Dissertations / Theses: 'Corona (Electricity)'

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Peyda, Arash. "Étude numérique et expérimentale pour déterminer le champ électrique d'apparition des décharges couronnes à l'aide de la configuration d'électrodes tige-plan = Numerical and experimental investigation to determine corona inception electric field for rod-plane electrode configuration /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.

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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2006.
La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQCU Bibliogr.: f. 98-101. Document électronique également accessible en format PDF. CaQCU

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Meyer, Nicholas August. "Mitigation of ozone production by negative corona using electrode wire heating." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07112009-040234/.

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Lopes, Selma Aparecida 1974. "Estudos de propriedades de não tecidos de polipropileno tratados por descarga corona e plasma de rádio frequência." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266705.

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Orientador: João Sinézio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O material polimérico denominado não tecido de polipropileno (NTPP), após receber adequado tratamento químico, tem sido largamente utilizado na indústria têxtil para confecção de produtos de higiene pessoal, fraldas e absorventes descartáveis. Neste sentido o presente trabalho analisa os efeitos das técnicas de descarga corona (atmosfera ambiente) e plasma por radiofrequência (atmosferas de oxigênio (O2), nitrogênio (N2) e argônio (Ar) causados nas propriedades de superfície de amostras de NTPP em função do tempo de tratamento e nas respectivas atmosferas citadas. Recortam-se amostras de NTPP com geometria retangular (10x30mm) e espessura média de 40?m. Após tratamentos por corona e plasma submetem-se as amostras ás técnicas de medidas de ângulo de contato (método da gota séssil), de espectrometria em infravermelho (FTIR/ATR), de microscopia eletrônica exploratória (SEM) e de calorimetria diferencial exploratória (DSC); as quais têm por objetivo caracterizar a superfície do material em relação à molhabilidade, a formação de grupos polares, alterações morfológicas e comportamento de volume, respectivamente. Realizaram-se as medidas em quintuplicatas e dentre os resultados pode-se destacar que (i) o ângulo de contato tende a diminuir com o aumento do tratamento tanto corona quanto plasma, indicando que está ocorrendo aumento da molhabilidade do material, assim como comprovado por cálculos de energia livre de superfície (por exemplo: sem tratamento 18 mN/m e após tratamento 87 mN/m); (ii) as espectrometrias em infravermelho indicam a formação de grupos polares (hidroxílicos e carboxílicos); (iii) os termogramas em DSC indicam que não há alterações entre amostras com e sem tratamento, preservando assim propriedades de volume do material (estabilidade térmica de 0 á 135ºC e Tm=162ºC). Cabe ressaltar que realizaram-se medidas sobre a durabilidade do tratamento corona e os resultados mostram satisfatória durabilidade até 4 dias
Abstract: The polymeric material known as non-woven polypropylene (NTPP) upon receiving suitable chemical treatment has been widely used in the textile industry for the manufacture of personal hygiene products, diapers and disposable absorbent. In this sense the present paper analyzes the effects of corona discharge techniques (ambient atmosphere) and plasma radiofrequency (atmospheres of oxygen (O2), nitrogen (N2) and argon (Ar) caused the surface properties of samples as a function NTPP treatment time and the respective atmospheres cited. Samples were cut out NTPP rectangular geometry (10x30mm) and an average thickness of 40?m. After corona treatment and plasma samples were subjected techniques measures the contact angle (sessile drop method), infrared spectrometry (FTIR/ATR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) which are intended to characterize the material surface with respect to wettability, the formation of polar groups, and morphological behavior volume, respectively. There were measures in quintuplicatas and among the results can be noted that (i) the contact angle tends to decrease with the increase in both corona treatment and plasma, indicating that it is an increase of the wettability of the material, as evidenced by calculations of surface free energy (for example, untreated 18 mN/m after treatment 87 mN/m; (ii) infrared spectroscopy indicated the formation of polar groups (hydroxyl and carboxyl); (iii) the DSC thermograms show no charges between treated and untreated samples, thus maintaining properties of the material volume (thermal stability of 0 to 135ºC and Tm=162ºC). It should be noted that measurements were performed on the stability of the corona treatment and the results show satisfactory stability up to 4 days
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

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Atkinson, R. Dwight. "Corona switching: an osmogene mitigation technique." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/49920.

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Odorous gases such as hydrogen sulfide have long been associated with wastewater treatment plants, especially those with long forced mains which allow septic conditions to develop. With the encroachment of urban and suburban populations, many wastewater treatment plants are no longer located far enough from residential areas to prevent odor problems. This has lead to renewed efforts to develop odor control techniques. The application of high energy coronas as a means to oxidize odorous gases has been limited by the relatively small size of the corona region around a given charged wire, approximately 1 centimeter at an applied voltage of 35 kilovolts. Attempts to enlarge the effective corona region by spacing wires such that their coronas would overlap have failed due to corona extinction, the destructive interference of the electric fields surrounding adjacent charged wires. This study demonstrates that corona extinction can be avoided in a system of closely spaced wires flanked by grounded plates if the wires are energized individually instead of' simultaneously. By employing a rapid load-switching technique an essentially continuous corona sheet can be produced. A bench-scale device utilizing the rapid switching principle was constructed and its ability to remove odorous gases, including hydrogen sulfide, was demonstrated. The influence of parameters such as flowrate, inlet concentration, switching frequency, temperature, and humidity on removal efficiency was evaluated.
Ph. D.
incomplete_metadata

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Du, Toit Nicolaas Serdyn. "Calibration of UV-sensitive camera for corona detection." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/1016.

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Dorris, Kevin Scott. "A possible new source of nitrogen oxides : atmospheric electrical corona." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/25885.

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Evans, John Lee. "Corona discharge and arcing around wires under the influence of high electric fields." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52118/.

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An Electromagnetic Pulse (EMP) resulting from, for example, the detonation of a nuclear weapon is characterised by a wave of electromagnetic activity able to couple with power lines and electro-sensitive equipment with the potential of rendering an establishment or on a greater scale, a whole city impotent. Protection against such occurrences is of paramount importance. It is now accepted that an important consideration when devising protective schemes against such phenomena is an accurate understanding of the effects on propagating waveforms such as those coupled to wires, when electrical breakdown of the dielectric material surrounding such wires occurs, otherwise known as electrical discharge. Such issues can occur around the affected wires if the electric fields generated exceed the dielectric strength of the surrounding medium, typically air or soil. Under these circumstances, the signature of the coupled waveform is known to change in characteristic ways. The form and degree of distortion needs to be understood if the harmful effects are to be prevented by protection systems put in place. The purpose of this thesis is to first describe the mechanisms that lead to the development of the Nuclear–Electromagnetic Pulse (NEMP) and the mechanisms of the discharge that can result once such pulses have coupled to a wire. Next, some of the previous corona-modelling approaches are discussed. Many of the modelling approaches have been applied to 1-D transmission-line simulations. When 3-D simulations have been performed, the Finite-Difference (Time Domain) or FD-TD approach seems to be the preferred method. At the time of writing, no 3-D Transmission Line simulations of discharge phenomena around wires were available. Hence, here, the 3-D Transmission Line Modelling Method (TLM) is described with a view to modelling such behaviour. In particular, the Embedded-Wire-Node (EWN) is used to model the discharge development around the wire. This is a fine-wire technique used to reduce computational fatigue. The node can be adapted to accept changes related to electrical discharge allowing for a real-time, self-consistent recreation of such effects. The 3-D TLM approach proves to be a decent candidate to the modelling of such behaviour. Both advantages and disadvantages of this method are discussed.

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Urban, Rodney Gordon. "Power line corona noise prediction from small cage measurement." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50063.

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Thesis (PhD) -- Stellenbosch University, 2004.
Some digitised pages may appear illegible due to the condition of the original hard copy.
ENGLISH ABSTRACT: The radio noise (RN) performance of an AC high voltage transmission line is a determining factor when accessing the reliability of the design. The conducted RN level across the terminals of a PLC receiver, used in the teleprotection system of the line, is of particular concern. In this dissertation, existing empirical and semi-analytical RN prediction methods are evaluated by comparing the conducted RN levels of four South African lines to the predicted levels. Existing RN measurement protocols are consolidated and a new RN measurement protocol is proposed for the comparison. A prediction methodology, based on the EdF, EPRI and IREQ semi-analytical methods, is formulated. The semi-analytical methods are not able to accurately predict the variation of the conducted RN with frequency in the PLC band, nor are they able to predict the RN performance of short lines. A wideband excitation function, which considers the statistical characteristics of the measured RN pulse train, is therefore proposed in this dissertation. Having investigated the extraction of this excitation function from ESKOM’s Megawatt Park corona cage, it is concluded that a small corona cage is required. The design of a small cage is presented and the extraction of the excitation function is described. Attention is given to assessing the effect of changes in space charge distributions. The effect of space charge collision with an insulated cage on the extracted pulse parameters is linear, provided space charge diffusion is negligible. The onset streamer, positive streamer and negative streamer corona modes were identified as the only modes with measurable RN in the frequency regime 150 kHz to 30 MHz. Formulas are derived for the prediction of the inception gradients for these modes. The RN performance of an ACSR Hare conductor is extracted from the small cage. The RN performance of the Acacia-Koeberg line is also approximated in the PLC band. The dissertation concludes that the proposed wideband excitation function method is capable of accurately predicting the variation of RN levels with frequency. It can also be used to predict the RN performance of short line sections, as well as the relationship between RMS, QP and average RN levels from a transmission line.
AFRIKAANSE OPSOMMING: Die korona-werkverrigting van ‘n WS hoogspanningstransmissielyn het belangrike gevolge vir die betroubaarheid van die ontwerp van die lyn. Die geleide radioruis (RR) vlak op die kraglyndragolf kommunikasie sisteem, wat vir tele-beveiliging gebruik word, is veral van belang. In hierdie werkstuk word bestaande metodes gebruik om die korona-werkverrigting te bepaal en dan met gemete waardes van vier Suid Afrikaanse lyne te vergelyk. Bestaande RR meetmetodes word saamgevat en ‘n nuwe metingsprotokol word voorgestel om resultate te vergelyk. Na aanleiding van hierdie vergelykings word ‘n tegniek ontwikkel om die RR van ‘n lyn te voorspel. Hierdie tegniek gebruik die EdF, EPRI en IREQ metodes. Die voorgestelde tegniek kan nie die verandering van die RR met frekwensie bepaal nie. Dit kan ook nie die RR van kort lyne bepaal nie. ‘n Wyeband RR bron word dus voorgestel. Nadat ESKOM se Megawatt Park korona-kou ondersoek is, is die gevolgtrekking gemaak dat ‘n klein koronakou die nodige wyeband RR bron sal voorsien. Ruimtelading bots met die klein korona-kou. Die effek van hierdie botsings op die pulsparameters is lineer indien ladingsdiffusie nie plaasvind nie. Die aanvangs, positiewe en negatiewe kanaalontladings (“streamers”) is identifiseer as die enigste koronamodusse wat RR veroorsaak tussen 150 kHz en 30 MHz. Die spanning waarby hierdie modusse voorkom, is bepaal. Die korona-werkverrigting van ‘n “ACSR Hare” geleier is bepaal. Die korona-werkverrigting van die Acacia-Koeberg transmissie lyn is ook gekwantifiseer by die kraglyn-dragolf kommunikasie frekwensies. Die wyebandbron metode kan die verandering in RR met frekwensie goed voorspel. Die nuwe metode kan ook gebruik word om die RR van kort lyne te bepaal, asook die verband tussen RMS, QP en gemiddelde RR vlakke.

