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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Standardisering och modularisering av lågspänningsställverken i ABB:s HVDC-stationer. / Standardization and modularization of low-voltageswitchgear in ABB’s HVDC-stations

Nilsson, Daniel, Berg, Sebastian January 2010 (has links)
<p>Den här rapporten undersöker möjligheterna att standardisera och modulariseralågspänningsställverken i ABB:s HVDC-stationer. Anläggningarna har idag heltkundanpassade lösningar, vilket tar för lång tid att projektera för att kunna svara mot denökade efterfrågan på HVDC-lösningar.Arbetet baseras på tretton stationer i åtta pågående och avslutade projekt. Dessa skiljer sigtill storlek, lokalisering, ålder, dokumentation och stationstyp.För att kunna erhålla en korrekt men samtidigt överskådlig bild överlågspäninngsställverkets laster, granskades varje stations dokumentation. Informationensammanställdes i en databas, som visade de belastningar som var ständigt återkommande.Arbetet visar att det är möjligt att standardisera valda delar av lågspänningsställverken, docktas ingen hänsyn till vare sig storleks- eller kostnadsökning. Arbetet behandlar de mestfrekvent förekommande brytarstorlekarna för de typiska lasterna.Det standardförslag som tagits fram har anpassats för att täcka de brytarstorlekar somförekommit för de typiska lasterna i stationerna. För strömriktartransformatorerna erbjudstvå varianter av skåp, medan det för övriga laster endast förekommer ett alternativ.En alternativ lösning på problemet skulle kunna vara att ta fram en standard för varjestationstyp. Detta förutsätter dock ett större antal projekt av varje typ än de som tagits medi detta arbete.</p> / <p>This thesis investigates the possibilities to standardize and modularize the low-voltageswitchgear in ABB’s HVDC-stations. The reason for this is that the customized solutionthey use today take too much engineering and production time to meet the expectedincrease of projects.The report is based on thirteen stations in eight different closed or ongoing projects. Theselection was based on the station size, geographical location, commissioning year andstation type.In order to obtain a correct representation of the loads in the low-voltage switchgear, therelevant station documentation was reviewed and compiled in a database. The data wasthen analyzed to determine the most frequently occurring loads and their characteristics.The thesis shows that it’s possible to standardize some components in the low-voltageswitchgear. However, this report doesn’t take into consideration any possible increase oftotal size and cost. It also shows the most frequent sizes of the circuit breakers for each ofthe common loads.The standard proposition for the common loads was developed to cover all the occurringsizes of the circuit breakers in the stations. For the converter transformers coolingequipment there’s two different cubicles to choose from, while the remaining loads islimited to a single alternative.An alternative solution could be to develop a standard for each occurring station type.However, this would require that the data from a larger number of projects, for all stationtypes, are reviewed and compiled.</p>
32

A Study Of Vacuum Interrupter Performance Based On The Characteristics Of Arc Voltage Developed During Current Interruption

