Dissertations / Theses on the topic 'High voltage electrical discharge (HVED)'

L'objectif principal de la thèse est de développer une technologie efficace pour la dégradation des pesticides. L'herbicide atrazine a été étudié comme molécule modèle. L'atrazine a été dégradée dans l'eau par décharge électrique de haute tension (DEHT), et ses performances de dégradation ont été comparées aux technologies traditionnelles d'oxydation de Fenton et d'ultrasons (US). La détection et la quantification de l'atrazine et de ses métabolites ont été réalisées par chromatographie liquide haute performance et spectrométrie de masse à haute résolution (HPLC-HRMS). Une méthode d'analyse en ligne par HPLC-HRMS combinée à un échantillonnage automatique a été développée pour un suivi en temps réel du processus de dégradation. La technologie DEHT a dégradé efficacement l'atrazine et a réduit les métabolites toxiques générés au cours des processus d’oxydation de Fenton et d’US. Le procédé de DEHT est moins consommateur d'énergie que le procédé d’US tout en atteignant la même efficacité de dégradation de l'atrazine de 89%. Les mécanismes de dégradation de l'atrazine pour les différentes technologies ont été proposés. L'effet d'une matrice réelle (eau du robinet) par rapport à une matrice modèle (eau déminéralisée) sur la dégradation de l'atrazine a été étudié. Les résultats ont montré que dans le cas d’un traitement par DEHT, l'efficacité de dégradation de l'atrazine dans l'eau du robinet était inférieure à celle de l'eau déminéralisée, ce qui peut être lié à la conductivité de l'eau et au mécanisme de génération des arcs électriques dans un milieu conducteur. La toxicité aiguë (CL50) chez la daphnie Daphnia magna a été utilisée pour évaluer la toxicité des différentes solutions de traitement contenant initialement de l'atrazine. La toxicité de la solution d'atrazine traitée par oxydation de Fenton est supérieure à celle traitée par DEHT et US
The main goal of this thesis is to develop an efficient technology for the degradation of pesticides. For this purpose, the widely used herbicide atrazine was studied as a model molecule. Atrazine was degraded in water by high voltage electrical discharge (HVED), and its degradation performance was compared with traditional water treatment technologies Fenton oxidation and ultrasound (US). The detection and quantification of atrazine and its metabolites were achieved by high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). An online analysis method by HPLC-HRMS combined with automatic sampling was developed for real-time monitoring of the degradation process. The HVED technology efficiently degraded atrazine and reduced toxic metabolites generated during Fenton oxidation and US processes. HVED process has less energy consumption than US process while achieving the same 89% atrazine degradation efficiency. The mechanism pathways of atrazine degradation for different technologies were proposed. The effect of real matrix (tap water) versus model matrix (deionized water) on atrazine degradation was studied. Results showed that in HVED treatment, the degradation efficiency of atrazine in tap water was lower than that in deionized water, which may be related to the conductivity of the water and to the mechanism of electric arcs generation in a conductive medium. The acute toxicity (LC50) in Daphnia magna was used to evaluate the toxicity of different treatment solutions initially containing atrazine. The toxicity of atrazine solution treated by Fenton oxidation is higher than that treated by HVED and US

Ce travail de recherche se concentre sur l'extraction et le fractionnement des biomolécules à partir de microalgues par des traitements physiques: les champs électriques pulsés (CEP), les décharges électriques de hautes tensions (DEHT) et les ultrasons (US). Dans cette étude, trois espèces de microalgues Nannochloropsis sp., Phaeodactylum tricornutum (P. tricornutum) et Parachlorella kessleri (P. kessleri) ont été étudiées. Les espèces ont différentes formes cellulaires, structure et contenu intracellulaire. L'effet des techniques testées sur l'extraction des biomolécules a été mis en évidence à travers une analyse quantitative et qualitative: suivi du rendement des composés ioniques, des glucides, des protéines, des pigments et des lipides. Une étude comparative des traitements physiques (CEP, DEHT et US), à la même énergie, pour la libération des biomolécules intracellulaires à partir des trois espèces de microalgues, a permis de mieux comprendre les différents mécanismes de désintégration. Pour chaque microalgue, à la même énergie consommée, le traitement par DEHT s'est révélé le plus efficace en terme d'extraction des glucides, tandis que les US sont plus efficaces pour l'extraction des protéines et des pigments. Le traitement par CEP a été moins efficace en terme du rendement d’extraction. Cependant, la meilleure sélectivité (extraction des glucides) a été obtenue en utilisant les CEP ou les DEHT. Les prétraitements physiques (CEP, DEHT ou US) des suspensions plus concentrées suivis d'une homogénéisation haute pression (HHP) de suspensions diluées ont permis d'améliorer l'efficacité de l'extraction et de diminuer la consommation énergétique totale et le nombre de passages. Le prétraitement physique permet de réduire la pression mécanique de l’HHP, pour atteindre le même rendement d’extraction. Pour la valorisation maximale de la biomasse de microalgues, une procédure d'extraction assistée par DEHT (40 kV/cm, 1-8 ms) suivie de plusieurs étapes d'extraction aqueuses et non aqueuses semble être utile pour l'extraction sélective et le fractionnement de différentes biomolécules à partir de microalgues. Des effets significatifs du prétraitement HVED sur l'extraction par solvant organique des pigments (chlorophylles, caroténoïdes) et des lipides ont été observés
This research work focuses on extraction and fractionation of bio-molecules from microalgae using physical treatments: pulsed electric fields (PEF), high voltage electrical discharges (HVED) and ultrasonication (US) techniques. In this study, three microalgae species Nannochloropsis sp., Phaeodactylum tricornutum (P. tricornutum) and Parachlorella kessleri (P. kessleri) were investigated. These species have different cell shapes, structure and intracellular contents. The effects of tested techniques on extraction of bio-molecules have been highlighted in a quantitative and qualitative analysis by evaluating the ionic components, carbohydrates, proteins, pigments and lipids. A comparative study of physical treatments (PEF, HVED and US) at the equivalent energy input for release of intracellular bio-molecules from three microalgal species allowed us to better understand the different disintegration mechanisms. For each microalga at the same energy consumption, the HVED treatment proved to be the most efficient for extraction of carbohydrates, while the US treatment for extraction of proteins and pigments. In general, the smallest efficiency was observed for the PEF treatment. However, the highest selectivity towards carbohydrates can be obtained using the mild PEF or HVED technique. The preliminary physical treatments (PEF, HVED or US) of more concentrated suspensions followed by high pressure homogenization (HPH) of diluted suspensions allowed improving the extraction efficiency and decreasing the total energy consumption. The physical pretreatments permit to reduce the mechanical pressure of the HPH and number of passes, to reach the same extraction yield. For the maximum valorisation of microalgal biomass, extraction procedure assisted by HVED treatment (40 kV/cm, 1-8 ms) followed by aqueous and non-aqueous extraction steps seems to be useful for selective extraction and fractionation of different bio-molecules from microalgae. The significant effects of HVED pre-treatment on organic solvent extraction of pigments (chlorophylls, carotenoids) and lipids were also observed

