Orientador: João Sinézio de Carvalho Campos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T20:46:43Z (GMT). No. of bitstreams: 1 Lopes_SelmaAparecida_M.pdf: 4679717 bytes, checksum: b44b60b38798f2147b5fd6fe7eacc78f (MD5) Previous issue date: 2012 / 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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Ozone generation is a problem associated with indoor air cleaners that utilize a corona to ionize particles. This experimentation utilized a negative corona and investigated the effect that external electrode wire heating had on the ozone production rate. Results showed that the ozone generation rate could be significantly reduced by raising the electrode surface temperature to 85 °C. Above this temperature, no further ozone reduction was observed. A linear relationship existed between ozone concentration and corona current. A parabolic relationship existed between corona current and corona voltage potential. Smaller corona wire diameters produced ozone at lower rates than larger corona wire diameters. A description of the investigation, the data collected, and a discussion of all results is included. / Master of Science

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.

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

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.

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.

Thesis (Ph. D.)--University of New South Wales, 2000. / Also available (in part) online.

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