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Thesis (D. Tech. Electrical engineering) --Vaal University of Technology / A comprehensive study upon "Non-conventional methods for energy extraction from the high voltage transmission lines" was addressed in this thesis. As defined in this study, a non-conventional method to extract energy is one that does not touch the conductors of the line. The theoretical framework which originated in the Maxwell's equations was presented as a base for discussion of all the methods and the conditions for the extraction to be possible. This study presents various methods such as capacitive and inductive to extract energy from high voltage alternating current transmission lines (HVAC). Although in theory, for high voltage direct current transmission lines (HVDC), the conditions for extraction are not matched, there remain some methods that could still attract interest. The centre point of this thesis is the new power application of the Rogowski coil. This method is analysed in full extent starting from theoretical modelling, computer simulations, design of the actual Rogowski coil and power electronics associated with it, and experimental results on a reduced scale model. In doing this, strong mathematical tools and computer software such as Matlab 6, Quick Field and MathCAD were used. At the end of this thesis, some conclusions are presented together with new ideas for further research in the field.

Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη της λειτουργίας των καθοδικών αλεξικεραύνων κατά την προστασία γραμμών μεταφοράς υψηλής τάσης. Ειδικότερα, λόγω της ιδιαίτερης φύσης των κεραυνών και των πληγμάτων που αυτοί επιφέρουν, γίνεται μελέτη μοντέλων που έχουν προταθεί για την προσομείωση των αλεξικεραύνων κατά την λειτουργία τους. / The purpose of this paper is to study the function of surge arresters protecting high voltage transmission lines. Specifically, given the particular nature of lightning strikes and the blows they bring, models that have been proposed for the simulation of surge arrestes during operation are being studied.

Στην παρούσα διπλωματική εργασία μελετάται η ικανότητα συμπεριφοράς γραμμών μεταφοράς υψηλής τάσης έναντι κεραυνών. Αρχικά γίνεται μια ιστορική αναδρομή για τον κεραυνό. Στη συνέχεια, εξετάζονται οι κεραυνοί και παρατίθενται μια ενδελεχής παρουσίαση των ειδών των κεραυνικών αλλά και των ατμοσφαιρικών εκκενώσεων, προχωρώντας μετά στην αναφορά των κύριων χαρακτηριστικών των κεραυνών, των αποτελεσμάτων τα οποία προκαλούν, αλλά και των παραμέτρων από τις οποίες εξαρτώνται και χαρακτηρίζονται. Έπειτα, γίνεται μια αναλυτική περιγραφή των γραμμών μεταφοράς, παρουσιάζοντας τις κατηγοριοποιήσεις στις οποίες υπόκεινται, με κύρια κριτήρια αυτών να είναι η ονομαστική τάση υπό την οποία είναι φορτισμένες, το μήκος αλλά και την ικανότητα τους στην μεταφορά ηλεκτρικής ενέργειας. Επίσης, γίνεται αναφορά στις καταπονήσεις τις οποίες δέχονται οι γραμμές αλλά και στην μόνωση, όπως και στα χαρακτηριστικά τους. Παρακάτω, βλέπουμε ποια είναι τα κύρια είδη σφαλμάτων στις εναέριες γραμμές μεταφοράς και από ποιες αιτίες αυτά προκαλούνται. Το επόμενο κεφάλαιο πραγματεύεται τη μόνωση των γραμμών αλλά και τα κεραυνικά πλήγματα, ενώ εξετάζονται οι μηχανισμοί που προκαλούν την παραγωγή υπερτάσεων στις γραμμές. Έπειτα, για το καθορισμό της θέσης του αγωγού προστασίας της γραμμής παρουσιάζονται οι μέθοδοι της μέγιστης γωνίας και η ηλεκτρογεωμετρική μέθοδος. Στο προτελευταίο κεφάλαιο , υπάρχει μια εκτενής αναφορά στο πρόγραμμα ATP-EMTP και τα στοιχεία του. Τέλος, παρουσιάζεται μια εξομοίωση μιας γραμμής μεταφοράς υψηλής τάσης με τη χρήση του συγκεκριμένου προγράμματος και κυρίως του γραφικού προεπεξεργαστή του , που είναι το πρόγραμμα ATPDraw. Η εξομοίωση αυτή έγινε για διαφορετικών εντάσεων κεραυνικά ρεύματα τα οποία πλήττουν τον αγωγό προστασίας της γραμμής, και μελετά τις παραγόμενες υπερτάσεις σε τέσσερα διαφορετικά σημεία αυτής και το βαθμό επικινδυνότητάς τους. / In this diploma thesis is studied the ability to conduct high voltage transmission lines against lightning. Initially, there is a little historical background to the lightning. Afterwards there is a study about lightning and it is provided a thorough presentation of the types of lightning and atmospheric discharges, moving afterwards to the reference of the main lightning features, the results that they rise, as well as the parameters that they depend on and described from. Next, a more detailed description of the transmission lines, showing the classifications in which they are subject to, with main criteria, the nominal voltage in which they are charged, the length, but also their ability of electricity transmission. Moreover, there is a reference to the stresses, in which the lines are subjected to, as well as their insulation level and their characteristics. Below, we can see what the main types of outages in air transmission lines are and which are the causes that generate them. The next chapter deals with the isolation of lines, as well as with lightning strokes and described the mechanisms which cause the overvoltages on transmission lines. Then, in order to determine the position of the line protection conductor , the maximum angle method as well as the electrogeometrical method are presented. The fifth chapter contains an extended reference to the ATP-EMTP program and its components. Finally, a simulation of a high voltage transmission line is represented, with the use of this program and mainly its graphic preprocessor, which is the program ATPDraw. This simulation has been done for different intensities of lightning currents, which strike at the protection conductor of the line,and it is also studying overvoltages at four different points and the risk rate.