Increased electrical power demands are being experienced on the new generation of aircraft due to an increased reliance on electrical technology of systems such as air conditioning, de-icing systems and electrical flight control actuation. Distribution of power at higher AC and DC voltages is therefore now being seen in modern aircraft to avoid the penalties incurred due to high cable weights. Voltages have increased past the minimum of Paschen's law resulting in a risk that life limiting partial discharge (PD) damage can occur in the insulation systems. This thesis uses a theoretical analysis backed by PD experimental results to investigate the optimal operating voltage of a cabling system. In addition, it proposes a methodology for optimizing the operating voltage level based on an analysis of the power carrying capability of cabling within a fixed and a non-fixed volume system and the derivation of the cable weight as a function of voltage. Furthermore the power carrying capability of a certain round cable system is compared with an insulated flat conductor system as in a printed circuit board (PCB). An initial assessment has been carried out to determine whether more power can be delivered via insulated flat solid conductors as in a PCB, instead of using round cables. The reason why there is a need to investigate this aspect, is because using new PCB technology can offer several advantages over traditional cabling harnesses. The work done has shown that the optimal operating point (e.g. maximum power to weight ratio) for an aircraft power system, does not improve after certain voltage levels. A tradeoff between cable weight and power transfer is required and furthermore the use of DC systems can result in higher power transfers than conventional three phase/400Hz AC systems. The PCB maximum power transfer assessment has also shown that insulated flat conductor systems can offer higher power transfer efficiencies. In addition, experimental AC and DC PD tests on certain unscreened aerospace cables (laid out in different configurations), have shown that the theoretical analysis employed to determine cable safe operating voltages gives conservative results.

In this thesis work, a new partial discharge magnitude indicator with LCD display was designed. This system was implemented in high voltage partial discharge detection and measurement systems. AVRISP In-System programmer is used to program the microprocessors used inside the display unit. The time resolution of the system (one pixel of the display unit) is 4 microseconds. The unit is capable of counting the number of impulses of the input voltage that is coming from the high voltage system within user selectable time intervals. The changeable values of the time intervals are 2, 4, 6, 8 and 10 seconds. It is also capable of showing the maximum value of the impulses in a given time interval. This maximum value is a number changing between 0 and 256. By calibration of the system, it was possible to indicate the discharge magnitudes in picocoulombs.

This thesis is concerned with developing a new approach to high voltage transformers condition monitoring, which involve partial discharge (PD) measurement and localisation within high-voltage transformer windings. This is an important source of information for both diagnosis and prognosis of the health of power transformers. Generally, Partial discharges (PDs) existence in transformer windings are normally due to ageing processes, operational over stressing or defects introduced during manufacture. Although, the presence of PDs does not necessarily indicate imminent failure of a transformer, it is however, a serious insulation degradation or ageing mechanism which can be considered as a precursor of transformer failure. The initial approach taken in this thesis is based on a lumped parameter network model. The model was created and its parameters were approximated using analytical solutions based on the geometrical dimensions of transformer windings. Based on the lumped parameter network model, theoretically the rational function should be a positive-real (PR) function and it is shown later on in this thesis that the model does hold the theoretical assumptions. Nevertheless, impulse response of actual transformer windings constructed for laboratory assessment was shown differently although different methods were used to find rational functions with positive-real (PR). Due to the fact that real transformer windings do not hold the characteristic of positive real transfer function, thus, this thesis finds an alternative and proposes a different approach for PD localisation which is based on energy distribution and features extraction methods for localisation, particularly Wavelet Transform (WT) and Principal Component Analysis (PCA). The idea of the developed approach is based on the fact that any discharge occurring at any point along windings produce an electrical signal that will propagate as a travelling wave towards both ends of the windings. During the propagation of the PD signals along transformer windings, the response with respect to the propagation path taken and termination characteristics will cause attenuation and distortion to the waveforms, ultimately produced changes in the energy characteristics of the PD pulses when they reach measurement sensors.

The thesis concerns partial discharge (PD) propagation within a high voltage transformer winding. Location of PDs and magnitude estimation are important tools for both diagnosis and prognosis of the health of large transformers. In reality there is limited access and knowledge of a winding and consequently any practical method requires the use of estimation techniques. The approach taken in this thesis is by considering lumped circuit parameter models. Firstly, a lumped capacitive parameter model was considered and secondly a transmission line lumped parameter approach developed. A technique of split winding analysis is introduced for both types of model. The derivation of the capacitive network considers the source location of a PD by defining the PD signal propagation in two directions. At the source, the currents are equal in magnitude and are attenuated as they flow in each direction. This provides information for a fixed distribution model equation. Under transmission line lumped parameter models, split winding analysis explains the development of accumulated harmonic waveforms of the PD propagation signal towards the neutral and bushing tap-point. At the source, a D’Alembert solution is employed to estimate the oscillation level and found to be in very good agreement with measured data using rectangular wave signal injection. PD signal behaviour is then considered using a time varying boundary conditions model with a principle of superposition equation of source signal. Duhamel’s principle is employed to find a solution for any waveform applied to some point on the transformer winding. Under the influence of losses and distortion, an accumulated harmonic amplitude analysis from the Duhamel’s principle estimates the PD propagation level. For different injection points along the transformer winding, the measured PD level at the neutral and bushing tap point caused by the accumulated harmonic amplitude reveals different patterns. As the PD injection point is altered from the bushing tap point to the neutral, the measured signals significantly change. This in turn contains information of the level of discharge signal at the source. From this analysis a technique based on minimum mean error (MME) calculation using the measurements at the bushing tap and neutral points can be used to identify the source location of PDs based on the analysis of accumulated harmonic amplitudes. With a known location, the information can then be used to estimate PD levels. As the actual charge transferred at the location of a partial discharge cannot be measured directly, by using the D’Alembert solution, the PD source level is found to have approximately twice the apparent magnitude. By using the predominantly capacitive model derived based on split current propagation, PD estimation at higher frequencies is also possible. As a result, an estimation of PD level can be estimated for measurement signals having bandwidth of up to 150MHz.