Kulkarni, Sandeep Prakash 03 1900 (has links)
A vacuum interrupter is a switching device used in vacuum circuit breakers, which are widely employed in medium voltage circuits for interrupting the short-circuit fault currents. The vacuum interrupter is the chamber in which the arc extinction and hence the current interruption takes place. On the occurrence of a fault, the breaker mechanism separates the contacts of the vacuum interrupter. As the contacts separate, an arc is established between the contacts. The arc evolves in the contact space and extinguishes at or near the current zero, thus interrupting the current. The processes of arc ignition, evolution and extinction are very complex. These processes are fundamental to the design and the performance of the vacuum interrupter and hence the circuit breaker. The evolution of the arc predominantly depends on the short-circuit current, the design and metallurgy of the contacts. The evolution of the vacuum arc has been the focal point of considerable research activity. Significant effort has been concentrated to understand the various modes of the arc, the transition between the modes, the arc movement and the dependency on the contact design and finally the effect of the arc evolution on the current interruption performance of the vacuum interrupter. The voltage across the contacts during the arcing, termed as the arc voltage, has been a focal point of several research projects. Research has shown that the arc voltage depends strongly on the mode and the evolution process of the arc. The dependency is observed with respect to the magnitude and the nature of the arc voltage. This dependency has been established through the comparison of the arc voltage trace and the actual arc photographs. The arc voltage is thus an important parameter in understanding the arcing process in the interrupter. Arc voltage could also be utilised to compare the arcing behaviour in vacuum interrupters with different contact geometries and metallurgies. Having understood how the arc voltage depends on the arc modes and how it can be used to analyse the arcing performance of the interrupter, this work aims to establish experimentally the dependency of the arc voltage on fundamental parameters of the short-circuit current and the contact design. The variation of the arc voltage is studied with respect to the magnitude of the short-circuit current. It is seen that the magnitude of the arc voltage is higher, for a higher short-circuit current. This dependency is also reflected in the nature of the arc voltage waveform. The effect of cumulative short- circuit operations has been understood through the study of arc voltage variation with respect to the accumulated arcing time. It has been found that the arc voltage consistently decreases as the accumulated arcing time increases. The effect of the contact diameter on the arc evolution has been studied by comparing the arc voltage variations for contacts of different diameters for the same short-circuit current. It is observed that the variation of arc voltage with respect to the contact diameter depends on the type of contact. In the case of radial magnetic field contacts, it has been observed that the arc voltage is lower for a contact with lower diameter. Whereas in the case of axial magnetic field contacts there is an inverse relation between the contact diameter and the arc voltage. Finally, the effect of the type and distribution of the magnetic field on the arc voltage variation as well as the contact erosion has been studied. In general, the observations show that the arc voltage magnitude for the radial magnetic field geometry is higher than the axial magnetic field geometry. Also, there is a significant difference in the appearance of the arc voltage waveforms for the arcs under the two types of magnetic fields. Finite element simulations and short-circuit evaluations have shown that the axial magnetic field contact system with 90 deg coil orientations yield a more uniform distribution of the flux density and hence lower erosion of the contacts. These results show a clear dependence of the arc voltage on the various above mentioned parameters. Thus the arc voltage could be utilised as a diagnostic parameter during the evaluation of the vacuum interrupter. In the present scenario, significant research is being done to increase the breaking capacity of the interrupters. This calls for optimization of design of the existing contacts and the design of novel contact geometries. The arc voltage would be used as an important diagnostic tool in this process. Also, the utilization of vacuum interrupter in high voltage and extra high voltage circuits is being explored. This application requires increase in the contact gap or series connection of gaps. The arc behaviour in longer gaps and gaps connected in series would be an important research area. Again the arc voltage could be used to study the arc evolution in these specialised conditions. The experiments in this research work have been performed on commercial vacuum interrupters. For a dedicated research on vacuum arcs and vacuum interrupter contacts, development of a vacuum arc research facility has also been attempted as a part of this research work.
33

The dynamic behaviour of distance protection relays on series compensated lines under fault conditions.

Magagula, Xolani. January 2014 (has links)
M. Tech. Electrical Engineering / Investigates the reasons behind the poor performance of distance relays on series compensated lines. In order to achieve this objective, a case study will be established in a power system software (DigSilent Power Factory). Furthermore, a practical incident that occurred on Eskom's compensated network will be examined. However, prior to investigating the performance of the distance relay on transmission lines, there are some other critical aspects that have to be thoroughly understood. These aspects include amongst others: transmission line modelling ; numeric relay algorithms ; distance protection philosophies ; series compensation phenomena ; analysis of distance relays performance on both compensated and uncompensated lines and the action and influence of the MOV. The study will provide a better understanding regarding the dynamic behaviour of the impedance protection relay under fault conditions on series compensated lines and the behaviour of the MOV during a fault.
34

Life assessment and life extension of high voltage equipment in transmission substations.

Singh, Omchand. January 2004 (has links)
In order to sustain transmission grid availability and reliability it is imperative that the condition of vital and costly high voltage equipment is ascertained on a continuous or regular basis. It is necessary to establish the effective diagnostic tools or surveillance devices that can be used to assess equipment condition. Emphasis has been placed on refining well-established and more novel but developing condition assessment techniques. It is important to note that condition assessment of equipment also allows the opportunity to predict failure. Based on a complete and systematic assessment, the failure of defective equipment may be evident or predicted in time, thus preventing a forced outage and loss of valuable 'system minutes'. It has also become necessary to extend the life of existing equipment since most of them are reaching the end of their useful life. Replacement strategies have proven to be ineffective due to financial and resource constraints experienced by utilities. Life extension is the work required to keep equipment operating economically beyond its anticipated life, with optimum availability, efficiency and safety. One of its principal components is condition assessment, with the possibility of predicting remnant life. As a result, refurbishment projects are then raised. Refurbishment by replacement, uprating, modifications or change of design of certain key components to extend the life usually requires a substantial amount of capital to be invested. These projects must be economically justified. This thesis focuses on establishing condition assessment techniques for major power equipment such as power transformers. Assessment techniques for instrument transformers and circuit breakers are included, since these are commonly replaced or modified under refurbishment projects. An experimental investigation was carried out to determine the effectiveness of integrating data of two diagnostic techniques i.e. dissolved gas analysis (on-line) and acoustic detection of partial discharges. It was found that there is a correlation between data obtained from an acoustic detection system and an on-line single gas (Hydrogen) analyser. By integrating the data of both on-line monitoring systems, the diagnostic process is further enhanced. In addition, the location of a fixed discharge source was verified by using an acoustic detection system. Further, the sensitivity of the acoustic technique to partial discharge inception voltage, relative to the established electrical detection technique was determined for the experimental arrangement used. The results obtained indicated that this is an effective technique for the evaluation of activity within a transformer structure. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2004.
35