O Brasil é um país de dimensões continentais, onde existe uma considerável distância entre a geração e os principais centros de consumo. Dessa forma, o estudo e desenvolvimento de novas tecnologias de transmissão a longas distâncias é de fundamental importância para o desenvolvimento do país. A solução mais utilizada atualmente é a transmissão em corrente alternada. Entretanto a transmissão em corrente continua também é uma solução viável para longas distâncias. O sistema brasileiro é composto principalmente por linhas 500 kV em corrente alternada (também há 230; 345; 440 e 750 kV), bem como em corrente continua (em ±600 e ±800 kV). O presente estudo apresenta uma solução de transmissão em corrente alternada por linhas de 1000 kV, que se mostrou mais econômico na transmissão de potências superiores a 3.500 MW e distâncias de 1400km. Nos próximos anos, a geração de energia elétrica no Brasil será expandida de forma significativa, ocorrerá um aumento principalmente na geração de energia eólica e solar, localizadas em sua maioria na região Nordeste do país. Esse aumento na geração exigirá a transmissão de grandes blocos de energia elétrica por distâncias significativas, devido à falta de proximidade entre a geração e os principais centros consumidores, que estão localizados no Sudeste. Neste estudo, serão mostradas as etapas de definição de condutor economicamente mais adequado e projeto da geometria da torre. Com base nos dados obtidos, será feita a avaliação do desempenho da linha 1000 kV, durante a operação normal de fluxo de carga, curtos-circuitos e estabilidade. / Brazil, a country of continental proportions, have significant distance between the power generation centers and the main consumer centers. In such way, the study and development of new transmission technologies over long distances is of fundamental importance for the development of the country. Nowadays, the most commonly used solution is alternating current transmission. However, direct current transmission is also a viable solution for long distances. The Brazilian system mainly consists of 500 kV alternating current lines (along with 230, 345, 440 and 750 kV) and direct current lines (± 600 and ± 800 kV). This study provides a solution for transmission in alternating current by lines of 1000 kV, which proved to be more economical in power transmission over 3,500 MW and distances beyond 1400km. In the coming years, the electric power generation in Brazil will expand significantly; a boost will take place mainly in wind and solar power generation, located mostly in the Northeast of the country. This generation expansion will require transmission of large blocks of electric power over considerable distances, due to the lack of proximity between generation sites and main consumer centers located in the Southeast. This study will show the setting stages of the most economically applicable conductor and tower geometry design. Based on the data obtained, the performance of the 1000 kV line will be evaluated during the regular load flow operation, short circuits and stability.