Due to the universal considerable population and economic growth rate, demands for energy have risen significantly over the past decade. This means that the integration of renewable energies in the power grid has escalated as well as requests for reactive power compensation, voltage stability, and mitigation of harmonic filters. Capacitor banks are widely used in the modern electrical transmission system in order to improve power quality and efficiency. In other words, this device aims to be involved in harmonic disturbance elimination, improve the power factor (PF), provide voltage control and stability which leads into more sustainable energy systems. Utilizing high voltage components, such as shunt capacitors in the power grid can introduce new challenges. One of these challenges is known as corona discharge. The aim of the presented master thesis is to study and develop corona discharge suppression models on high voltage capacitor banks which is implemented in collaboration with ABB power grids, Sweden. The main concerns are, effective factors on corona emergence, corona inception voltage levels, and corona suppression methods. Also, this study evaluates the verification of existing suppression. Two various approaches were applied and compared. The aim of the first approach is to evaluate corona discharge by electric field calculations on three various capacitor banks with different voltage levels. The simulation was implemented based on Maxwell’s equations and finite element method (FEM) by utilizing COMSOL Multiphysics software. The second approach is based on streamer inception and propagation. The calculation on this method is fulfilled with the help of MATLAB software. The results of both approaches were found reasonably compatible. It is discovered that corona discharge can appear in different voltage levels on capacitor banks based on various factors, such as the geometry of the bank. Consequently, the suppression method may vary case by case and different proposals were suggested in order to optimize the corona suppression rings.
På grund av den allmänna betydande befolknings- och ekonomiska tillväxttakten har kraven på energi ökat markant under det senaste decenniet. Detta innebär att integrationen av förnybara energier i elnätet har eskalerat samt begäran om reaktiv effektkompensering, spänningsstabilitet och mildring av harmoniska filter. kondensatorbatterier används ofta i det moderna elektriska transmissionssystemet för att förbättra strömkvaliteten och effektiviteten. Med andra ord syftar denna enhet till att vara involverad i eliminering av harmonisk störning, förbättra effektfaktorn (PF), tillhandahålla spänningskontroll och stabilitet som leder till mer hållbara energisystem. Att använda högspänningskomponenter, som shuntkondensatorer i elnätet, kan skapa nya utmaningar. En av dessa utmaningar kallas korona-urladdning. Syftet med den presenterade masteruppsatsen är att studera och utveckla korona-urladdningsmodeller på högspännings-kondensatorbatterier som implementeras i samarbete med ABB Power Grids, Sverige. De viktigaste problemen är effektiva faktorer för korona uppkomst, spänningsnivåer korona och metoder för att underlätta korona. Dessutom utvärderar denna studie verifieringen av befintliga undertryckningsmetoder. Två olika tillvägagångssätt tillämpades och jämfördes. Syftet med det första tillvägagångssättet är att utvärdera korona-urladdning genom elektriska fältberäkningar på tre olika kondensatorbatterier med olika spänningsnivåer. Simuleringen implementerades baserat på Maxwells ekvationer och finita elementmetoden (FEM) genom att använda COMSOL Multiphysics programvara. Det andra tillvägagångssättet är baserat på strömningslinjernas början och utbredning. Beräkningen av denna metod genomförs med hjälp av MATLAB-programvaran. Resultaten från båda metoderna tycktes vara rimligt kompatibla. Det upptäcks att korona-urladdning kan förekomma i olika spänningsnivåer på kondensatorbatterier baserat på olika faktorer, till exempel batteriets geometri. Följaktligen kan undertryckningsmetoden variera från fall till fall och olika förslag föreslogs för att optimera koronaundertryckningsringarna.

This dissertation deals with research on the numerical modelling of electrical discharges in laboratory long air gaps excited with positive switching impulses. It begins with the preliminary work of several scientists during the last decades, making a detailed analysis of different approaches for modelling all the stages in a full discharge. The relations between these models are identified as well as the effect on the outcome when modifying some important input parameters. The general concept describing the discharge phenomenon usually includes three main elements: the streamer inception, the streamer-to-leader transition and the stable leader propagation. These elements are present in many of the analysed models and the main differences between them are the assumptions and simplifications made by each author at a specific point in their methodologies. The models are usually simplified by assigning experimentally determined values to physical constants pertinent to different stages of the full discharge. These constants are the potential gradient in the leader-corona region to sustain the leader propagation, the charge per unit length along the leader channel which depends on the atmospheric conditions and the voltage impulse wave shape; and the leader propagation velocity, which is closely related to the discharge current. The dissertation includes the results of laboratory work related the study of leaders in long gap discharges, electrical parameters and optical records. By reconstructing the three-dimensional leader propagation for the rod-to-plane configuration, it was possible to study the random tortuous path followed by the leader as it propagates. One important element included in the discharge modelling is the representation of the leader-corona region in front of the leader tip as it propagates towards the grounded electrode. For the calculation of the net charge available in the leader-corona region, two new methodologies were pro-posed based on the electrostatic potential distribution obtained from a finite element method solver. This allowed the inclusion of more elements representing different parts of the discharge in the simulation domain. In the final part, all the analysed elements and the new proposed ones were included in a new methodology for the modelling of electrical dis-charges in long air laboratory gaps. The results obtained from this methodology were compared to experimental data. A good agreement was found between the simulation results and the experimental data.

Ever since the discovery of DNA, there has been many pathologies identified effecting mankind. With the development in technology, there are many methods to alleviate these pathologies. One such is gene therapy or gene delivery. It is a process of introducing some foreign material into the body to correct the effected cells. In principle, it is a modern method to cure cells or a method to transfer nucleic acid into a cell to treat specific cells in the body. The process of delivering a genetic material is carried out using vectors, namely, viral vectors and non-viral vectors. In viral vectors, viruses are modified to make it efficient for delivery into the host cells. This method has high transduction rate as compared to non-viral method. Non-viral methods include chemical and physical transfection methods, which are used to deliver the gene of interest into the host cell unlike viral methods. In this study, a physical method using high voltage is used to deliver a genetic material into cells. High voltages are used to permeabilize the cell to allow the foreign material into it and to express it in the host cell. This process is termed as Electroporation. In specific, in this research, studying a process of charging a region that mimics skin and trying to localize the presence of electric fields on the surface where the strongest uptake of genetic material is found. In other words, region where the gene expression is strongest at a specific region if performed on skin is studied by localizing electric fields on the surfaces. My work is to characterize and develop where this effect takes place on the surface based on both positive and negative electric fields. A physical method is useful as it is a non-toxic way to get a DNA/protein into someone’s body without making them sick, unless if not using a virus to deliver. This is all done using high voltages up to 8kV and the electric fields produced due to high voltages are localized, visualized and characterized with both positive and negative polarities of voltages. In this study, experiments with high voltages are performed and the spread of charges at specific regions are collected using a needle. This needle goes into corona, which may be called as a secondary corona. It might be called a secondary corona because the flat conductor is being charged by a metal finger but not directly by the power supply. Here, the conductor is charged by a metal finger of high input voltage, which ionizes the air molecules above the flat conductor to form a conductive region. As the input voltage is increased further, electrons escape from the needle to air or from molecules to needle forming negative or positive ions respectively. The outputs at needle were measured on the oscilloscope. In this study, repeated sets of experiments are carried out to collect consistent and reliable data. Visualizing/characterizing these fields are important as maximum delivery takes place at high voltage regions, with a condition that permeability of the cells should be known for proper transfection to occur, otherwise cells would die due to high voltages or no transfection takes place due to poor permeability of cell membrane.