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Hansell, Fredrik, and Axel Vällfors. "Demand Side Management : how has residential electricity demand changed during the corona pandemic?" Thesis, KTH, Energiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298849.

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Restrictive social distancing measures imposed by governments across the world to prevent the spread of COVID-19 have led to immediate changes in general behaviour and habits, which has had major effects on electricity systems. The pandemic has highlighted the great importance of reliable electricity supply in society as many people were forced to start working from home and thus became entirely reliant on digital modes of communication and information sharing. However, the resilience of energy systems could become weakened in the future as the share of intermittent renewable energy sources keeps increasing. If working from home were to become the norm in the future, knowing how households’ electricity load curves are affected by such a change could be valuable and help increase capabilities of demand side flexibility in the household sector. In this project, appliance-level electricity demand data gathered from Swedish households is used to create a simple bottom-up model. The purpose of the model is to be able to evaluate how the total electricity demand in a residential area changes after implementing behavioral changes at a household level. Specifically, the model was used to evaluate the effect of certain households in a region switching to working from home. Results were obtained from the model in the form of estimated changes in the electricity demand for different proportions of teleworking households. These changes were then combined with electricity demand data from a residential area in Stockholm to create new load curves that show what electricity demand could look like for the residential area at different shares of households working from home. The final results are presented in the form of estimated changes in electricity demand, peak power and electricity consumption for 30, 60 and 90 percent of households working from home.The results showed that weekdays' average load profile may have changed considerably in 2020 for residential areas similar to the one studied in Stockholm. For all scenarios, the change in electricity demand was most noticeable in the middle of the day, when the peak power increased significantly. During the evening, however, neither the electricity demand nor the power peak changed significantly. The peak power during normal working hours increased by 11,6% to 17,1% depending on the season, while total electricity consumption on an average weekday increased by 4,9% to 7,4% compared to pre-pandemic values. Still, the overall weekday power peak typically occurring around dinner time remained nearly unchanged. However, examining the results for different shares of households working from home shows that if almost all were to work from home, the overall peak power could shift from occurring in the evening to the middle of the day. If a new measurement campaign of Swedish households were to be conducted in the future, the ability to predict and prepare for the electricity demand of tomorrow’s homes would improve greatly.
I ett försök att förhindra spridningen av viruset COVID-19 har länder världen över infört sociala restriktioner som i många fall medfört drastiska förändringar av invånarnas vanor och beteenden samt en omfattande påverkan på landets elsystem. Pandemin har framhävt vikten av tillförlitlig elförsörjning i samhället i och med att många har tvingats börja arbeta hemifrån och således blivit helt beroende av digital kommunikation och informationsdelning. Energisystemens motståndskraft kan dock komma att försvagas i framtiden i takt med att andelen intermittenta förnybara energikällor fortsätter att öka. Om distansarbete skulle bli det nya normala i framtiden kan det vara värdefullt att känna till hur det påverkar hushållens belastningskurvor. Kunskapen kan även bidra till ökade möjligheter för flexibilitet på efterfrågesidan i hushållssektorn. I det här projektet används elbehovsdata på apparatnivå från ett stort antal svenska hushåll för att skapa en enkel bottom-up-modell över hushålls elförbrukning. Modellens syfte är att genom implementering av beteendeförändringar på en hushållsnivå kunna utvärdera hur det totala elbehovet i ett bostadsområde förändras. Specifikt användes modellen för att utvärdera effekten av att vissa hushåll i en region går över till distansarbete. Resultat erhölls från modellen i form av uppskattade förändringar av elbehovet vid olika andelar distansarbetande hushåll. Dessaförändringar kombinerades sedan med elbehovsdata från ett bostadsområde i Stockholm för attskapa nya belastningskurvor som visar hur elbehovet kan se ut för bostadsområdet vid olikaandelar distansarbetande hushåll. De slutgiltiga resultaten presenteras i form av uppskattade förändringar av elbehov, effekttoppar och elförbrukning vid 30, 60 och 90 procents andel distansarbetande hushåll. Resultaten visade att vardagars genomsnittliga belastningsprofil kan ha förändrats markant under 2020 för bostadsområden likt den studerade i Stockholm. För samtliga scenarier var förändringen i elbehovet mest märkbar mitt på dagen då effekttoppen ökade avsevärt. Under kvällstid förändrades dock varken elbehovet eller effekttoppen avsevärt. Effekttoppen under normala arbetstider ökade mellan 11,6% och 17,1% beroende på årstid, medan elförbrukningenen genomsnittlig vardag ökade med mellan 4,9% och 7,4% jämfört med innan pandemin. Kvällens effekttopp, som vanligtvis inträffar runt middagstid, var i princip oförändrad. Däremot visar resultaten att i ett scenario där en mycket hög andel av befolkningen arbetar hemifrån kan den högsta effekttoppen inträffa mitt på dagen istället för på kvällen. För framtiden skulle en ny mätkampanj som kartlägger de svenska hushållens elförbrukning kunna medföra ökade möjligheter för samhället att förbereda sig inför och förutse morgondagens elbehov.

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Silva, Rodrigo Cleber da [UNESP]. "Inclusão das representações de gary e de skilling-umoto em modelos de linhas de transmissão trifásicas: Aplicação em simulações de transitórios eletromagnéticos em sistemas de energia elétrica." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/134103.

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Made available in DSpace on 2016-02-05T18:29:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-25. Added 1 bitstream(s) on 2016-02-05T18:33:44Z : No. of bitstreams: 1 000857565.pdf: 1726285 bytes, checksum: acf252e5a46ceced5c2b1b64ccd59cc7 (MD5)
Neste projeto é desenvolvido um modelo de linha de transmissão trifásica em que possa ser incluído o efeito corona. O modelo será desenvolvido diretamente no domínio do tempo e o mesmo baseia-se na hipótese de que um pequeno segmento de linha trifásica pode ser representado por um circuito constituído por elementos discretos (resistências, indutâncias, capacitâncias e condutâncias). A inserção do efeito corona no modelo da linha será feito com base nos modelos de Gary e de Skilling-Umoto que, até o presente momento, é utilizado para inserir o efeito corona em modelos de linhas de transmissão monofásicas. O modelo a ser desenvolvido poderá ser utilizado para representar linhas trifásicas genéricas, independentemente da geometria da mesma, em simulações de transitórios eletromagnéticos que podem ocorrer em sistemas de energia elétrica. A grande contribuição que resultará do desenvolvimento deste projeto será a disponibilização de um modelo de linha mais completo que os modelos disponíveis atualmente, pois o modelo proposto poderá ser aplicado em qualquer linha trifásica, independentemente da geometria da mesma, e levará em conta o efeito corona (que é responsável por distorções nas formas de ondas de correntes e tensões que se propagam ao longo da linha durante a ocorrência de distúrbios). Um modelo de linha mais precisa que prevê tais distorções, poderá ser útil na análise do sistema de proteção, permitindo um ajuste mais preciso e aumentando a confiabilidade do sistema de energia elétrica
In this project will be developed a model for three-phase transmission line that may be included in the corona effect. The model will be developed directly in the time domain and the same is based on the hypothesis that a short segment of three phase line can be represented by a circuit constituted by discrete elements (resistance, inductance, capacitance, and conductance). The insertion of the corona effect in the line model will be based on Gary and Skilling-Umoto models that, until the present time, is used to insert the corona effect in models of transmission lines monophasic. The model to be developed can be utilized to represent generic three-phase lines, regardless of the line geometry, in electromagnetic transient simulations that can occur in electrical power systems. The great contribution that will result from the development of this project will be the making available of a model line more complete than the currently available models, since the proposed model can be applied to any three-phase line, regardless of the geometry of the line, and will take into consideration the corona effect (which is responsible for distortions in the waveforms of voltages and currents that propagate along the line during the occurrence of disturbance). A more accurate model line that provides for such distortions may be useful in the analysis of the protection system, allowing for a more precise fit and increasing the reliability of the electric power system

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Silva, Rodrigo Cleber da. "Inclusão das representações de gary e de skilling-umoto em modelos de linhas de transmissão trifásicas: Aplicação em simulações de transitórios eletromagnéticos em sistemas de energia elétrica /." Ilha Solteira, 2015. http://hdl.handle.net/11449/134103.