Condition measuring and lifetime modelling of electrical power transmission equipment

Westerlund, Per January 2015 (has links)
The electric grid is important in modern society, so the outages should be few. The transmission grid should have a real high availability, since it transports electrical energy across the country. Then, it is difficult to plan outages for maintenance and installation. This thesis lists twenty surveys about failures of circuit breakers and disconnectors, with data about the cause and the lifetime. It also contains a survey of about forty condition-measuring methods for circuit breakers and disconnectors, mostly applicable to the electric contacts and the mechanical parts. As there is no published method to monitor the electric contacts at voltages around 400 kV, a system with IR sensors has been installed at the nine contacts of six disconnectors. The purpose is to avoid outages for maintenance by estimating the condition of the contacts while the disconnectors are still connected to high voltage. The measured temperatures are collected by radio and regressed against the square of the current, since the best exponent for the current was found to be 2.0. The coefficient of determination $R^2$ is high, greater than 0.9. This gives for each contact a regression coefficient, which can serve as an estimate of the condition of the contact. The higher the coefficient is, the more heat is produced at the contact, which can damage the material. This enables a ranking of the different contacts and shows which the worst ones are. This coefficient can also give a dynamic rating of the disconnector. / Elnätet är viktigt i det moderna samhället, så antalet avbrott bör vara lågt. Särskilt stamnätet bör ha en särskilt hög tillgänglighet, då det transporterar elektrisk energi tvärsöver landet. Då blir det svårt att planera avbrott för underhåll och utbyggnad. Denna avhandling tar upp tjugo studier av fel i brytare och frånskiljare med data om felorsak och livslängd. Den har också en översikt av ett fyrtiotal olika metoder för tillståndsmätningar för brytare och frånskiljare, som huvudsakligen rör de elektriska kontakterna och de mekaniska delarna. Eftersom det inte finns någon beskriven metod för att övervaka elektriska kontakter för spänningar på runt 400 kV, har ett system med IR sensorer installerats på de nio kontakterna på sex frånskiljare. Målet är att minska antalet avbrott för underhåll genom att skatta skicket hos kontakterna, när frånskiljarna fortfarande är kopplade till högspänning. De uppmätta temperaturerna tas emot genom radio och behandlas genom regression mot kvadraten av strömmen, då den bästa exponenten för strömmen visade sig vara 2,0. Förklaringsfaktorn $R^2$ är hög, över 0,9. För varje kontakt ger det en regressionskoefficient, som blir en skattning av kontaktens skick. Ju högre koefficienten är, desto mer värme utvecklas det i kontakten, vilket kan leda till skador på materialet. Kontakternas olika koefficienter ger en rankordning dem och därmed en möjlighet att prioritera vilken frånskiljare som ska underhållas först. Systemet kan också användas för att minska eller öka den tillåtna strömmen baserat på skicket. / <p>QC 20150522</p>
36