Electrical insulating systems represent one of the weakest elements of the entire electrical equipment. In fact, the lifetime of any electrical device depends on the capability of its insulation to last in time. In general, all organic materials, and in particular all dielectrics, are subjected to ageing. The ageing process is caused by different stresses: thermal, electrical, mechanical and environmental. By focusing on the electrical stress, it is possible to state that it is fundamentally characterized by two phenomena: the presence of an electric field and/or the presence of partial discharges (PDs), a phenomenon in which the interelectrode zone is partially short-circuited causing degradation of the material. It is clear, therefore, how partial discharges are both the symptom and the cause of the deterioration of the insulating materials. Thus, the measurement of this phenomenon leads to obtain an “image” of the status of the insulating system allowing to perform a predictive diagnostic by an expert user or by sophisticate artificial intelligence algorithms. These diagnostic techniques lead to reduce the maintenance costs since they allow to perform a condition-based maintenance that is carried out only when this is necessary, according to the real state of the component. To measure the partial discharge activity there are different methods, but it is possible to classify them into two groups: electrical detection methods and non-electrical detection methods. If the electrical methods typically need invasive procedures to perform the partial discharge measurement, the non-electrical ones, on the contrary, can be implemented on the electrical component without any change (non-invasive) in the normal operating of the equipment. The focus of this research activity is to study, develop and optimize prototypes, test them in laboratory and in real applications of different non-invasive sensors in order to measure partial discharges. Two kind of sensors are analysed: Transient Earth Voltage Sensors and High Frequency Current Transformers ones. Transient Earth Voltage Sensors are based on the homonymous operating principle, and they can be used when the electrical apparatus is placed inside a metal box like switchgears or gas insulated systems. Starting from a first investigation on the effect of the geometrical dimensions of different sensors prototype in order to maximize the signal output, a first preliminary on-field test campaign is performed on an industrial air insulated medium voltage switchgear. Then, the entire partial discharge measurement system configuration, based on a definitive version of TEV sensor, is optimized and tested on the industrial test set-up, by comparing the obtained PD pattern with those collected from an IEC 60270 standard compliant measurement system. The results suggest how the non-invasive PD measurement system provides information comparable to those collected by the standard-compliant one. The High Frequency Current Transformer Sensors are studied and optimized during an experimental laboratory activity where different magnetic core material and different sensor configurations are tested. The results allow to implement the HFCT sensor on an optimized PD measurement system introduced to perform a research investigation on the phenomenon of electrical treeing on HVDC cable insulation, carried out during an exchange program at the RWTH Aachen University in Germany. The aim of this investigation is to understand the behaviour of the electrical treeing with different voltage frequencies and amplitudes during long-term tests since some preliminary tests give unexpected results. In fact, it is generally accepted that increasing the frequency leads to an accelerated ageing process, mainly due to partial discharge activity, and therefore, to a reduced time to breakdown. The collected results show that increasing the applied voltage frequency, the time to breakdown increases since the electrical treeing shape changes. During this analysis, PD measurement is carried out in order to monitor the electrical treeing evolution during the degradation process by adopting the optimized HFCT-based measurement system.

L’urgence énergétique mondiale impose d’utiliser des systèmes plus économes en énergie. De plus, il devient nécessaire d’effectuer une transition énergétique vers des technologies rejetant moins de gaz à effet de serre. Pour ces raisons, les technologies à base de puissances pulsées auront un rôle à jouer dans le panel énergétique de demain.De nombreuses ressources se situent sous la surface de notre planète (eau, gaz, énergies fossiles, minéraux précieux, énergie géothermique ...). De plus, l’urbanisation de nos villes avec le développement des moyens de transport, du traitement des eaux usées, des réseaux électriques et de chaleurs nous pousse à exploiter l’espace sous terrain. Pour cette exploitation, la mise en place de méthodes industrielles est inévitable pour permettre un avancement rapide, économe en énergie et à moindre coût de production. Les méthodes actuelles de concassage, fracturation ou forage se heurtent néanmoins à une faible vitesse de production lors du traitement de roches dures et abrasives. La fracturation dite électrique pourrait être une méthode alternative. Cette technique utilise des décharges électriques dans des fluides pour concasser les roches.L’objet de cette thèse est d’établir une base de données expérimentales pour la compréhension, la prédiction et l’optimisation du processus. Il s’agit plus particulièrement d’étudier l’influence de l’ensemble des paramètres liés à la fois aux propriétés du milieu (température, conductivité et pression) et aux caractéristiques du circuit électrique sur la rigidité diélectrique des isolants testés. Une attention particulière est portée à la maîtrise de la phénoménologie de la décharge dans ces conditions expérimentales.Dans ce manuscrit, les décharges électriques sont caractérisées à partir d’essais expérimentaux qui sont interprétés par l’intermédiaire d’études théoriques et de simulations numériques. Dans un premier temps, la tension minimale nécessaire pour amorcer un arc est déterminée par la méthode U50 et sa consommation d’énergie associée est calculée. Ces essais sont réalisés à la fois en fonction des paramètres internes au système d’impulsions (énergie stockée, tension d’alimentation et géométrie des électrodes) et aussi en fonction de paramètres externes (conductivité, pression et température du milieu). Dans un second temps, le seuil de champ électrique qui permet de changer de mode de claquage est déterminé en fonction des paramètres externes au système d‘impulsions. Cette transition entre le mode subsonique et le mode supersonique est déterminée à partir du temps de propagation de la décharge électrique et de la consommation d’énergie pendant la phase de pré-arc. Les conditions menant à l’amorçage de l’arc électrique dans les fluides ou dans les roches sont comparées. Une attention particulière est donnée à la résistance de l’arc et au courant maximal qui définissent la puissance transmise au milieu
The global energy emergency requires more energy-efficient systems. In addition, it is necessary to make an energy transition to technologies that emit less greenhouse gases. For these reasons, pulse power technologies will have a role to play in tomorrow’s energy mix.Many resources are located below the surface of our planet (water, gas, fossil fuels, precious minerals, geothermal energy...). In addition, the urbanization of our cities with the development of means of transport, wastewater treatment, electricity and heat networks pushes us to exploit the underground space. For this operation, the implementation of industrial methods is inevitable in allowing a fast, energy-efficient and low-cost production. However, current methods of crushing, fracturing or drilling encounter a low production rate when processing hard and abrasive rocks. The fracturing method called electric fracturing could be an alternative method. This method uses electrical discharges in fluids to crush rocks.The purpose of this thesis is to establish an experimental database for understanding, predicting and optimizing the process. In particular, the influence of all parameters related to both the properties of the medium (temperature, conductivity and pressure) and the characteristics of the electrical circuit on the insulators dielectric strength tested must be studied. Particular attention is paid to controlling the phenomenology of the landfill under these experimental conditions.In this manuscript, electrical discharges are characterized on the basis of experimental tests that are interpreted through theoretical studies and numerical simulations. First, the minimum voltage required to initiate an arc is determined by the U50 method and its associated energy consumption is calculated. These tests are performed both according to the internal parameters of the pulse system (stored energy, supply voltage and electrode geometry) and also according to external parameters (conductivity, pressure and temperature of the medium). In a second step, the electric field threshold that allows to change the breakdown mode is determined according to the parameters external to the pulse system. This transition from subsonic to supersonic mode is determined from the propagation time of the electrical discharge and the energy consumption during the pre-arc phase. The conditions leading to the initiation of the electric arc in fluids or rocks are compared. Particular attention is paid to the arc resistance and maximum current that define the power transmitted in the medium