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Orientador: Sérgio Kurokawa
Banca: Luis Carlos Origa de Oliveira
Banca: Mariangela Carvalho Bovolato
Banca: José Pissolato Filho
Banca: Eduardo Coelho Marques da Costa
Resumo: Neste projeto é desenvolvido um modelo de linha de transmissão trifásica em que possa ser incluído o efeito corona. O modelo será desenvolvido diretamente no domínio do tempo e o mesmo baseia-se na hipótese de que um pequeno segmento de linha trifásica pode ser representado por um circuito constituído por elementos discretos (resistências, indutâncias, capacitâncias e condutâncias). A inserção do efeito corona no modelo da linha será feito com base nos modelos de Gary e de Skilling-Umoto que, até o presente momento, é utilizado para inserir o efeito corona em modelos de linhas de transmissão monofásicas. O modelo a ser desenvolvido poderá ser utilizado para representar linhas trifásicas genéricas, independentemente da geometria da mesma, em simulações de transitórios eletromagnéticos que podem ocorrer em sistemas de energia elétrica. A grande contribuição que resultará do desenvolvimento deste projeto será a disponibilização de um modelo de linha mais completo que os modelos disponíveis atualmente, pois o modelo proposto poderá ser aplicado em qualquer linha trifásica, independentemente da geometria da mesma, e levará em conta o efeito corona (que é responsável por distorções nas formas de ondas de correntes e tensões que se propagam ao longo da linha durante a ocorrência de distúrbios). Um modelo de linha mais precisa que prevê tais distorções, poderá ser útil na análise do sistema de proteção, permitindo um ajuste mais preciso e aumentando a confiabilidade do sistema de energia elétrica
Abstract: In this project will be developed a model for three-phase transmission line that may be included in the corona effect. The model will be developed directly in the time domain and the same is based on the hypothesis that a short segment of three phase line can be represented by a circuit constituted by discrete elements (resistance, inductance, capacitance, and conductance). The insertion of the corona effect in the line model will be based on Gary and Skilling-Umoto models that, until the present time, is used to insert the corona effect in models of transmission lines monophasic. The model to be developed can be utilized to represent generic three-phase lines, regardless of the line geometry, in electromagnetic transient simulations that can occur in electrical power systems. The great contribution that will result from the development of this project will be the making available of a model line more complete than the currently available models, since the proposed model can be applied to any three-phase line, regardless of the geometry of the line, and will take into consideration the corona effect (which is responsible for distortions in the waveforms of voltages and currents that propagate along the line during the occurrence of disturbance). A more accurate model line that provides for such distortions may be useful in the analysis of the protection system, allowing for a more precise fit and increasing the reliability of the electric power system
Doutor

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Xiao, Fuchun Safety Science Faculty of Science UNSW. "Electrostatic charging of water sprays by corona and induction for dust suppression." Awarded by:University of New South Wales. School of Safety Science, 2000. http://handle.unsw.edu.au/1959.4/27410.

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Dust control is a very significant issue in underground coal mining. The benefits of reducing dust levels will be a lesser risk of lung disease to coal miners, improved working conditions and a reduced risk of dust explosions. Coal dust is commonly suppressed by water sprays but suppression efficiency is not high because dust tends to travel in the air flow round the water droplets rather than being captured by them. If water sprays are electrostatically charged, then a significant improvement in dust suppression efficiency may be achieved. Of the three principal droplet charging mechanisms, i.e. corona charging, induction charging and contact charging, corona charging is the most widely used in many industrial fields including dust suppression, However, it requires a high applied voltage, ranging from thousands to more than a hundred thousand volts, depending on the geometry of the charging equipment. Induction charging has been used in agricultural spraying since Law (1978) developed an embedded-electrode induction charging spraying nozzle. This nozzle provides a compact, inexpensively fabricated droplet charger and, reduces design requirements on size and output voltage (of the order of 1000 volts). It also reduces the potential for mechanical damage, misalignment and personnel hazard. In order to evaluate the effectiveness of dust suppression, either the charge on individual droplets or the charge-to-mass ratio of water sprays needs to be known. However, the parameters which control the charge applied to water and the charging rate have been unsolved theoretically for any charging mechanism. The existing theories for the induction-charged and air-atomising a liquid jet have been found to be inadequate. And there is no theory available for corona charging of the droplets produced with a pneumatic nozzle in order to predict the spray charge level or the spray charge-to-mass ratio. In view of this situation, mathematical models have been developed in this thesis for both the corona and induction charging mechanisms. During the development of the theories, it has been assumed that for corona charging, that the jet is disintegrated into droplets and the droplets are then charged; for induction charging, that the jet is first charged and the charged jet is then disintegrated into charged droplets. The Sauter mean diameter of the sprays, D32 , plays an important role in linking the individual droplet charge to the spray charge-to-mass ratio for both charging mechanisms. The developed theories are general models suitable for any liquid with both corona and induction charging. Theoretical calculations for the spray charge-to-mass ratio, individual droplet charge and the ratio of droplet charge to the Rayleigh charge limit have been presented for almost all of the influencing electrical and mechanical parameters such as applied voltage, air flowrate, liquid flowrate, liquid conductivity, liquid dielectric constant, nozzle dimensions, cylindrical electrode dimensions, and fluid parameters, for example, density, viscosity and surface tension. In the calculation for corona charging of droplets, the effect of the droplets on corona current and corona-onset voltage has been assessed for first time. The introduction of the Sauter mean diameter of the sprays, D32 , makes the assessment possible. Theoretical calculations for induction charging of liquid jets have shown that provided liquids have a conductivity value higher than the critical value, s = - 10 4 S/m, then they can be charged satisfactorily by the induction charging method. Among all of the influencing parameters, the electrical and mechanical parameters determine the charging rate and the water spray charge level. The suitability of employing these two charging mechanisms to dust suppression in coal mine has been evaluated based on the spray charge level, safety issues and the simplicity or otherwise of the equipment. The induction charging method was considered to have advantages over its corona charging counterpart, and has been chosen for charging the water sprays in the experiment program. Water has a conductivity of s = - 10 2 S/m, higher than the critical value, s = - 10 4 S/m. Based upon theoretical considerations, it is concluded that water is an appropriate liquid for corona charging, based on its dielectric constant, and for induction charging, based on its conductivity. In order to facilitate the testing of electrostatically charged water spray cloud parameters, a spray charger/collector was designed and constructed by others and a computerised data acquisition system has been employed. According to the theory developed for induction charging, the optimum length of the charging electrode has been analysed based upon the assumption that water jet is first charged and then the charged jet is disintegrated into charged droplets by the high pressure air. An experimental program examined the dependence of spray current upon four parameters: air flowrate, water flowrate, applied voltage and jet diameter. The experiments have shown that the induction-charged air-atomising nozzle used in the experiment is able to impart a significant charge into the water sprays. The spray charge-to-mass ratio calculated based upon the measured spray current demonstrates the same characteristics as predicted by theory: increasing with air flowrate, decreasing with water flowrate, increasing with applied voltage to a peak value then decreasing with further increase in the voltage, and increasing with jet diameter. A successful interpretation of an important phenomenon in the inductioncharged air-atomising a water jet, that spray charge-to-mass ratio and spray current increase with air pressure (or air flowrate) and decrease with increasing water flowrate, has been achieved based on the theories developed in this thesis. This phenomenon occurs because increasing air flowrate and/or decreasing water flowrate leads to a higher velocity of jet flowing through the induction electrode. However, when water flowrate becomes very small, a decrease in spray current with increasing air pressure (or flowrate) may be caused both by jet breakup inside the electrode and by contraction of the jet. In order to verify the theory, a preliminary comparison of experimental data with theoretical predictions employing a constant kic in the air-jet interaction coefficient a which was assumed to be 0.7 has shown a general agreement. However, the value of kic appears to be related to jet diameter, air/water mass ratio and applied voltage. An empirical equation for kic has then been formulated based on the experimental data for the spray charge-to-mass ratio. Finally a comparison of experimental results with theoretical predictions using the formulated kic shows an improved agreement. It is concluded that the induction-charged air-atomising nozzle has a potential application in dust suppression in coal mines, as the voltage required to charge water sprays is only 1000 ~ 1200 volts, and that the theory developed for induction charging of water sprays can be used to guide laboratory investigations and design processes for dust suppression and other industrial applications which might employ the electrostatic charging of liquid sprays.

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13

Morys, Marcin M. "Patch antenna characterization in a high-voltage corona plasma." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50324.

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In order to improve efficiency and reliability of the world's power grids, sensors are being deployed for constant status monitoring. Placing inexpensive wireless sensors on high-voltage power lines presents a new challenge to the RF engineer. Large electric field intensities can exist around a wireless sensor antenna on a high-voltage power line, leading to the formation of a corona plasma. A corona plasma is a partially ionized volume of air formed through energetic electron-molecule collisions mediated by a strong electric field. This corona can contain large densities of free electrons which act as a conducting medium, absorbing RF energy and detuning the sensor's antenna. Through the use of low-profile antennas and rounded geometries, the possibility for corona formation on the antenna surface is greatly reduced, as compared with wire antennas. This study looks at the effects of a corona plasma on a patch antenna, which could be used in a power line sensor. The corona's behavior in the presence of an electromagnetic plane wave is analyzed mathematically to understand the dependence of attenuation on frequency and electron density. A Drude model is used to convert plasma parameters such as electron density and collision frequency to a complex permittivity that can be incorporated in antenna simulations. Using CST Microwave Studio, a 5.8 GHz patch antenna is simulated with a plasma material on its surface, of varying densities and thicknesses. Power absorption by the plasma dominates the power loss, as opposed to detuning. A wideband patch is simulated to show that the detuning effects by the plasma can be further reduced. Power absorption by the plasma is significant for electron densities greater than 10¹⁸ m⁻³. However, small point corona are found to have little effect on antenna radiation.

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14

Carvalho, José Geraldo de 1977. "Tratamentos térmico e corona em tecido de poliéster." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266853.

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Orientador: João Sinézio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-18T13:11:39Z (GMT). No. of bitstreams: 1 Carvalho_JoseGeraldode_M.pdf: 906811 bytes, checksum: ac36e65d7b8b81bace165c355c2d5f59 (MD5) Previous issue date: 2011
Resumo: O tratamento térmico, que na indústria têxtil é mais conhecido como termofixação, é um processo muito importante para garantir a estabilidade dimensional do tecido de poliéster durante os processos de beneficiamento e no uso. Mas o processo de termofixação modifica algumas propriedades do tecido e entre elas podemos destacar: Hidrofilidade, comportamento tintorial, alongamento e ruptura. Essas propriedades são influenciadas pelas variáveis tempo e temperatura de termofixação. Nesse sentido o presente trabalho tem como objetivo analisar as alterações proporcionadas pela termofixação nas propriedades físico-químicas do tecido de poliéster. O poliéster é um material que apresenta superfície quimicamente inerte, não porosa e com baixa energia de superfície (43 mN/m). O tratamento com descarga corona vem propor aumentar a energia de superfície, melhorar a hidrofilidade, o comportamento tintorial e a adesão do tecido termofixado e sem termofixar. Submeteram-se amostras de tecido plano de poliéster á termofixação em diversas combinações de tempo e temperatura dentro dos intervalos de 120 a 220°C e de 30 a 120 segundos. Após a termofixação mediu-se o encolhimento das amostras e submeteram-se as mesmas a testes de alongamento e ruptura. Trataram-se amostras de tecido de poliéster termofixadas e sem termofixar com descarga corona, e em seguida, submeteu-se as mesmas a testes de hidrofilidade, tingimento, estampagem, alongamento e ruptura. Observou-se que a termofixação promove encolhimento, aumento do alongamento, diminuição da hidrofilidade e da absorção de corante em tingimento de tecido de poliéster. O tratamento corona aumenta a hidrofilidade, a absorção de corante, a ancoragem de pigmentos em amostras de tecido de poliéster termofixadas e sem termofixar
Abstract: The thermal treatment, which in the textile industry is known as heat setting, is very important to ensure the dimensional stability of polyester fabric during the process of improving and use. But the process of heat setting changes some properties of the fabric and among them we can highlight: Hidrophilicity, dyeability, elongation and strength. These properties are influenced by variables dwell time and heat setting temperature. In that sense this work has as objective to analyze the changes caused by heat in the physico-chemical properties of polyester fabric. Polyester is a material that presents the surface chemically inert, non-porous and low surface energy (43 mN / m). The treatment with corona discharge is proposing to increase the surface energy, improve the hidrophilicity, dyeability and adhesion of the polyester fabric with and without heat setting. Samples of polyester plan fabric underwent to heat setting on various combinations of time and temperature within the interval between 120 to 220 ° C, from 30 to 120 seconds. After the heat setting was measured the shrinkage of the samples and underwent the samples by tests of elongation and rupture. Samples of polyester fabric with and without heat setting were treated with corona discharge and in sequence the samples were tested by hidrophilicity, dyeing and printing. The heat setting promotes shrinkage and increase the elongation of polyester fabric. It was observed that the heat setting promotes shrinkage, increase of elongation, reduction of hydrophilicity and reduction of uptake of dye in the dyeing of polyester fabric. The corona treatment increase the hydrophilicity, the absorption of dye in pad-thermofix process and the pigment anchoring in polyester fabric samples with and without heat setting
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

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15

Sena, Hildo Costa de. "Efeitos da descarga corona em superfície de polipropileno em temperatura ambiente e acima." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266860.