O Brasil é um país de dimensões continentais, onde existe uma considerável distância entre a geração e os principais centros de consumo. Dessa forma, o estudo e desenvolvimento de novas tecnologias de transmissão a longas distâncias é de fundamental importância para o desenvolvimento do país. A solução mais utilizada atualmente é a transmissão em corrente alternada. Entretanto a transmissão em corrente continua também é uma solução viável para longas distâncias. O sistema brasileiro é composto principalmente por linhas 500 kV em corrente alternada (também há 230; 345; 440 e 750 kV), bem como em corrente continua (em ±600 e ±800 kV). O presente estudo apresenta uma solução de transmissão em corrente alternada por linhas de 1000 kV, que se mostrou mais econômico na transmissão de potências superiores a 3.500 MW e distâncias de 1400km. Nos próximos anos, a geração de energia elétrica no Brasil será expandida de forma significativa, ocorrerá um aumento principalmente na geração de energia eólica e solar, localizadas em sua maioria na região Nordeste do país. Esse aumento na geração exigirá a transmissão de grandes blocos de energia elétrica por distâncias significativas, devido à falta de proximidade entre a geração e os principais centros consumidores, que estão localizados no Sudeste. Neste estudo, serão mostradas as etapas de definição de condutor economicamente mais adequado e projeto da geometria da torre. Com base nos dados obtidos, será feita a avaliação do desempenho da linha 1000 kV, durante a operação normal de fluxo de carga, curtos-circuitos e estabilidade. / Brazil, a country of continental proportions, have significant distance between the power generation centers and the main consumer centers. In such way, the study and development of new transmission technologies over long distances is of fundamental importance for the development of the country. Nowadays, the most commonly used solution is alternating current transmission. However, direct current transmission is also a viable solution for long distances. The Brazilian system mainly consists of 500 kV alternating current lines (along with 230, 345, 440 and 750 kV) and direct current lines (± 600 and ± 800 kV). This study provides a solution for transmission in alternating current by lines of 1000 kV, which proved to be more economical in power transmission over 3,500 MW and distances beyond 1400km. In the coming years, the electric power generation in Brazil will expand significantly; a boost will take place mainly in wind and solar power generation, located mostly in the Northeast of the country. This generation expansion will require transmission of large blocks of electric power over considerable distances, due to the lack of proximity between generation sites and main consumer centers located in the Southeast. This study will show the setting stages of the most economically applicable conductor and tower geometry design. Based on the data obtained, the performance of the 1000 kV line will be evaluated during the regular load flow operation, short circuits and stability.

Thesis (D. Tech. Engineering : Electrical ; Dept. Applied Electronics and Electronic Communications) -- Vaal University of Technology / Two methods to convert an AC current source to an AC voltage source are presented. Both methods make use of a current transformer to provide energy extraction from the main system while maintaining galvanic isolation between the main system and the output system. Control is via a pulse width modulation scheme in both instances. The ftrst method uses a storage element to provide a DC voltage, which feeds an inverter that supplies the AC load with a voltage source. The second method does not use a storage element but is a direct AC current source to AC voltage source converter employing a current transformer. This has not been done before. A possible application of this study is in the extraction of power from high voltage transmission lines without the conventional substation and rural grid to supply small users such as the telecommunication industry.

Les phénomènes de couplage électromagnétique entre les lignes aé- riennes de transmission d\'énergie et des structures voisines sont inévitables, surtout dans les zones densément peuplées. Les effets indésirables découlants de cette proximité sont variés, allant de l\'établissement des tensions dangereuses à l\'apparition de phénomènes de corrosion dus au courant alternatif. L\'étude de cette classe de problèmes est nécessaire pour assurer la sécurité dans les alentours de la zone d\'interaction et aussi pour préserver l\'intégrité des équipements et des dispositifs présents. Cependant, la modélisation compl ète de ce type d\'application implique la représentation tridimensionnelle de la région d\'intérêt et nécessite des méthodes numériques de calcul de champs spécifiques. Dans ces travaux, des problèmes liés à la circulation de courants électriques dans le sol (ou de couplage dit conductif) seront abordés avec la méthode des éléments finis. D\'autres problèmes résultants de la variation temporelle des champs électromagnétiques (ou de couplage dit inductif) seront aussi considérés et traités avec la méthode PEEC (Partial Element Equivalent Circuit) généralisée. Plus précisément, une condition limite particulière sur le potentiel électrique est proposée pour tronquer le domaine de calcul dans l\'analyse par éléments finis des problèmes de couplage conductif et une formulation PEEC complète pour la modélisation de problèmes de couplage inductif est présentée. Des con gurations tests de complexités croissantes sont considérées pour valider les approches précédentes. Ces travaux visent ainsi à apporter une contribution à la modélisation de cette classe de problèmes, qui tendent à devenir communs avec l\'expansion des réseaux électriques. / Electromagnetic coupling phenomena between overhead power transmission lines and other nearby structures are inevitable, especially in densely populated areas. The undesired effects resulting from this proximity are manifold and range from the establishment of hazardous potentials to the outbreak of alternate current corrosion phenomena. The study of this class of problems is necessary for ensuring security in the vicinities of the interaction zone and also to preserve the integrity of the equipment and of the devices there present. However, the complete modeling of this type of application requires the three- -dimensional representation of the region of interest and needs specific numerical methods for field computation. In this work, the modeling of problems arising from the flow of electrical currents in the ground (the so-called conductive coupling) will be addressed with the finite element method. Those resulting from the time variation of the electromagnetic fields (the so-called inductive coupling) will be considered as well, and they will be treated with the generalized PEEC (Partial Element Equivalent Circuit) method. More specifically, a special boundary condition on the electric potential is proposed for truncating the computational domain in the finite element analysis of conductive coupling problems, and a complete PEEC formulation for modeling inductive coupling problems is presented. Test configurations of increasing complexities are considered for validating the foregoing approaches. These works aim to provide a contribution to the modeling of this class of problems, which tend to become common with the expansion of power grids.