La filière viti-vinicole se doit de trouver des solutions au cours des années à venir afin de réduire son impact carbone de 20% et de proposer rapidement des alternatives au dioxyde de soufre. Ainsi, ce travail de thèse sur les champs électriques pulsés propose aux professionnels du vin une éco-innovation qui pourrait aider à répondre à ces deux problématiques. L’éco-innovation est de plus en plus considérée comme la clé de la compétitivité future dans le cadre du développement durable. Toutefois, avant d’être intégrée dans la production du vin, l’éco-innovation doit démontrer sa performance et son efficacité sans nuire à la qualité du produit et à la sécurité des consommateurs et doit être approuvée par les instances gouvernementales (OIV, UE...). A ce titre, la thèse a reçu un soutien financier conjoint du CIVB et de l’ADEME. Le principe des Champs Electriques Pulsés (CEP) est d’appliquer à un produit des impulsions électriques de quelques kilovolts durant un temps très court (quelques microsecondes) et répétées n fois. Les cellules contenues dans le produit traité (raisins, moût ou vin) voient leur potentiel transmembranaire augmenter jusqu’à l’induction de pores dans les membranes. L’irréversibilité des pores aboutit à l’extraction des composés cellulaires mais aussi à la mort des cellules. Ainsi, cette technologie, suivant le moment de son application en vinification et les paramètres opératoires, permet l’extraction des composés d’intérêts organoleptiques tels que les polyphénols mais aussi l’inactivation des microorganismes. Les CEP prennent en compte trois aspects importants pour la durabilité d’une technologie: l'environnement, l'économie et la qualité. En effet, cette technique a une série d'avantages pour le producteur de vins: elle est propre, rapide, peu chère, efficace, industrialisable et automatisable. Comparée à d’autres traitements tels que la pasteurisation, la filtration stérilisante, la thermovinification, la macération à chaud ou à froid, la cryoextraction ou encore la flash-détente, la consommation d'énergie est faible (quelques dizaines de kWh/tonne). La technologie des CEP est respectueuse de l’environnement puisqu’elle nécessite peu d’énergie et aucun intrant chimique. Elle est rapide et efficace car la durée du traitement n’est que de quelques dizaines à centaines de millisecondes. Enfin, les CEP sont une technologie non thermique et donc ne dégradent pas les molécules thermosensibles telles que les arômes. Les objectifs de ce travail de recherche ont été de comprendre l’effet des CEP sur les cellules, de déterminer les paramètres de traitement des CEP à employer pour réaliser l’extraction de composés d’intérêt des raisins et pour inactiver des microorganismes afin de stopper la fermentation alcoolique des vins liquoreux et de stabiliser microbiologiquement les vins rouges avant leur mise en bouteille en conservant la qualité du produit traité
The wine industry needs to find solutions in the coming years to reduce its carbon footprint by 20% and quickly propose alternatives to sulphur dioxide usage. This work on pulsed electric fields offers wine professionals an eco-innovation that could help to address these two issues. Eco-innovation is increasingly seen as the key to future competitiveness in the context of sustainable development. However, before being integrated in wine production, eco-innovation must demonstrate its performance and efficiency without compromising product quality and consumers safety so that it could be approved by government authorities (OIV, EU ...). As such, this thesis has received a joint financial support from the CIVB and the ADEME. The principle of Pulsed Electric Field (PEF) is to apply to a product; electrical pulses of a few kilovolts in a very short period time (a few microseconds) and then repeated n times. During treatment (grapes, grape must or wine) cells transmembrane potential increases till the induction of pores in the membranes. The irreversibility of the pores leads not only to the extraction of cellular components but also cell death. Thus, depending on the time of this technology application in winemaking and operating parameters, allows the extraction of sensory interests compounds such as polyphenols or the inactivation of microorganisms. PEF takes into account three important aspects to the sustainability of a technology: environment, economy and quality. This technique has a number of advantages for wine producers: clean, fast, inexpensive, efficient, industrializable and automated. Compared to other treatments such as pasteurization, sterile filtration, thermovinification, hot or cold maceration, cryoextraction or flash-release, its energy consumption is low (a few tens of kWh / tonne). PEF technology is environmentally friendly, as it requires little energy and no chemical inputs. It is fast and efficient because the processing time is only a few tens to hundreds of milliseconds. Finally, this technique is a non-thermal and therefore does not degrade the heat-sensitive molecules such as flavours. The objectives of this research work was to understand the effect of PEF on the cells, to determine the processing parameters during the extraction of compounds of interest grapes and to inactivate microorganisms in order to stop alcoholic fermentation of sweet wines and stabilize microbiologically red wines before bottling maintaining the quality of the processed product