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Orientador: João Sinézio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-17T16:49:59Z (GMT). No. of bitstreams: 1 Sena_HildoCostade_M.pdf: 22003439 bytes, checksum: 1eca2b2806567e926cea6f94abd18776 (MD5) Previous issue date: 2011
Resumo: Este trabalho avalia o efeito do tratamento por descarga corona em temperatura ambiente e acima para promover aumento da energia de superfície em filmes de polipropileno (PP). Submeteram-se amostras de polipropileno ao tratamento corona em sistema com geometria ponta-plano e utilizou-se de tensão de polarização dos eletrodos em 5kV . Avaliaram-se os efeitos do tratamento corona através de medidas de ângulo de contato pelo método da gota séssil, em função dos parâmetros: tempo de tratamento corona (2s a 90s), temperatura das amostras de polipropileno (25_C e 55_C) e distância entre os eletrodos (3mm e 5mm). Os resultados indicam influência significativa do tempo de tratamento corona e da distância intereletrodos. Ademais, o tratamento corona aumenta a energia de superfície dos filmes observada através da diminuição do valor do ângulo de contato entre amostra e gota d'água (inicialmente 88_ sem tratamento e 50_ após corona com 3mm de distância entre os eletrodos). Dentre os parâmetros e condições estudadas a temperatura não apresenta influência nos valores de ângulo de contato a fim de mudar a energia de superfície dos filmes. Em adição as medidas de ângulo de contato, medem-se propriedades físico-químicas da superfície do PP através da obtenção dos espectros dos filmes por espectrometria de infravermelho com transformações de Fourier (FT-IR) e de micrografias obtidas por microscopia eletrônica exploratória (MEV). A energia de superfície (antes e após tratamento corona) foi determinada utilizando-se os seguintes métodos: tensão superficial crítica (c), equação de estado (EE) e as aproximações de Owens/ Wendt (OW), Wu (Wu) e van Oss/ Chaudhury/ Good (VCG). A partir destes métodos encontra-se que: foram observadas diferenças entre os espectros de FT-IR obtidos nas diferentes condições de tratamento estudadas quando associadas a modificação por corona sob temperatura acima da ambiente (55_C _ 2_C). Alterações na topografia dos filmes de PP foram observadas após tratamento por descarga corona através da formação de grânulos, depressões, eriçamento e protuberâncias na superfície destes. Melhorias na energia livre superficial dos filmes de PP foram observadas após tratamento corona e variou aproximadamente de 36,9mN=m para 47,9mN=m em filmes sem tratamento superficial e após 10s de tratamento por descarga corona quando determinada através da aproximação de VCG, respectivamente
Abstract: The present study evaluates the effect of corona discharge treatment at room temperature and above in order to promote an increase of surface energy of polypropylene films. Polypropylene samples were subjected to corona treatment in tip-plane geometry system using bias voltage of 5kV between the electrodes. The effects of corona treatment were assessed by contact angle measurements using the sessile drop method, taking in account the following parameters: corona treatment time (2s to 90s), temperature of polypropylene samples (25_C and 55_C) and distance between the electrodes (3mm and 5mm). The results indicate significant influence of treatment time and the distance between the electrodes. Moreover, the corona treatment increases the surface energy of the films which was observed by decreasing the value of the contact angle between thesample and drop of water (initially 88_ without treatment and 50_ after corona with 3mm gap between the electrodes). Among the parameters and conditions studied, the temperature does not influence the values of contact angle in order to change the surface energy of the films. In addition the measures of contact angle, were carried out measures of physicochemical properties of the PP surface by obtaining the spectra of the films by infrared spectrometry with Fourier transformed (FT-IR) and micrographs obtained by scanning electron microscopy (SEM). The surface energy (before and after corona treatment) was determined using the following methods: critical surface tension (c), equation of state (EE) and approaches from Owens/ Wendt (OW), Wu (Wu) and van Oss/ Chaudhury/ Good (VCG). From these methods is turning out that: there were differences between the spectra obtained at different FT-IR treatment conditions studied when associate the corona modification at above room temperature (55_C _ 2_C). Changes in the topography of the films PP were observed after treatment by corona discharge due to formation of granules, depressions, bristling and bumps on their surface. Improvements in surface free energy of the PP films were observed after corona treatment, around from about 36,9mN=m in films without surface treatment up to 47,9mN=m after 10s of corona discharge when determined by VCG approach
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

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16

Otto, Abraham Johannes. "Direct current conductor corona modelling and metrology." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1497.

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Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Prospects of up-rating existing high voltage direct current (HVDC) transmission schemes, as well as the conversion of existing alternating current (AC) to direct current (DC) lines and the development of new HVDC schemes in sub-Saharan Africa, have led to renewed interest in DC research. The radio interference (RI), audible noise (AN) and corona loss (CL) performance of HVDC transmission lines are critical factors when assessing the reliability of the line design. The RI performance is especially important when considering the successful transmission of the carrier signal of the power line carrier (PLC) system. The PLC system is the main form of communication between teleprotection devices on the Cahora Bassa HVDC scheme. The aim of the dissertation is to devise modelling as well as metrological techniques to characterise DC conductor corona. A particle-in-cell (PIC) computational code is developed to gain a better understanding of the physical processes that occur during corona events. The numerical code makes use of the charge simulation method (CSM) and nite element method (FEM) to solve for the Laplace and Poisson eld equations. Higher-order basis functions are implemented to obtain a more accurate solution to the Poisson equation. The computational tool yields insight into the mathematical models for the various ionization, attachment and electron avalanche processes that give rise to corona currents. Together with a designed and developed electrometer-type circuit, the numerical code assists the visualisation of the space charge particle dynamics that form in the electrode gap during corona events. The metrological techniques consider the wideband time domain (TD) as well as the frequency domain (FD) information of the measured corona pulses in the presence of noise. These are then compared to the narrowband CISPR standard measurements centred around 500kHz. The importance of impedance matching when attempting to derive a wideband excitation function is investigated. The TD measurements are quite distinct from the well-published FD measurements, and consider the pulse shape, pulse spectrum and pulse repetition rates. The use of three possible conductor corona test methods to study direct current conductor RI performance under both positive and negative polarities is investigated at high altitude in this dissertation. These include a small corona cage, a short test line and the Eskom Megawatt Park large outdoor corona cage. Derived wideband and narrowband monopolar DC RI excitation functions at 500kHz are consolidated with existing radio noise (RN) measurement protocols and prediction methods. The use of a corona cage to derive excitation functions for monopolar RI predictions is explored and it is shown that a small corona cage, due to the build-up of space charge in the small distance between the electrodes, cannot be used to predict the RI levels on HVDC transmission lines accurately. As a consequence of the physics, computational modelling and both frequency and time domain measurements, it is now possible to explain why a small cage system prevents the accurate RI prediction on transmission lines. The large outdoor corona cage and short test line RI performance predictions agree with existing empirical prediction formulas.
AFRIKAANSE OPSOMMING: Vooruitsigte van die opgradering van bestaande hoogspanningsgelykstroom transmissielyn skemas, asook die omkering van bestaande wisselstroom na gelykstroom lyne en die ontwikkeling van nuwe hoogspanningsgelykstroom skemas in sub-Sahara Afrika, het gelei to hernude belangstelling in gelykstroomnavorsing. Die korona-werkverrigting van hoogspanningsgelykstroom oorshoofselyne in terme van radiosteuring, hoorbare-geraas en koronaverliese is kritiese faktore om in aanmerking te neem wanneer die betroubaarheid van die lynontwerp geëvalueer word. Die radiosteuring-werkverrigting is veral van belang tot die suksesvolle oordrag van die kraglyndragolf draersein wat die hoof kommunikasievorm tussen beskermingstoerusting op die Cahora Bassa transmissielyn skema is. Die doel van hierdie proefskrif is om modellering- sowel as meettegnieke te ontwerp om gelykstroomgeleierkorona te karakteriseer. 'n Partikel-in-sel numeriese kode is ontwikkel om 'n beter begrip te verkry van die siese prosesse gedurende koronagebeure. Die numeriese kode maak gebruik van die lading-simulasiemetode, sowel as die eindige element metode om die Laplace en Poisson veldvergelykings op te los. Hoër-orde basisfunksies is geimplimenteer om 'n meer akkurate oplossing vir die Poisson vergelyking te verkry. Die numeriese kode bied insig tot die wiskundige modelle vir die verskeie ionisasie-, aanhegtings- en lawineprosesse wat lei tot koronastrome in die area om die hoogspanningsgeleier. Die numeriese kode, saam met 'n elektro-meter wat ontwerp en ontwikkel is, dra by tot die begrip van die ruimtelading partikeldinamika wat onstaan in die elektrodegaping gedurende koronagebeure. Die meettegnieke neem die wyeband tydgebied- en frekwensiegebiedinformasie van die koronapulse in ag in die teenwoordigheid van geraas. Dit word dan vergelyk met die nouband CISPR meetstandaard vir 'n frekwensie van 500kHz. Die belangrikheid van impedansie-aanpassing vir wyeband metings met die doel om opwekkingsfunksies af te lei, word ondersoek. Die tydgebiedmetings verskil van die algemene frekwensiegebiedmetings, en ondersoek die pulsvorm, -spektrum en -herhalingskoers. Die gebruik van drie moontlike koronageleier-toetsmetodes om gelykstroom radiosteurings-werkverrigting vir positiewe en negatiewe polariteite te bestudeer by hoë vlakke bo seespieël word ondersoek in die proefskrif. Dit sluit in 'n klein koronakou, 'n kort toetslyn en die Eskom Megawatt Park groot buitelug-koronakou. Afgeleide wye- en nouband monopolêre gelykstroom radiosteuring opwekkingsfunksies by 500kHz word gekonsolideer met bestaande radioruis metingsprotokolle en voorspellingsmetodes. Die gebruik van 'n koronakou om opwekkingsfunksies af te lei vir monopolêre radiosteuringvoorspellings is ondersoek en daar is gevind dat 'n klein koronakou nie gebruik kan word om radiosteuringvlakke op hoogspanningsgelykstroom transmissielyne akkuraat te voorspel nie. Dit is as gevolg van die opbou van ruimtelading in die klein elektrodegaping. Met behulp van die sika, numeriese modellering en beide die frekwensie- en tydgebiedmetings, is dit nou moontlik om te verklaar waarom die klein koronakou die akkurate radiosteuringvoorspellings op transmissielyne onmoontlik maak. Die groot buitelug-koronakou en kort toetslyn radiosteuringvoorspellings stem ooreen met bestaande empiriese voorspellings formules.

