sites, land cover, power lines orientation in relation to predominant wind directions (North Westerly and South Easterly) and visibility of the power lines against the landscape. The power lines were ranked as highest, high, medium, low and no risk. It is recommended that this classification be used to prioritize the proactive marking of power lines with bird flappers in order to reduce collisions. The results show that 27% of the power lines in the study area pose the highest risk and should therefore be marked immediately. The power lines classified as high (1%), medium (28%) and low risk (21 %) should be marked over short, medium and long term, respectively .. The study demonstrated the potential of GIS in the conservation of Blue Crane. The GIS model developed in this study can be applied in areas of similar habitat such as the Swartland or with some modifications in a slightly different habitat such as the Karoo. It is envisaged that the results of this study will be of great value to the ESKOM (South African Electricity Commission) and Endangered Wildlife Trust (EWT) Partnership and conservation authorities in the effort to save the Blue Crane. / AFRIKAANSE OPSOMMING: Hierdie studie het die probleem van botsings deur Bloukraanvoëls met kraglyne in die Overberg-omgewing van die Wes-Kaap ondersoek. Die Overberg-omgewing huisves ongeveer 50% van Suid Afrikaanse nasionale voël se wêreldbevolking van Bloukraanvoëls, en aangesien kraglyne normaalweg nie maklik sigbaar is teen die landskapsagtergrond nie, verhoog dit, tesame met die biologiese eienskappe van Bloukraanvoëls, die waarskynlikheid dat die voëls met kraglyne sal bots. Hierdie botsings met kraglyne eis minstens 20 Bloukraanvoëls per jaar, wat 'n aansienlike en beduidende aantal vir 'n kritiese bedreigde spesie is. Die studie het gepoog om spesialiskennis oor Bloukraanvoël-biologie, algemene gedrag en habitatgebruik, om te sit in 'n stel reëls, wat in 'n Geografiese Inligtingstelsel (GIS) geïntegreer is om 'n voorspellingsmodel te bou. Hierdie voorspellingsmodel is aangewend om kraglyne wat 'n hoë risiko vir Bloukraanvoëls inhou, te identifiseer en die waarskynlikheid vir botsings te kwantifiseer. Die model aanvaar dat die volgende omgewingsfaktore in die Overberg-omgewing verband hou met die waarskynlikheid van botsings, naamlik: die nabyheid van kraglyne aan waterliggame of gebiede waar voëls saamtrek, die voorkoms van natuurlike veld, die heersende windrigtings (Noordwes en Noordoos) en lae sigbaarheid van kraglyne teen die donker landskapsagtergrond. Die geïdentifiseerde kraglyne is as eerste-, tweede, derde. en vierderangse prioriteit geprioritiseer om as riglyn te dien vir die proaktiewe aanbring van flappers (wat dit ten doel het om voëlbotsings te verminder) deur ESKOM. Die studie het bevind dat 27% van die kraglyne in die Overberg-omgewing eersterang prioriteite is, en dat hierdie kraglyne onmiddellik gemerk sal moet word. Die tweederang prioriteit kraglyne (1%) saloor die mediumtermyn gemerk word, terwyl die derderangse prioriteit kraglyne (28%) oor die langtermyn gemerk sal word. Die vierde prioriteit kraglyne (21 %) kon oor die langertermyn gemerk word. Die studie het die omvang van die probleem, sowel as die rol van GIS in die bewaring van die Bloukraanvoëls beklemtoon. Die GIS-model wat in die studie ontwikkel en gebruik is, kan in soortgelyke gebiede soos die Swartland, of in ietwat verskillende omgewings soos die Karoo getoets word, met die doelom die habitatvoorkeure van Bloukraanvoëls beter te verstaan en navorsers te help om 'n beter begrip van die model te ontwikkel en sodoende die resultate te verbeter. Dit word voorsien dat hierdie studie en verslag baie belangrik sal wees vir die ESKOM-EWT Vennootskap en ander betrokke bewaringsorganisasies in 'n poging om Bloukraanvoël-bewaring aan te help.
56

Modelo reduzido de linhas de transmissão para transitorios eletromagneticos : aplicação de propriedades complexas / Condensed transmission line model to electromagnetic transient phenomena : use of complex properties

Paz, Marcos de Araujo 18 November 2005 (has links)
Orientador: Maria Cristina Dias Tavares / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-07T13:37:43Z (GMT). No. of bitstreams: 1 Paz_MarcosdeAraujo_D.pdf: 6127820 bytes, checksum: 21f6dc485bcf097846769f086c2362ad (MD5) Previous issue date: 2005 / Resumo: O objetivo deste trabalho é contribuir para o estudo de linhas de transmissão e o desenvolvimento de modelos de linhas voltados a programas do tipo EMTP. O trabalho desenvolvido consiste em aproveitar as propriedades e semelhanças dos modos não homopolares de propagação das linhas de transmissão, sejam elas idealmente transpostas ou que apresentem plano de simetria vertical. Por meio de manipulações da matriz de transformação fase-modo-fase através do uso de vetores ortogonais e elementos complexos no domínio modal, pode-se reduzir a dimensão dos vetores de estado. O procedimento proposto é direcionado às modelagens que utilizam transformação fase-modo-fase na determinação das variáveis de estado (corrente e tensão) nas linhas de transmissão. Os recursos usados levam a uma redução tanto em número de operações por iteração quanto em alocação de estados, otimizando o procedimento de cá1culo e aumentando a velocidade de simulação no processamento. A economia computacional que o procedimento proposto proporciona pode ser usada em ferramentas de simulação em tempo real / Abstract: The research objective is to contribute with the study of the transmission line and the development of line models in EMTP-type programs. The proposed model takes advantage of some similarities between non homopolar modes, applying orthogonal vectors and complex number theory to manipulate the state vectors in modal domain reducing the state vectors dimension. The proposed procedure is aimed to the modelling that use phase-mode-phase transformation in the determination of state variables (current and voltage) in transmission lines. The resources used lead to a reduction both in the number of operations per iteration and state allocation, optimizing the procedure and increasing the processing simulation speed. The computational economy, which the proposed procedure provide, can be applied to real-time simulation tools / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

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