Ce travail porte sur la caractérisation optique et électrique ainsi que la modélisation mathématique du contournement d’isolateurs pollués en tenant compte de la forme de tension appliquée, de la répartition ainsi que de la constitution chimique du dépôt polluant. Sous tension de choc de foudre (1,2/50μs), la morphologie des décharges ainsi que les courants associés dépendent de la tension (forme, amplitude, polarité),de la répartition de la pollution et de sa conductivité. Les vitesses moyennes de la décharge mesurées dépendent de la polarité appliquée à la pointe et de la conductivité de la pollution. Le temps critique correspondant aux conditions critiques est de l’ordre de 9/10 du temps total de contournement quelles que soient la polarité de la tension et la conductivité de la pollution. La constitution chimique de la couche de pollution a peu d’effet sur la tension critique contrairement aux courants critiques. Les valeurs des constantes caractéristiques n et N sont fonction de la nature chimique des dépôts et de la polarité de la tension. Le modèle élaboré montre que les constantes caractéristiques de la décharge n et N sont des paramètres dynamiques et dépendent des éléments du circuit électrique équivalent du système et des paramètres thermiques de la décharge. Les relations des conditions critiques du contournement développé relient les paramètres électriques et thermiques du circuit équivalent et la condition de propagation de la décharge. L’application de ce modèle, pour différentes formes de tension et pour plusieurs types de pollution, donne des résultats satisfaisants. L’hypothèse selon laquelle la colonne de la décharge ne contient que de la vapeur d’eau et de l’air constitue une bonne approximation des grandeurs critiques. Sous tension de choc de foudre, les courants et les tensions critiques dépendent de la configuration de la pollution et de la polarité de la tension. Le courant circule à travers une section effective de la pollution. L’introduction de la notion d’épaisseur critique effective et son application au calcul des grandeurs critiques donne de bons résultats pour les cas de figures étudiés. L’épaisseur effective du dépôt est proportionnelle la résistivité de la pollution et dépend dela configuration de la pollution et de la polarité de la pointe. Dans le cas de dépôt de pollution discontinue et/ou non uniforme, les conditions de propagation des décharges sont locales et leurs paramètres caractéristiques varient selon la configuration et la conductivité du dépôt ainsi que la polarité de la tension appliquée. Le modèle développé pour ce cas de figure donne de bons résultats
This work aimed on optical and electrical characterization and mathematical modeling of flashover of polluted insulators, taking into account the applied voltage waveform, the distribution and chemical composition of pollutant deposit. Under lightning impulse voltage (1.2 /50μs), the morphology of the discharge and the associated currents depend on voltage (shape, amplitude, polarity), the distribution ofpollution and its conductivity. The measured average velocity of the discharge depends on the polarity applied to the tip and the pollution conductivity. The critical time corresponding to the critical conditions is about 9/10 of total flashover duration regardless of the polarity of the voltage and the pollution conductivity. The chemical composition of the pollution layer has little effect on the critical voltage unlike the critical currents. The values of the characteristic constants n and N depend on the chemical nature of the deposits and the voltage polarity.The developed model shows that the discharge constant characteristics n and N are dynamic parameters and depend on the elements of the equivalent electrical circuit system and thermal parameters of the discharge. The developed relationships of critical conditions of flashoverlink the electrical parameters and thermal equivalent circuit and the propagation condition of the discharge. This approach allows us tounderstand the effect of the chemical constitution of pollution on the values of n and N. The application of this model for various voltage waveforms and for several types of pollution, gives satisfactory results. The assumption that the column of the discharge contains only watervapor and air is a good approximation of the critical conditions. Under lightning impulse voltage, the current circulate into a effective section of the pollution surface. The introduction of the concept of critical effective thickness of pollution and its application to the calculation ofcritical parameters gives good results compared with the experimental values. We have also shown that the effective thickness of the depositis proportional to the resistivity of the pollution and depends on voltage polarity and pollution configuration. In the case of discontinuous deposit of pollution and / or non-uniform propagation conditions of discharges are local and their characteristic parameters vary dependingon the configuration and the conductivity of the deposit and the polarity of the applied voltage. The developed model gives good results

Etude de l'aspect statique du contournement, on montre experimentalement que les criteres de wilkins et hampton ne s'appliquent qu'au modele d'obenaus. Mise en evidence de l'importance du champs electrique au voisinage de la decharge. Etude detaillee de la conduction electrolytique et de son evolution pendant le contournement

My diploma thesis is focused on a comparison of direct-current and high frequency (15-80 kHz) electric discharge, which generates non-thermal plasma in water solution of sodium chloride. Mainly current-voltage and Lissajous charts are discussed in the first part of this thesis. These charts describe different discharge phases: electrolysis, bubble formation, discharge breakdown and discharge regular operation in a pin-hole of a dielectric barrier. Influence of frequency, electrolyte conductivity, thickness of the diaphragm (or length of the capillary) and pin-hole diameter on discharge breakdown and bubble generation was studied, too. Measurements were realized in a polycarbonate reactor with total volume of 110 ml, which was divided by a changeable polyacetal insulating wall. This wall divided the reactor into two approximately equal spaces with one stainless steel planar electrode in each part. The Shapal-MTM ceramic discs (thickness of 0.3–1.5 mm and diameter of the central pin-hole of 0.3-0.9 mm) were mounted in the centre of the insulating wall. Initial conductivity of sodium chloride solution was chosen within the interval of 100900 S/cm. The second part of my thesis compares an influence of the direct-current (DC) and high frequency (HF) power sources on physical solution properties (conductivity, pH and temperature) and generation of hydrogen peroxide. A plasma reactor with total volume of 4 l and with mixing set up was divided into two equal spaces with one planar platinum electrode in each part. Diaphragm with thickness of 0.6 mm and pin-hole diameter of 0.6 mm was installed in the middle of the separating wall. Experiment was held at discharge operation of 45 W for 40 minutes with both power sources. Detection of hydrogen peroxide was realised by using a titanium reagent forming a yellow complex, which was analysed by absorption spectroscopy. If HF discharge power is plotted as a function of applied frequency, exponential decrease of frequency with increasing power can be observed. Higher breakdown voltage is necessary for thicker dielectric barriers, on the other hand for bigger diameter of the pin-hole lower breakdown voltage and higher power is needed in DC as well as in HF regime. Breakdown voltage is decreased by the increasing conductivity in both regimes; due to more charge carriers in the higher conductivity lower breakdown voltage is needed. However frequency in HF regime and DC discharge power increases. HF discharge power is decreased by the increasing conductivity. Solution conductivity and temperature are increased by initial conductivity value in both discharge regimes. Solution pH drops to acidic conditions when HF or DC positive regime is applied due to the generation of reactive species and electrolysis (in DC regime). However solution becomes alkaline when DC negative regime is applied. Concentration of hydrogen peroxide is produced linearly when HF or DC negative regime is applied and it depends on initial solution conductivity.

Les decharges partielles ont ete mesurees sur des modeles de condensateurs tout-film dont le dielectrique est du polypropylene (pp) impregne. Ces cellules ont ete alimentees en haute tension alternative. L'influence de l'epaisseur de dielectrique ou des armatures ainsi que les effets de la temperature et du vieillissement ont ete examines. Les representations n() et q#m#o#y() du nombre et de l'amplitude des decharges dans la phase de la tension alternative servent a caracteriser la source de ces decharges : decharges en bord d'armature dans un modele de condensateur sans defaut ou decharges generees par des defauts artificiellement introduits dans la cellule d'etude (defaut d'impregnation, defaut de contact, cavite dans un film de pp, film de pp plie). Le but de cette caracterisation est la constitution d'une base de donnees qui servira a la reconnaissance de la source des decharges sur des appareils industriels et permettra d'estimer la duree de vie de ces appareils. Les tensions d'apparition et d'extinction des decharges partielles (tadp et tedp), l'evolution des decharges en fonction du temps ou de la tension appliquee sont des elements qui servent a la caracterisation des decharges. Cette tache se fait egalement au moyen de parametres calcules a partir des distributions n() et q#m#o#y(). Ces parametres peuvent etre les moments d'ordre 3 et 4 ou bien les parametres que nous avons introduits dans cette etude et qui sont les parametres de position et le parametre d'efficacite energetique. Ces deux derniers parametres sont les plus efficaces car ils permettent a eux seuls de differencier la plupart des cas etudies.