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17

Bergamasco, Daives Arakem 1976. "Caracterização de propriedades físicas em tecido de seda após tratamento pelos métodos de degomagem e por descarga corona." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266056.

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Orientador: João Sinézio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-26T11:45:54Z (GMT). No. of bitstreams: 1 Bergamasco_DaivesArakem_M.pdf: 2473917 bytes, checksum: f246b9e27a6e46a969245f8ff3666b15 (MD5) Previous issue date: 2015
Resumo: A indústria têxtil vem constantemente investindo tanto no processamento quanto na melhoria de seus produtos. Dentre a gama de materiais se destaca a seda, porém há a necessidade de adequá-la (beneficiamento) no sentido de se obter seu máximo rendimento. O presente trabalho visa apresentar resultados dos processos de degomagem e tratamento corona sobre tecidos de seda por analisar destacadas propriedades físicas tais como hidrofilidade, resistência à tração e perda de massa. Submeteram-se amostras de tecido de seda ao tradicional processo de degomagem com sabão de Marsellha e também pelo processo de tratamento corona. Posteriormente realizaram-se ensaios de hidrofilidade (medidas de ângulo de contato), resistência à tração e perda de massa. Os resultados mostram que: (i) tanto a degomagem quanto o tratamento corona promovem excelente hidrofilidade; no entanto o tempo para completa hidrofilidade é de 45 s quando tratado por corona e de 60 minutos quando por degomagem; (ii) a resistência a tração é maior com o processo corona e (iii) a perda de massa com a degomagem é em média 26% e com o processo corona é de 0,3%. Cabe ressaltar que com o processo corona praticamente não há geração de efluente em comparação com o de degomagem, o que significa outra grande vantagem para a indústria. De acordo com os resultados observam-se grandes vantagens na utilização do processo corona no que tange ao beneficiamento em tecido de seda
Abstract: The textile industry has been constantly investing in the processing and in the improvement of its products. Among the range of materials stands out silk, but there is a need to adjust it (improvement) in order to obtain their maximum efficiency. This paper presents results of degumming processes and corona treatment on silk fabrics by analyzing important physical properties such as hydrophility, tensile strength and weight loss. Underwent silk tissue samples to traditional degumming process Marsellha soap and also for the corona treating process. Subsequently took place hydrophility tests (contact angle measurements), tensile strength and weight loss. The results show that: (i) degumming and corona treatment promote excellent hydrophility; however, the time to complete hydrophility is 45 s when treated by corona and 60 minutes when a degumming; (ii) the tensile strength is higher with the corona process, and (iii) the mass loss is degumming with an average of 26% and the corona process is 0.3%. Note that with the corona process there is no generation of effluent compared to degumming, which means another advantage to the industry. According to the results, there are large advantages in using the corona process with regard to the processing of silk fabric
Mestrado
Ciencia e Tecnologia de Materiais
Mestra em Engenharia Química

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18

Louzi, Vitor César de Almeida 1990. "Estudo do efeito do tratamento corona aplicado a monofilamentos de polímeros sintéticos." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266037.

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Abstract:

Orientador: João Sinézio de Carvalho Campos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Fibras poliméricas sintéticas vêm sendo muito utilizadas em diversas aplicações (medicina, têxtil, etc), especialmente na forma de monofilamentos, com diversos diâmetros, devido às suas características de resistência mecânica. No entanto apresentam baixa hidrofilidade e energia livre de superfície com propriedades adesivas relativamente fracas, limitando assim suas aplicações. Com objetivo de ampliar as aplicações deste material, técnicas estão sendo desenvolvidas no sentido de melhorar estas propriedades, especialmente as de superfície. Dentre as técnicas de modificação de superfície destaca-se a descarga corona a qual pode operar em condições ambientes de temperatura e pressão, sem necessidade de agentes químicos, minimizando a geração de resíduos. Desse modo, o presente trabalho estuda os efeitos promovidos pela descarga corona em três diferentes fibras poliméricas: polipropileno (PP), politereftalato de etileno (PET) e poliamida-6 (PA-6). Amostras desses polímeros foram submetidas à descarga corona sob condições ambientes controladas. O tratamento corona foi realizado em função dos parâmetros: distância entre os eletrodos e tempo de tratamento. Após tratadas, as amostras foram submetidas às técnicas de caracterização: ângulo de contato (Método de Wilhelmy), espectroscopia no infravermelho (FT-IR/ATR), microscopia eletrônica de varredura (MEV), calorimetria exploratória diferencial (DSC), ensaios de tração e absorção de água. Os valores de ângulo de contato dinâmico foram reduzidos em até 29,6%, 27,9% e 18,6% para amostras de PP, PET e PA-6 tratadas, respectivamente. Os valores de energia de superfície aumentaram em 50,3%, 26% e 15% para PP, PET e PA-6. Amostras de PP, PET e PA-6 tratadas por descarga corona (4mm e 120s) apresentaram grau de absorção de água igual a 9,4%, 8,5% e 9,1%. A partir dos resultados obtidos com amostras de monofilamentos de PP, PET e PA-6, sem tratamento e após corona, pode-se concluir que o tratamento corona promove aumento da hidrofilidade e as propriedades térmicas e mecânicas não são afetadas. Palavras-chave: descarga corona, fibras têxteis, monofilamentos poliméricos, polipropileno, politereftalato de etileno, poliamida-6, propriedades de superfície, hidrofilidade, ângulo de contato
Abstract: Synthetic polymer fibers have been widely used in various applications, especially in the form of monofilament and under various diameters, due to its characteristics of mechanical resistance. However synthetic polymer fibers exhibit low hydrophilicity and surface free energy with relatively weak adhesive properties, thus limiting their applications. Aiming to expand the applications of these materials, techniques are being developed to improve these properties, especially the surface. Among modification techniques there is the corona discharge which can operate in ambient temperature and pressure, without the need for chemical agents, minimizing the generation residue. Thus, this research work studies the effects caused by the corona discharge in three different polymeric fibers: polypropylene (PP), polyethylene terephthalate (PET) and polyamide-6 (PA-6). Samples of these polymers were subjected to corona discharge under controlled environmental conditions. The corona treatment was performed on the basis of the parameters: distance between the electrodes and time of treatment. After treated, the samples were subjected to characterization techniques: contact angle (Wilhelmy Method), infrared spectroscopy (FT-IR/ATR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile and water absorption. The dynamic contact angle values were reduced by up to 29,6%, 27,9% and 18,6% for PP, PET and PA-6 treated samples, respectively. The surface energy values increased by 50,3%, 26% and 15% for PP, PET and PA-6. PP, PET and PA-6 samples treated by corona discharge (4mm and 120s), showed the degree of water absorption equal of 9,4%, 8,5% and 9,1%. From the results obtained with samples of PP, PET and PA-6, without treatment and after treatment, can be concluded that the corona treatment enhances the hydrophilicity and the thermal and mechanical properties are not affected. Keywords: corona discharge, textile fibers, monofilament polymer, polypropylene, polyethylene terephthalate, polyamide-6, surface properties, hydrophilicity, contact angle
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química

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19

Pieterse, Cornelius Louwrens. "Mathematical and numerical analysis of electrospraying electrodynamics." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95529.

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Thesis (MEng) -- Stellenbosch University, 2014
ENGLISH ABSTRACT: The electrodynamics of arbitrary, point-to-plane electrospraying geometries, were investigated in this research both analytically and numerically. Electrospraying is the process during which particles of sizes in the nanometre range are simultaneously generated and charged by means of an applied electrostatic field. A high electrostatic potential is applied to a conductive capillary needle, which overcomes the force exerted by the liquid surface tension. One of the primary limitations of this process are corona discharges. The effect of corona discharges have not been studied quantitatively, even though it is frequently reported in the electrospraying literature. The main objective of this research was to understand the corona discharge thresholds associated with electrospraying. Previously, only one theoretical, and two empirical investigations studied this phenomenon, over a time period of approximately forty years. It was clear that by better understanding these thresholds, electrospraying could be applied much more effectively. A corona discharge threshold model is proposed, using either a numerical or analytical model for the calculation of polarization fields. When compared with the experimental results of other researchers, both these two models have average relative percentage errors of approximately 15%. These are the first models proposed in the literature for the calculation of electrospraying corona thresholds. A new method to determine surface tension using electrospraying is described theoretically. In addition to this method, the calculation of corona discharge thresholds have various applications. For example, the dynamics of electrostatic ion thrusters are much better described, powder production by means of electrospraying can be optimised, and pattern generation using pulsed electrospraying cone-jets can be optimised as well.
AFRIKAANSE OPSOMMING: Die elektrodinamika van arbitrêre, punt-tot-vlak elektrosproei geometrieë was beide analities en numeries ondersoek in hierdie tesis. Dit is die proses waartydens nanodeeltjies gelyktydig gegenereer en elektrostaties gelaai word. Deur 'n hoë elektriese potensiaal aan te lê tot 'n geleidende kapillêr, is dit moontlik om die krag van die oppervlakte spanning te oorkom. Een van die primêre beperkings van elektrosproei is corona ontladings. Die effek van corona ontladings was nog nie kwantitatief bestudeer nie, selfs al word dit dikwels rapporteer in die elektrosproei literatuur. Die primêre doel van hierdie navorsing was om die corona ontlading drempels te verstaan wat geassosieer word met elektrosproei. In die verlede was daar nog net een teoretiese, en twee empiriese ondersoeke gewees wat hierdie verskynsel bestuur het, oor 'n tydperk van ongeveer veertig jaar. Dit was duidelik dat deur 'n beter begrip te hê van hierdie elektrosproei drempels, kan hierdie proses baie meer doeltreffend toegepas word. In hierdie tesis word 'n corona ontlading drempel model voorgestel, wat gebruik maak van 'n analitiese of numeriese model om die polarisasie velde te bereken. Wanneer vergelyk met die resultate van ander navorsers, het beide die modelle 'n gemiddelde relatiewe persentasie fout van ongeveer 15%. Hierdie is die eerste modelle wat voorgestel word vir die berekening van corona ontlading drempels. Deur gebruik te maak van elektrosproei, word 'n nuwe metode ook voorgestel om die oppervlakte spanning te bereken. In byvoeging tot hierdie, het die berekening van corona ontlading drempels vele ander toepassings. As 'n voorbeeld, die dinamika van elektrostatiese ioon stuwers word beter beskryf, en poeier produksie deur middel van elektrosproei kan optimeer word.