The dissertation comprises the general characteristic of the work, 5 chapters, conclusions and recommendations, references and list of published works on the topic of the dissertation. The dissertation covers 149 pages, 78 illustrations, 17 tables. In introduction chapter the problem topicality is considered, the aims and tasks of the work are formulated, the novelty of the research is described, the author’s reports and publications as well as the dissertation structure are presented. Chapter 1 is intended for the review of literature. The survey of ozone sources in working premises and the environment air is presented as well as methods of the ozone concentration determination and its dispersion simulation are discussed. At the end of the chapter conclusions are formulated and the dissertation tasks are concretized. In chapter 2 the methodology of the ozone concentration determination with the ozone analyzer and passive samplers as well as the measurement methods of aerosol particles and meteorological, microclimatic parameters are described. In chapter 3 the results obtained during experimental investigations are discussed: the ozone concentration changes near technogenic sources of this pollutant, the influence of meteorological and microclimatic parameters on the ozone concentrations changes, the relation of aerosol particles with the ozone concentration. Ozone concentrations measured by different methods are compared and the results of comparative measurements are... [to full text] / Disertaciją sudaro įvadas, 5 pagrindiniai skyriai, darbo išvados ir rekomendacijos, literatūros sąrašas, publikacijų sąrašas. Bendra disertacijos apimtis – 149 puslapiai, 80 iliustracijų, 17 lentelių. Įvadiniame skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pristatomi autoriaus pranešimai ir publikacijos, disertacijos struktūra. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta ozono šaltinių darbo patalpose ir aplinkos ore apžvalga, aptariami ozono koncentracijos nustatymo ir jos sklaidos modeliavimo metodai. Skyriaus pabaigoje formuluojamos išvados ir konkretinami disertacijos uždaviniai. Antrajame skyriuje aprašomi ozono koncentracijos nustatymo ozono analizatoriumi ir pasyviaisiais kaupikliais metodika bei aerozolio dalelių ir meteorologinių, mikroklimato parametrų matavimo metodai. Trečiajame skyriuje aptariami eksperimentinių tyrimų metu gauti rezultatai apie: ozono koncentracijos kitimą prie technogeninių šio teršalo šaltinių, meteorologinių ir mikroklimato parametrų įtaką ozono koncentracijos pokyčiams, aerozolio dalelių sąryšį su ozono koncentracija. Lyginamos ozono koncentracijos matuotos skirtingais metodais ir aptariami lyginamųjų matavimų rezultatai. Ketvirtajame skyriuje pateikti RISK programa sumodeliuoti ozono sklaidos nuo šaltinio rezultatai. Penktajame skyriuje pasiūlytas technologinis sprendimo variantas, leidžiantis sumažinti ozono koncentracijas prie technogeninių... [toliau žr. visą tekstą]

Esta dissertação aborda o cálculo da taxa de crescimento da tensão de restabelecimento transitória (TCTRT), considerando o caso de falha na barra, durante a abertura do primeiro polo e o cálculo da tensão de restabelecimento transitória (TRT) nos primeiros instantes de tempo, incluindo o efeito da capacitância. Os principais casos possíveis de falha na barra foram analisados e os resultados demonstraram a precisão das expressões obtidas. Normalmente, o cálculo da TCTRT e da TRT é feito por meio de simulações em programas de transitórios eletromagnéticos em que há rotinas específicas para a extração dos valores destas, porém, em determinadas condições, podem ocorrer oscilações ou imprecisões numéricas. Por ser um assunto de grande interesse convém desenvolver expressões que possam esclarecer resultados duvidosos sem a necessidade de artifícios de redução do passo de integração a valores muitas vezes não factíveis. As expressões obtidas neste trabalho podem ser utilizadas não só para se obter de forma precisa e simplificada os valores da taxa de crescimento da tensão de restabelecimento transitória de um circuito real, assim como os valores da TRT nos primeiros instantes de tempo. / This study is focused on the rate of rise of transient recovery voltage (RRTRV) calculation considering the case of bus fault, during the first pole to open, and also includes the transient recovery voltage (TRV) calculation, in the first instants of time, including the capacitance effect. The main cases of bus fault have been evaluated and demonstrate that the expressions developed in this study are relevant and with good precision. Usually, the RRTRV and the TRV are calculated with the use of simulation programs, using specific routines, nevertheless, in certain conditions, there might be oscillations and numeric imprecisions which requires a mathematic expression. This topic is of great interest and it is important to have mathematical expressions that could clarify doubtful results. The expressions obtained in this study can be use in a very simples and effective mode to calculate RRTRV and the TRV in the first instants of time, considering a real life circuit.