Electrostatic Discharge (ESD) reliability is one of the major reliability concerns in integrated circuits (IC), which if not addressed while designing devices and circuits, can lead to a permanent damage to the Integrated Circuits. The same becomes a rather more stringent in case of system level ESD events (System level ESD), which usually occurs in uncontrolled or harsh environments. To address these issues physical insights into the non-equilibrium electron-phonon (electro-thermal) behaviour of these devices, under nano-second time scale high-current conditions, are required to be developed. These insights are subsequently used to develop reliability aware device. Keeping this larger problem in mind, in this work, we focus on developing physical insights into ESD behaviour of advanced high voltage CMOS/BiCMOS & beyond CMOS device options. Using the physical insights developed, this work also demonstrates using computations and experiment’s reliability aware device design. The thesis/work is divided into following threads: In the first part of this work, insights into various system level ESD problems in advanced High Voltage CMOS devices is developed. High voltage functionalities are the key for building system on chips (SoC) in mobile and automotive products. However, high voltage LDMOS/DeNMOS devices are prone to early ESD induced damages with charge modulation induced current _laments. To withstand extremely high current levels ( 30 A), during system level ESD events, in lowest possible area footprint, Silicon Controlled Rectifier (SCR) solutions are preferred. SCR can switch from a high voltage blocking state to an ohmic state and conduct high current levels. However, implementing SCR in High voltage LDMOS/DeNMOS technologies presents different challenges. First part of the thesis focuses on three of such major challenges i.e. Power scalability, Window failures when stressed through Common Mode Choke (CMC) and Air discharge failures. Furthermore, HBM and CDM qualified HV-SCR devices have found to cause early failures during system level stress conditions. System level discharges can last longer than HBM & CDM time scales (100ns), SCR should survive for pulse widths > 100ns. In this thesis, a unique low current ESD failures in LDMOS based SCRs during snapback is reported for the first time. Failure is universal to LDMOS-SCR devices designed as an efficient MOS switch and found to be specific to a window of current between trigger and holding state and can only be captured using high resistance load-line in Transmission Line Pulse (TLP) test system. This resulted in severe power scalability issues in LDMOS-SCRs for longer stress durations (Pulse width>100 ns). While using systematic experiments and 3D Technology Computer Aided Design (TCAD) simulations, we have developed detailed physical insights into the low current ESD failure phenomenon in LDMOS-SCR devices. Physical insights developed has resulted in design solutions to avoid low current failure and mitigate power scalability issue without interfering with functional operation and MOS performance. Further, the severity of the power scalability problem with increasing LDMOS voltage classes (from 40V Design to 80V LDMOS) is highlighted with a need for novel design strategies. A systematic design approach is presented to evaluate the effect of different design parameters on LDMOS _lament and SCR turn-on near the snapback region. New design guidelines are presented to improve the power scalability without compromising on its ON-state DC (functional) and Safe Operating Area (SOA) characteristics. On the other hand, signalling at certain high voltage I/Os can go below ground levels. Hence, Bidirectional SCR (BDSCR) protection elements are needed to block high voltage under different stress polarities. Power Scalability of High Voltage BDSCR for long duration pulse discharges (PW >100 ns), is also studied in this thesis. Power scalability trends are found to be sensitive to the Transmission Line Pulse (TLP) measurement set-up. Detailed physical insights into the early formation of current filaments along with filament motion in BDSCR is presented in detail using 3D TCAD. Dynamic current filament motion in Bi-directional high voltage SCRs is found. Back and forth current filament motion is found to improve the power scalability trends in BDSCR devices for long stress durations. Finally, impact of silicide blocking in mitigating filament strength has been studied, which in turn improves the ESD robustness and overall power scalability. The device design and physical understanding from investigations in helped to come-up with a new approach to engineer LDMOS drivers for safe snapback. Proposed method considers engineering both static filament & Dynamic/Moving current filaments in LDMOS design. Dynamic filament motion and its relation to NPN turn-on engineering is studied. A unique window failure in LDMOS near snap-back discussed for the first time in LDMOS designs. The presented approach resulted in 10-time improvement in ESD robustness for self-protecting concepts. Finally, different fundamental questions related to origin of filament motion are explored with the help of engineered LDMOS Designs. Another major challenge in development of HVSCR is, its survival against system level ESD stress through Common Mode Choke (CMC). Some of the communication pins (CAN) in automotive ICs need to pass system level IEC test through choke. CMC is an on-chip component present in ESD stress path. A unique failure mechanism for system level ESD stress through a CM choke is investigated. Presence of choke in stress path is found to change current waveform shape that ESD protection devices experience on-chip. Minor variations in the stress current waveform shape for specific IEC stress levels are found to cause an unexpected window failure in Drain Extended NMOS SCRs (DeNMOS-SCR). 3D TCAD simulations are used to understand the device behaviour and failure under the peculiar two-pulse shaped IEC current waveform. A novel DeNMOS-SCR design is demonstrated to increases ESD robustness against the peculiar two pulse stimulus and to avoid system level ESD failures. Air discharge failure in HV-SCRs is another major bottleneck in developing on- chip system level protections. High voltage BDSCR devices are found to be vulnerable to system level air discharge failures. The failure observed is sporadic in nature and found to be function of pulse rise time. Root cause for such SCR failure sensitivity to specific rise times is studied in detail using Multi-Finger 3D TCAD Simulations. A novel design solution is prosed to improve BDSCR robustness against the air discharge failures. Second part of the thesis focuses on understanding ESD device physics of new transistor concepts such as Tunnel FETs and graphene-based FETs. Current as well as the time evolution of the junction breakdown, device turn-ON, voltage snapback, and finally the failure mechanism is studied using both 2-D and 3-D TCAD simulations In Tunnel FETs. The interaction between the band-to-band tunnelling, avalanche multiplication, and thermal carrier generation leading to voltage snapback and failure is presented in detail, along with the electro-thermal instability initiated _lamentation. Impact of various technology and device design parameters on the ESD behavior and robustness of TFETs is discussed. The obtained details will be useful in designing ESD protection concepts in future TFET technologies. Experimental ESD studies on Graphene FETs using matured technology platform are carried out to study the impact of diffusive vs. ballistic carrier transport and top-gate vs. back-gate on failure mechanisms. Insights on current saturation in graphene FET in ESD time scales and a novel step by step failure in dielectric capped transistors is presented. Finally, influence of various top-gate designs on the ESD performance is reported. Safe Operating area boundary definitions in Graphene FETs is also explored. Obtained insights on device failures in these budding technologies, will help in building stronger ESD protection concepts in graphene-based technologies.