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20

Privé, Michel. "Approches physiques et numérique du phénomène des vibrations induites par effet de couronne /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1986. http://theses.uqac.ca.

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Potvin, Carl. "Comportement et effet de la charge d'espace sur le mécanisme des vibrations induites par effet de couronne /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2000. http://theses.uqac.ca.

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22

Yuen, Albert Wai Ling Materials Science &amp Engineering Faculty of Science UNSW. "Collector current density and dust collection in wire-plate electrostatic precipitators." Awarded by:University of New South Wales. Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/28274.

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Even minimal improvements in particle collection efficiency of electrostatic precipitators significantly reduce dust emission from fossil-fuelled power stations and reduce pollution. Yet current designs rely on the Deutsch collection theory, which was developed for tubular precipitators and has been applied to wire-plate precipitators on the assumption that the inter-electrode electric fields at the same discharge distance in both were similar. Differences in geometry and associated collector electric fields and current density non-uniformity have not been taken into account, although the collector electric field and current density of the wire-plate precipitator are not uniform. And observations show that precipitated dust patterns and the distribution of collector current density are interrelated. Investigations revealed a simple square law relationship between the collector electric field and the collector current density in the space charge dominated coronas. Applying this relationship to the Deutsch collection theory led to a current-density-based collection formula that takes into account the non-uniform collector current density distribution. The current-density-based collection formula is then used to assess the impact of collector current density on collection efficiency, the results closely following published measurements. Applying the current-density-based collection formula to estimate the dust accumulation shows that most of the dust accumulates at collector locations facing the corona wires. The effect of the non-uniform precipitated dust layer on collection performance is assessed using the distributed corona impedance - the ratio of the inter-electrode voltage and the non-uniform collector current. Re-distribution of the collector current profile as dust builds up is also compatible with published measurements. Finally this is applied to optimize the wire-plate precipitator collection performance. This shows that optimal collection performance is obtained with the wire-wire spacing less than the wire-plate distance, once again confirming published experimental results. This is the first analytical approach to show better collection performance can be achieved at the ratio of wire-wire spacing/wire-plate distance not equal to unity, which has been the standard industry practice since 1960.

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23

Hamel, Myriam. "Influence de la variation de la température ambiante sur les vibrations induites par effet de couronne /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1991. http://theses.uqac.ca.

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24

Derakhshanian, Mahin. "Simulations numériques des vibrations induites par effet de couronne sur un court conducteur soumis à une pluie artificielle /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2001. http://theses.uqac.ca.

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Soula, Serge. "Influence de l'effet couronne sur le champ electrique mesure au voisinage du sol sous orage." Toulouse 3, 1986. http://www.theses.fr/1986TOU30213.

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Generalites sur l'electricite des orages. Mise au point d'un appareil de type gardien pour mesurer la densite ionique. Resultats experimentaux obtenus durant deux campagnes: ils concernent d'une part les mesures de champ electrique a plusieurs hauteurs dans les domaines des variations lentes et rapides, d'autre part celles de la densite ionique. Theorie du courant de maxwell sour l'orage. Simulation de l'evolution des divers parametres electriques venant confirmer les resultats experimentaux.

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26

Li, Ya. "Contribution à l'étude de l'influence des décharges de couronne sur la perte de volume d'une aspérité de glace portée à un potentiel élevé /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.

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Ndiaye, Ibrahima. "Initiation et développement des décharges couronnes sur une surface de glace /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.

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Langat, Philip Kibet. "Power-line sparking noise characterisation in the SKA environment." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17970.

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Thesis (PhD)--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: The Square Kilometre Array (SKA) and its demonstrator MeerKAT are being designed to operate over a wide frequency range and are expected to achieve greater sensitivity and resolution than existing telescopes. The radio astronomy community is well aware of the negative impact that radio frequency interference (RFI) has on observations in the proposed frequency band. This is because weak radio signals such as those from pulsars and distant galaxies are difficult to detect on their own. The presence of RFI sources in the telescope’s operating area can severely corrupt observation data, leading to inaccurate or misleading results. Power-line interference and radiation from electric fences are examples of RFI sources. Mitigation techniques for these interference sources in the SKA system’s electromagnetic environment are essential to ensure the success of this project. These techniques can be achieved with appropriate understanding of the characteristics of the noise sources. Overhead power-line interference is known to be caused mainly by corona and gap-type (commonly known as sparking noise) discharges. Sparking noise is the dominant interference for the SKA. It is mainly encountered on wooden pole lines, which are usually distribution lines operated at up to 66 kV AC in the South African network. At this voltage level, the voltage gradients on the lines are insufficient to generate conductor corona. The power requirements for SKA precursors will be below this voltage level. The aim of the research in this dissertation is to evaluate the power line sparking characteristics through measurements and simulation of line radiation and propagation characteristics. An artificially made sparking noise generator, which is mounted on a power line, is used as noise source and the radiation characteristics are measured. Measurements were carried out in different environments, which included a high-voltage laboratory (HV-Lab), a 40m test-line, and another 22-kV test line of approximately 1.5 km. The key sparking noise parameters of interest were the temporal and spectral characteristics. The time domain features considered were the pulse shape and the repetition rate. The lateral, longitudinal and height attenuation profiles were also quantified. Since sparking noise current pulses are injected or induced onto power line conductors, the line will act as an unintentional antenna. The far-field radiation characteristics of the line were evaluated through measurements on physical scale-model structures and simulations. 1/120th and 1/200th scaled lines, using an absorbing material and metallic ground planes, respectively, were simulated in FEKO. The measurements of the constructed scale models were taken in the anechoic chamber. Both measurements and simulations showed that the line exhibits an end-fire antenna pattern mode. Line length, pulse injection point and line configuration were some of the parameters found to affect the radiation patterns. The findings from this study are used to determine techniques to identify the sparking noise, and locate and correct the sources when they occur on the line hardware. Appropriate equipment is recommended to be used for the location and correction of sparking noise.
AFRIKAANSE OPSOMMING: Die Vierkante Kilometer Reeks (SKA) en sy demonstrasie projek, die Karoo Reeks Teleskoop (KAT), word ontwerp om oor 'n wye frekwensie-bereik te funksioneer. Beide sal na verwagting beter sensitiwiteit en resolusie as bestaande radioteleskope he. Die radio-astronomie-gemeenskap is deeglik bewus van die negatiewe impak wat radio-frekwensie steurnisse (RFS) op waarnemings in die voorgestelde frekwensieband het. Die rede hiervoor is dat swak radio-seine soos die van pulsars en verafgelee sterrestelsels inherent moeilik is om te bepaal. Die teenwoordigheid van RFS bronne in die teleskoop se onmiddellike operasionele gebied kan waarnemings nadelig beinvloed. Dit lei uiteindelik tot onakkurate of misleidende resultate. Kraglyne en uitstralings van elektriese heinings is voorbeelde van RFS bronne. Metodes om die oorsake van die steurnisse van die SKA se elektromagnetiese omgewing te verminder is noodsaaklik om die sukses van hierdie projekt te verseker. Dit vereis egter deeglike begrip van die eienskappe van hierdie bronne. Steurnisse as gevolg van oorhoofse kraglyne word hoofsaaklik veroorsaak deur korona en gapingtipe ontladings (algemeen bekend as vonkontladings). Vonkontladings word hier beskou as die belangrikste oorsaak van steurnisse vir die SKA. Dit word in die Suid-Afrikaanse netwerk hoofsaaklik aangetref op houtpaal-installasies, wat gewoonlik bestaan uit distribusie lyne wat tot en met 66 kV wisselstroom (WS) bedryf word. By hierdie operasionele spanning is die spanningsgradient op die lyn onvoldoende om korona op te wek. Die kragvereistes vir die SKA se voorafgaande projekte sal sodanig wees dat hierdie spanningsvlak nie oorskry sal word nie. Die doel van die navorsing omskryf in hierdie proefskrif is om die eienskappe van vonkontladings rondom kraglyne te evalueer. Dit word gedoen met behulp van metings en simulasies van uitstralings- en voortplantingspatrone wat met 'n spesifieke lyn geassosieer kan word. 'n Kunsmatige vonkontladingsopwekker word op 'n kraglyn geplaas en dien as bron om die uitstralingspatrone te meet. Metings is uitgevoer in verskillende omgewings, insluitende 'n hoogspanningslaboratorium (HV-Lab), 'n 40 m toetslyn en 'n 22 kV WS toetslyn van ongeveer 1.5 km lank. Die hoof vonkontladings eienskappe van belang is die temporale en spektrale eienskappe. Die tydgebiedeienskappe wat ondersoek is, is die pulsvorm asook die pulsherhalingskoers. Die laterale, longitudinale en hoogte-attenuasie profiele word ook gekwantifiseer. Aangesien stroompulse deur vonkontladings op die kraglyn geplaas of geinduseer word, sal die lyn as 'n ongewenste antenna optree. Die ver-veld uitstralingskenmerke van die lyn is ook geëvalueer deur gebruik te maak van fisiese skaalmodelstrukture en -simulasies. 1/120ste en 1/200ste geskaleerde lynmodelle, wat onderskeidelik 'n absorberende- en metaalgrondvlak bevat, was gebruik om 'n 3 spanlengte kraglyn te simuleer met behulp van FEKO. Metings van die fisiese skaalmodel strukture is in 'n anegoise kamer geneem. Beide die metings en die simulasies toon dat die lyn 'n endpunt uitstralingspatroon het. Lynlengte, die opwekkingsposisie van die stroompuls en die lynkonfigurasie is 'n paar van die parameters wat die uitstralingpatroon beïnvloed, soos in die navorsing aangedui. Die bevindinge van hierdie studie word gebruik om steurnisse as gevolg van vonkontladings op die kraglyn te identifiseer, op te spoor en uiteindelik reg te stel. Toepaslike toerusting word voorgestel wat gebruik kan word vir die identifisering en opsporing van vonkontladings.