The aerodynamic applications of plasma science is a field of growing interest. Investigations using various approaches have been initiated by several research groups that are designed to manipulate the aerodynamic boundary layer and to re-attach the flow to airfoils. EHD (ElectroHydroDynamic) flow control has proven at least as effective as other methods of boundary layer flow control. In the EHD approach, glow discharge plasma actuators are placed on the wings and fuselage of the aircraft, or on the turbine blades in the engine, to influence the boundary layer flow. This thesis is concerned with plasma actuators based on the OAUGDP ® (One Atmosphere Uniform Glow Discharge Plasma). An actuator consists of two conducting electrodes separated by a dielectric plate. When a sufficiently high RF voltage is supplied to the electrodes, the surrounding air ionizes and forms plasma in regions in which the electric field is above approximately 10 kV/cm. The ionized air, in the presence of an electric field gradient, produces a body force on the neutral gas flow.This work is concerned with two EHD effects: paraelectric flow acceleration and peristaltic flow acceleration. In the paraelectric mode, electric field gradients act on the net charge density of plasma, and the plasma drags the neutral gas along with it due to ion-neutral and electron-neutral Lorentzian collisions. In the peristaltic mode, successive actuators are energized with the same voltage, but increasing phase angles. The first part of this thesis describes experiments at the NASA Langley Research Center, Hampton, VA in the 7 x 11 Inch Low Speed Wind Tunnel in which Pitot tube velocity profile measurements and smoke flow visualization tests were conducted.The second part of this thesis describes the development of a low cost power supply to energize OAUGDP ® plasma actuators. The power supply consists of automotive ignition coil transformers, audio amplifiers, and a DC battery. Using this power supply, plasma actuators were energized at voltages up to 8 kV, and at frequencies between 0.5 and 8 kHz. This thesis also presents illustrative paraelectric flow acceleration data obtained using the low-cost power supply.

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.

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.

Transmission of bulk electric power from the generating stations to the load centres can be carried out only through high voltages transmission lines. One of the main issues in the design and maintenance of extra and ultra-high voltage transmission system is the phenomenon named corona. It is the local electrical breakdown of air in the vicinity of the line conductors and hardware. Even though the design and dimensions of these elements are made considering the corona onset, surface abrasions arising either during installation or operation can lead to intolerable corona. Apart from producing some insignificant chemical reactions and noticeable acoustic noise, they can be a significant source of electromagnetic interference. In the early days, this interference was of concern only to radio and television receptions, however, with extensive use of wide frequency bands for modern applications, it has assumed prime importance. The EMI due to the transmission line corona has been extensively studied and reliable empirical formulas have been proposed. The basis for all the earlier studies was the experimentally measured corona currents. This approach fails for new line designs especially with higher and higher voltages being employed due to non-availability of experimental data. A second approach assumed corona current to be injected into the line and subsequent analysis was carried out based on transmission line model. However, there were assumptions made on the mode of corona current injection into the conductor and the frequency range involved were also not adequate for the modern-day applications. Applicability of transmission line model for analysis is also questionable. From a theoretical perspective, the coupling of the field produced by corona to the conductor was hardly investigated and the total field produced by the corona itself was not quantified. In order to address these serious lacunae, the present work was taken up and it can be considered as the first leap towards the correct picturization, as well as, quantification of the problem. The field produced by the electron avalanche involves noticeable retardation effects. In the literature, only the field produced by arbitrarily moving point charge of fixed strength is given by the Heaviside-Feynman equation. On the contrary, the avalanche involves an arbitrarily moving charge of time varying strength at its head with trailing positive charge, which is almost stationary. Starting from the basics, an analytical expression for the electric field due to an arbitrarily moving point charge of time varying strength is derived which forms a fundamental contribution to Electrodynamics. This is extended to deduce an expression for the total electric field due to an avalanche for the very first time. Suitable validation of the expression is provided through numerical simulation of electric field integral equation. Corona discharge is a complex phenomenon having many distinctly different modes which differ in their visual, as well as, electrical characteristics. Innumerable electron avalanches contribute to the measured corona current with their space-charge acting as a moderator. Therefore, in order to model the corona on conductors, an indirect approach based on linear system theory is proposed. An equivalent spatio-temporal dipole distribution was obtained to produce the measured current on the conductor. The general expression derived for the isolated avalanche is extended for this purpose. Using the above, the means of induction, spatial decay rate of corona current in the close range, its propagation mode and field produced by both avalanche/equivalent dipole and that due to induced current in the conductor, have all been investigated and quantified. In summary, the contributions made in this work are more of fundamental in nature and would be of significant interest to the high voltage power transmission line, as well as, to the communication engineers.

Проект виконано на кафедрі біотехнічних систем Тернопільського національного технічного університету імені Івана Пулюя
Кваліфікаційну роботу магістра присвячено питанням удосконалення методів отримання озону в озоногенераторах шляхом зниження амплітуди напруги живлення електродів озоногенератора при збільшенні частоти напруги до 50 кГц. Також обгрунтовано доцільність застосування напруги у вигляді двополярних прямокутних імпульсів.
The master's qualification work is devoted to the improving the methods for increasing the productivity of ozone generators by reducing the amplitude of the voltage ozone generators electrodes with increasing voltage frequency to 50 kHz. Also, the expediency of applying pressure in the form of bipolar rectangular pulses.
ЗМІСТ ВСТУП 9 РОЗДІЛ 1. ОЗОНОТЕРАПІЯ ТА ОСОБЛИВОСТІ ЗАСТОСУВАННЯ ЇЇ В МЕДИЦИНІ 11 1.1 Поняття озонотерапії 11 1.2 Біохімічні та біологічні властивості 15 1.3 Основні методи озонотерапії 19 1.4 Висновки до розділу 1 21 РОЗДІЛ 2. ТЕХНІЧНІ ЗАСОБИ ПРОВЕДЕННЯ ОЗОНОТЕРАПІЇ 22 2.1 Виробництво озону для медичних цілей 22 2.2 Принципи роботи озонаторів 28 2.3 Аналіз стану виробництва озонаторного обладнання 30 2.4 Висновки до розділу 2 49 РОЗДІЛ 3. МЕТОДИ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ОЗОНОГЕНЕРАТОРІВ 50 3.1 Схемо-технічні методи підвищення продуктивності озоногенераторів 50 3.2 Висновки до розділу 3 66 РОЗДІЛ 4. ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ 67 4.1 Методи підвищення ефективності озоногенераторів 67 4.2 Висновки до розділу 4 73 РОЗДІЛ 5. СПЕЦАЛЬНА ЧАСТИНА 74 5.1 Методика проведення медико-біологічних досліджень 74 5.2 Обґрунтування вибору УДК напряму наукового дослідження 80 РОЗДІЛ 6. ОБГРУНТУВАННЯ ЕКОНОМІЧНОЇ ЕФЕКТИВНОСТІ 82 6.1 Науково-технічна актуальність науково-дослідної роботи 82 6.2 Розрахунок витрат на проведення науково-дослідної роботи 83 6.3 Науково-технічна ефективність науково-дослідної роботи 89 6.4 Висновки до розділу 6 93 РОЗДІЛ 7. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 94 7.1 Охорона праці 94 7.2 Безпека в надзвичайних ситуаціях 97 РОЗДІЛ 8. ЕКОЛОГІЯ 103 8.1 Актуальність охорони навколишнього середовища 103 8.2 Основні джерела забруднення довкілля, що виникають у результаті виготовлення озоногенераторів 103 8.3 Заходи щодо зменшення забруднення довкілля 106 ЗАГАЛЬНІ ВИСНОВКИ 108 Бібліографія 110 ДОДАТКИ 112