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29

Demers, Pierre. "Simulation numerique des vibrations induites par effet de couronne sur les conducteurs a haute tension." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1994. http://theses.uqac.ca.

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30

Bhutt, Sanjeev. "An investigation into methods of modelling positive inhomogeneous-field breakdown and discharge process in SF6 with emphasis on the corona stabilisation phenomenon." Thesis, 2016. http://hdl.handle.net/10539/20685.

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dissertatic,11 submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering, I.: Johannesburg, 1998
Corona stabilisation is not a well understood phenomenon, consequently a rigorous theoretical description of how the merhanism operates does not exist. Furthermore, postulates on the prcJ'.tse physical processes that occur during corona stabilised breakdown are varied and conflicting. 1t was thus essential to develop a qualitative theory of how the mechanism operates around which a quantitative model could be constructed. To this aim, a detailed analysis of available modelling methods and empirical data from published works was carried out. This analysis together with additional finite elements modelling done as part of this work, leads to a proposed qualitative model which serves as a basis for a quantitative model developed to simulate corona stabilized breakdown from a fixed panicle defect. There is a favorable comparison between the predictions of the model and published measurements, thus imbuing optimism in the proposed method. The problem of measuring t: .;true charge deployed in a discharge is discussed and an experiment is designed to circumvent this problem.

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31

Pokaha, Marius Tchonang. "Modeling of the corona ionization space propulsion system." Thesis, 2011. http://hdl.handle.net/10539/10493.

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MSc., Faculty of Science, University of the Witwatersrand, 2011
In this thesis, a novel type of electrostatic thruster is introduced. The Corona Ionization (CorIon) Space Propulsion system is an electrostatic propulsion system intended for use on satellites and for deep space probes. It makes use of the corona ionization mechanism to create the needed propellant ions. This same mechanism is also responsible for the thrust, thereby reducing its size and complexity. First, the effects of incomplete ionization of propellant molecules is discussed and conclusions drawn. Next, a mathematical model describing the electric field characteristics is derived. Considering the needle tip as a point charge and the exhaust plume to be cylindrically symmetric with a constant spread angle, the resultant electric field of both the needle tip and the produced ions obeys Poisson‘s equation. The charge density is obtained from the relationship between the drift velocity and the current. In order to solve the differential equation, we consider the electric field to only change in the radial direction so that Poisson‘s Equation is reduced to its radial part. This differential equation is solved to yield the electric field of the system. Some results are discussed. By integrating the electric field the relationship between the potential difference and the current of propellant ions is obtained. This relationship also yields insight into the ionization efficiency. Following this, an expression for the thrust is derived via two different methods: The first uses the energy conservation, and is termed ―Vector heating‖. The ions are viewed as a current heating the neutrals in the plume in the direction away from the needle. A temperature can be derived for the plume, and the resulting average gas velocity estimated from molecular theory. Finally, using the rocket thrust equation, an expression for the thrust is obtained. iv The second, more conventional method uses electrostatic repulsion to calculate the recoil on the needle: from the electric field computed for the system, an expression for the Coulomb forces on the ionized propellant can be derived. The recoil on the needle will experience the same force, resulting in thrust. Finally, the theoretical predictions for the various parameters are compared to experimental data. From this comparison, it is seen that there is a reasonable agreement between the experimental data and the model even though the electrostatic prediction underestimates the thrust of the system.

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32

Engelbrecht, Michael Sean. "Relationship between corona power loss and audible noise." Thesis, 1997. http://hdl.handle.net/10539/22721.

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A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1997.
Results are reported on an initial investigation into corona power loss and its relationship to corona initiated audible noise. The work has the goal of being able to accurately predict the corona power loss, from a transmission line, from knowledge of the audible noise on the line. Corona power loss and its relationship to corona current, applied voltage and electric field is also exarr-ined. Experiments were performed using two single phase, different diameter, corona cages. Although the corona cage test results showed no correlation between corona initiated broad band audible noise and corona power loss, a linear empirical relationship, with excellent correlation, was found to exist between corona power loss and 100Hz Hum (dBA above 20jlPa). Results showed that, at the same magnitude of electric field, within the l h o different diameter corona cages, the corona current is the same magnitude and the corona power loss is proportional to the applied voltage.
MT2017

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33

Lekganyane, Mokwape Johannah. "A study of HVDC transmission line audible noise and corona loss in an indoor corona cage." Thesis, 2007. http://hdl.handle.net/10413/2193.

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The main objective of this research was to study DC conductor corona loss (CL) and audible noise (AN) in the context of local climatic conditions, through corona cage measurements, and do a comparative analysis of the measured data with results available in literature and EPRI TLW software simulation results. The ultimate aim was to assess the applicability of the software to our local conditions and hence determine, if necessary, appropriate correction factors for application in HYDC transmission line designs. For this study, short term measurements of corona AN and currents were carried out in an indoor meshed cylindrical corona cage, under DC and AC voltages. The cage was later converted into a short test line and some of the measurements repeated. The DC supply was obtained from a two stage ±500 kV Walton-Cockroft generator. The AC voltages were obtained from a 2x 100 kV, 50 Hz, AC test transformer set. The tests were performed using single solid and stranded aluminum conductors with three different diameters (1.6 cm, 2.8 cm, and 3.5 cm). All the measurements were carried out at low altitude. A CoroCAM I camera was used to determine the corona inception gradients and to observe the corona activity at different surface gradients and under different voltages and polarities. AN measurements at different conductor surface gradients were done using the Rohde&Schwarz and the Bruel&Kjaer sound level meters. To obtain the frequency spectra, a Bruel&Kjaer octave-band filter set attached to the sound level meter was used. The measured data was corrected for both height and length effects, and then compared with simulations from the EPRI-TLW software through curve fitting. A digital micro-ammeter connected to the centre of the cage through a 560 .Q measuring resistor was used to measure the corona current. Current pulses were viewed using a digital storage oscilloscope. To verify the corona current results obtained from the cage measurements, current measurements were also done for a point-plane spark gap. The corona current data was, later on, used to evaluate the total corona power loss for DC. The results obtained from test line measurements were used to compare the CL and AN for different configurations. The effect of the space charge under DC voltages was assessed through current measurements. The measurements were done with the cage covered with an aluminum foil to trap the charge and then repeated with the cage uncovered. On the test line, the space charge effect was investigated using a high power fan blowing along the conductor, to simulate the wind factor. The results of this study have shown the characteristics of corona discharges under different system voltages. The results also give an understanding of how factors such as conductor surface conditions and size, polarity and system voltage affect CL and AN. Both CL and AN were found to increase with conductor size for the same conductor surface gradient and to be higher for stranded conductors. Positive polarity DC and AC noise levels were higher than the negative polarity levels. CL under positive polarity DC was lower than the negative polarity loss. The effects of space of space charge were noted to some extend. The comparison of test line results and cage results showed that CL depends more on the gap size and the shorter the gap the higher the loss. Hence CL results were not compared with the software simulations. The comparison between the corrected AN results and the software simulations showed a very good agreement. The comparison was done for the 3.5 cm and the 2.8 cm diameter conductors under both positive and negative polarities. The trends compared through curve fitting were quite similar and the trend line equations were of the same order of magnitude. The magnitudes of the corrected noise levels were higher than the CRIEPI and BPA predictions but closer to the EPRl prediction. Generally there is a very good and encouraging agreement between the available literature, simulation results and the results obtained from the laboratory measurements. It is proposed, as part of further studies, to extend this work to high altitude regions and use bundled conductors as well. Consideration of different and larger test configurations will provide an understanding of the effects of geometry on corona discharges. Space charge analysis will also assist in determining the effect of space charge on different configurations.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

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34

Krommenhoek, Marinus Frans. "Modelling of the propulsion mechanism for a miniaturized corona ionization thruster." Thesis, 2015. http://hdl.handle.net/10539/20450.

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A dissertation submitted to the Faculty of Science, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science.
In this dissertation a recipe has been outlined on how thrust can be calculated using the conservation of momentum in continuum form. With the aim of modelling a CORION (corona ionization) like thruster in mind it was then argued using a much simpler system and stochastic calculus why a statistical description of the system is necessary. From this the one-particle distribution emerged as a natural tool for the description of a system su cient for the determination of the system's thrust.This was followed by a short investigation into the background of non-equilibrium statistical mechanics, both classical and quantum, necessary to understand how one-particle distributions could be derived formally and in a physically consistent way. Mass ow and current-voltage experiments of the CORION like thrust system, necessary for characterization of part of the system, were conducted. This led to a proposal for a modelling strategy, consisting of merging di erent modelling approaches and descriptions considered throughout the dissertation.

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Xiao, Fuchun. "Electrostatic charging of water sprays by corona and induction for dust suppression /." 2000. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040708.143251/index.html.

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36

Bussy, Eamon Riccardo. "Effect of ADLash opitical fibre cable on corona onset gradient and electric fields around the shield wire of the Apollo-Cahora Bassa HVDC line." Thesis, 2005. http://hdl.handle.net/10413/2686.

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Abstract:

ADLash® is the trade name for an optical fibre cable attached to a transmission line shield wire using aramid-reinforced bands. The installation of this type of optic fibre cable has been considered for the HVDC line from the Songo hydroelectric scheme at Cahora Bassa in Mozambique, to Apollo substation in South Africa. The impact that installation of this cable will have on the onset of corona is examined. The shield wire with and without ADLash attached is modelled for both the actual line configuration and for corona cage studies. The electric field is calculated using the Method of Images and the Boundary Element Method to predict the electric field enhancements and to estimate the corona onset gradient. Corona onset gradients and phenomena for smooth and stranded conductors are researched to aid the prediction of voltage onset magnitudes for the corona cage. Estimated values are compared with observed values for both AC and DC applied voltages. Different patterns of corona and different corona onset voltages are observed for AC and negative DC applied voltages. The relative permittivity of the ADLash is higher than the surrounding air and this is shown to lead to greatly enhanced electric fields at the air/ dielectric/ shield wire interfaces that are significant enough to cause corona at the rated operating voltage. The corona will bombard the ADLash and probably damage it. Some alternative methods of installing fibre optic cables are reviewed for further research because the use of ADLash cannot be recommended.
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

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37

"Experimental studies on electrical and lift-force models of the ionic flyer with wire-plate electrode configuration." 2007. http://library.cuhk.edu.hk/record=b5893487.

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Abstract:

Chung, Chor Fung.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 95-97).
Abstracts in English and Chinese.
Acknowledgements --- p.iv
Table of Contents --- p.v
List of Figures --- p.viii
List of Tables --- p.xiii
Nomenclature --- p.xiv
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Development of Micro Indoor Surveillance Flyers --- p.1
Chapter 1.1.1 --- Overview --- p.1
Chapter 1.1.2 --- Intrinsic Problem of Surveillance Helicopters --- p.2
Chapter 1.2 --- Proposed Non-moving Parts and Noiseless Flyers --- p.2
Chapter 1.3 --- Organization of the remaining dissertation --- p.5
Chapter Chapter 2 --- The Basic Structure of the Ionic Flyers --- p.7
Chapter 2.1 --- The Components and the Structural Parameters of the Ionic Flyers --- p.7
Chapter 2.2 --- Proposed Operational Principles --- p.8
Chapter 2.2.1 --- The Electrohydrodynamic Effect --- p.9
Chapter 2.2.2 --- The Biefeld-Brown Effect --- p.10
Chapter Chapter 3 --- Overview of Corona Discharge --- p.11
Chapter 3.1 --- The Gaseous Discharge --- p.11
Chapter 3.2 --- "Uniform Fields, Electrical Breakdown" --- p.12
Chapter 3.3 --- "Non-uniform Fields, Corona Discharge" --- p.12
Chapter 3.3.1 --- Positive Corona Discharge --- p.13
Chapter 3.3.2 --- Negative Corona Discharge --- p.14
Chapter 3.4 --- Conclusion --- p.15
Chapter Chapter 4 --- Electrical Current-Voltage Model --- p.16
Chapter 4.1 --- Experimental Setup and Measurement --- p.17
Chapter 4.2 --- Basic Current to Voltage Relationship --- p.18
Chapter 4.2.1 --- The Three Electrical Stages of the Ionic Flyers --- p.20
Chapter 4.2.2 --- Proposed Quadratic Equation for the Current to Voltage Relationship --- p.22
Chapter 4.3 --- Determination of the Current Gain C and the Onset Voltage V0 by the Structural Parameters of the Ionic Flyers --- p.22
Chapter 4.3.1 --- The Electrode Length (L) --- p.24
Chapter 4.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.27
Chapter 4.3.3 --- The Wire-emitter Radius (rw) --- p.31
Chapter 4.3.4 --- The Plate-collector Height (h) --- p.36
Chapter 4.3.5 --- The Electrode Enclosed Area (A) --- p.38
Chapter 4.3.6 --- The Electrical Environmental Constant (Ke) --- p.43
Chapter 4.4 --- Summary of the Experimental Derived Current-Voltage Model --- p.45
Chapter Chapter 5 --- Mechanical Lift-force Models --- p.46
Chapter 5.1 --- Experimental Setup and Measurement --- p.47
Chapter 5.2 --- Basic Lift-force to Voltage Relationship --- p.49
Chapter 5.2.1 --- The Initial Power Dissipation (IPD) --- p.50
Chapter 5.2.2 --- The Maximum Lift-force --- p.51
Chapter 5.2.3 --- Proposed Third-order Equation for the Lift-force to Power Relationship --- p.52
Chapter 5.3 --- Determination of the Voltage Gain J and the Barrier Voltage Vfby the Structural Parameters of the Ionic Flyers --- p.54
Chapter 5.3.1 --- The Electrical Length (L) --- p.55
Chapter 5.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.59
Chapter 5.3.3 --- The Wire-emitter Radius (rw) --- p.63
Chapter 5.3.4 --- The Plate-collector Height (h) --- p.66
Chapter 5.3.5 --- The Electrode Enclosed Area (A) --- p.67
Chapter 5.3.6 --- The Lift-force Environmental Constant (Kf) --- p.71
Chapter 5.4 --- Summary of the Experimental Derived Lift-force Model --- p.73
Chapter 5.5 --- Analysis on the Force/Power Ratio of the Ionic Flyers --- p.74
Chapter Chapter 6 --- Further development of the Ionic Flyers --- p.76
Chapter 6.1 --- Multi-directional Force Generation --- p.76
Chapter 6.1.1 --- Linear Motion --- p.77
Chapter 6.1.2 --- Rotation Motion --- p.78
Chapter 6.2 --- Application of MEMS Motion Sensors and Wireless Signal Transmission --- p.80
Chapter Chapter 7 --- Future Work --- p.84
Chapter 7.1 --- Single-Emitter-Multiple-Collector Ionic Flyers --- p.84
Chapter 7.2 --- Development of Miniaturized High-voltage Power Supply --- p.88
Chapter Chapter 8 --- Conclusion --- p.90
Chapter 8.1 --- The Electrical Current to Voltage Model --- p.90
Chapter 8.2 --- The Mechanical Lift-force to Power Model --- p.91
Chapter 8.3 --- The Force/Power Ratio Model --- p.91
Appendix A --- p.92

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38

Chatterjee, Sreenita. "Dimensioning Of Corona Control Rings For EHV/UHV Line Hardware And Substations." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2446.

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Abstract:

High voltage (EHV and UHV) transmission facilitates transfer of large amount of power over long distances. However, due to the inherent geometry, the line and substation hardware of EHV and UHV class generate high electric fields, which results in local ionisation of air called corona discharges. Apart from producing audible noise in the form of frying or hissing sound, corona produces significant electromagnetic interferences in the radio range. The limit for this corona generated Radio Interference (RI) has been stipulated by international standards, which are strictly to be followed. In line and substation hardware, corona control rings are generally employed to limit or avoid corona. Standard dimensions of corona rings are not available for EHV and UHV class. In most of the cases, their design is based on either a trial and error method or based on empirical extrapolation. Only in certain specific cases, the dimensioning of the rings is carried out using electric field calculations. In any of these approaches, the unavoidable surface abrasions, which can lead to corona, are not considered. There are also efforts to account for nominal surface irregularity by using a surface roughness factor, which is highly heuristic. In order to address this practically relevant problem, the present work was taken up. The intended exercise requires accurate field computation and a suitable criterion for checking corona onset. For the first part, the Surface Charge Simulation Method is adopted with newly proposed sub-modelling technique. The surface of the toroid is discretised into curvilinear patches with linear approximation for the surface charge density. Owing to its high accuracy, Galerkin’s method of moments formulation is employed. The problem of singularity encountered in the numerical approach is handled using a method based on Duffy’s transformation. The developed codes have also been validated with standard geometries. After a survey of relevant literature the ‘Critical Avalanche Criteria’ is chosen for its simplicity and applicability to the problem. Through a detailed simulation, the effect of avalanche space charge in reducing the corona onset voltage is found to be around 1.5% and hence it is not considered further. For utilities not interested in a detailed calculation procedure for dimensioning of corona rings, design curves are developed for circular corona rings of both 400 kV and 765 kV class with surface roughness factor in the range 0.8 – 1. In the second part of the work, a methodology for dimensioning is developed wherein the inevitable surface abrasion in the form of minute protrusions can be accounted. It is first shown that even though considerable field intensification occurs at the protrusions, such localised modification need not lead to corona. It is shown that by varying the minor radius of the corona ring, it is possible to get a design where the prescribed surface abrasion does not lead to corona onset. In summary, the present work has successfully developed a reliable methodology for the design of corona rings with prescribed surface abrasions. It involved development of an efficient field computation technique for handling minute surface protrusions and use of appropriate criteria for assessing corona inception. It has also provided design curves for EHV and UHV class corona rings with surface roughness factor specified in the range 0.8 – 1.0.

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39

Chatterjee, Sreenita. "Dimensioning Of Corona Control Rings For EHV/UHV Line Hardware And Substations." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2446.

Full text

Abstract:

High voltage (EHV and UHV) transmission facilitates transfer of large amount of power over long distances. However, due to the inherent geometry, the line and substation hardware of EHV and UHV class generate high electric fields, which results in local ionisation of air called corona discharges. Apart from producing audible noise in the form of frying or hissing sound, corona produces significant electromagnetic interferences in the radio range. The limit for this corona generated Radio Interference (RI) has been stipulated by international standards, which are strictly to be followed. In line and substation hardware, corona control rings are generally employed to limit or avoid corona. Standard dimensions of corona rings are not available for EHV and UHV class. In most of the cases, their design is based on either a trial and error method or based on empirical extrapolation. Only in certain specific cases, the dimensioning of the rings is carried out using electric field calculations. In any of these approaches, the unavoidable surface abrasions, which can lead to corona, are not considered. There are also efforts to account for nominal surface irregularity by using a surface roughness factor, which is highly heuristic. In order to address this practically relevant problem, the present work was taken up. The intended exercise requires accurate field computation and a suitable criterion for checking corona onset. For the first part, the Surface Charge Simulation Method is adopted with newly proposed sub-modelling technique. The surface of the toroid is discretised into curvilinear patches with linear approximation for the surface charge density. Owing to its high accuracy, Galerkin’s method of moments formulation is employed. The problem of singularity encountered in the numerical approach is handled using a method based on Duffy’s transformation. The developed codes have also been validated with standard geometries. After a survey of relevant literature the ‘Critical Avalanche Criteria’ is chosen for its simplicity and applicability to the problem. Through a detailed simulation, the effect of avalanche space charge in reducing the corona onset voltage is found to be around 1.5% and hence it is not considered further. For utilities not interested in a detailed calculation procedure for dimensioning of corona rings, design curves are developed for circular corona rings of both 400 kV and 765 kV class with surface roughness factor in the range 0.8 – 1. In the second part of the work, a methodology for dimensioning is developed wherein the inevitable surface abrasion in the form of minute protrusions can be accounted. It is first shown that even though considerable field intensification occurs at the protrusions, such localised modification need not lead to corona. It is shown that by varying the minor radius of the corona ring, it is possible to get a design where the prescribed surface abrasion does not lead to corona onset. In summary, the present work has successfully developed a reliable methodology for the design of corona rings with prescribed surface abrasions. It involved development of an efficient field computation technique for handling minute surface protrusions and use of appropriate criteria for assessing corona inception. It has also provided design curves for EHV and UHV class corona rings with surface roughness factor specified in the range 0.8 – 1.0.

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