Testing Resilience of Envoy Service Proxy with Microservices

Dattatreya Nadig, Nikhil January 2019 (has links)
Large scale internet services are increasingly implemented as distributed systems to achieve availability, fault tolerance and scalability. To achieve fault tolerance, microservices need to employ different resilience mechanisms such as automatic retries, rate limiting, circuit breaking amongst others to make the services handle failures gracefully and cause minimum damage to the performance of the overall system. These features are provided by service proxies such as Envoy which is deployed as a sidecar (sidecar proxy is an application design pattern which abstracts certain features, such as inter-service communications, monitoring and security, away from the main architecture to ease the tracking and maintenance of the application as a whole), the service proxies are very new developments and are constantly evolving. Evaluating their presence in a system to see if they add latency to the system and understand the advantages provided is crucial in determining their fit in a large scale system.Using an experimental approach, the services are load tested with and without the sidecar proxies in different configurations to determine if the usage of Envoy added latency and if its advantages overshadow its disadvantages. The Envoy sidecar proxy adds latency to the system; however, the benefits it brings in terms of resilience, make the services perform better when there is a high number of failures in the system. / Storskaliga internettjänster implementeras alltmer som distribuerade system för att uppnå tillgänglighet, feltolerans och skalbarhet. För att uppnå feltolerans måste microservices använda olika typer av resiliens mekanismer som automatisk återförsök, hastighetsbegränsning, kretsbrytning bland annat som tillåter tjänsterna att hantera misslyckanden graciöst och orsaka minimala skador på prestandan hos det övergripande systemet. Dessa funktioner tillhandahålls av service proxies som Envoy. Dessa proxies används som sidovagn (sidvagnproxy är ett applikationsdesignmönster som abstraherar vissa funktioner, såsom kommunikation mellan kommunikationstjänster, övervakning och säkerhet, bort från huvudarkitekturen för att underlätta spårningen och underhåll av ansökan som helhet). Dessa tjänster är väldigt nya och utvecklas ständigt. Att utvärdera deras närvaro i ett system för att se om de lägger till latens för systemet och förstå fördelarna som tillhandahålls är avgörande för att bestämma hur väl de skulle passa i ett storskaligt system. Med hjälp av ett experimentellt tillvägagångssätt testas tjänsterna med och utan sidospårproxys i olika konfigurationer för att avgöra om användningen av Envoy lägger till latens och om dess fördelar överskuggar dess nackdelar. Envoy sidecar proxy ökar latensen i systemet; De fördelar som det ger med avseende på resiliens gör tjänsterna bättre när det finns ett stort antal misslyckanden i systemet.
37

On the polymer-based nanocomposites for electrical switching applications

Doddapaneni, Venkatesh January 2017 (has links)
Recent research demonstrated that polymer based nanocomposites (PNCs) have been engineered in order to improve the arc interruption capability of the circuit breakers. PNCs are the combination of nano-sized inorganic nanoparticles (NPs) and polymers, opened up new developments in materials science and engineering applications. Inorganic NPs are selected based on their physical and chemical properties which could make multifunctional PNCs in order to interrupt the electrical arcs effectively. In particular, we presented the PNCs fabricated by using CuO, Fe3O4, ZnO and Au NPs in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method, recently developed method to avoid NPs agglomeration, leading to good spatial distribution in the polymer matrix. Thus, several samples with various wt% of NPs in PMMA matrix have been fabricated. These PNCs have been characterized in detail for the morphology of NPs, interaction between NPs and polymer matrix, and radiative/thermal energy absorption properties. In the next stage, PNCs are tested to determine their arc interruption performance and impact on the electrical arcs of current 1.6 kA generated using a specially designed test set-up. When PNCs interact with the electrical arcs, they generate ablation of chemical species towards core of the electrical arc, resulting in cooling-down the arc due to strong temperature and pressure gradient in the arc quenching domain. This thesis demonstrates for the first time that these engineered PNCs are easily processed, reproducible, and can be used to improve the arc interruption process in electrical switching applications. / Ny forskning har visat att polymerbaserade nanokompositer (PNCs) har utformats för att förbättra strömbrytares förmåga att undvika ljusbågar vid överslag. PNCs är en kombination av nanostora oorganiska nanopartiklar (NP) och polymerer, som har öppnat upp för ny utveckling inom materialvetenskap och tekniska tillämpningar. Oorganiska NP väljs baserat på deras fysikaliska och kemiska egenskaper som kan hjälpa PNCs att motverka elektriska ljusbågar effektivt. I synnerhet, presenterade vi PNCs tillverkade genom användning av CuO, Fe3O4, ZnO och Au NP i en poly (metylmetakrylat) (PMMA)-matris via in situ-polymerisationsmetod, nyligen utvecklad för att undvika NP-agglomerering, vilket leder till god rumslig fördelning i polymermatrisen. Därför har flera prover med olika vikt% av NP i PMMA-matris tillverkats. Dessa PNCs har utvärderats i detalj för NP-morfologi, interaktion mellan NP och polymermatris, och strålnings- och värmeenergiabsorption. I nästa skede testas PNCs för att bestämma deras förmåga att undvika ljusbågar och påverkan på de elektriska ljusbågarna av 1,6 kA strömstyrka, genererade med hjälp av en specialdesignad test-set-up. När PNCs interagerar med de elektriska ljusbågarna, genererar de ablation av kemiska ämnen mot kärnan i den elektriska ljusbågen, vilket resulterar i nedkylning av ljusbågen på grund av starka temperatur- och tryckgradienter i området. Denna avhandling visar för första gången att dessa konstruerade PNCs är lätta att framställa, reproducerbara, och kan användas för att förbättra avbrottsprocessen för ljusbågen i elektriska kopplingstillämpningar. / <p>QC 20170303</p>
38

On the Design of Ultra-fast Electro-Mechanical Actuators

Bissal, Ara January 2013 (has links)
The continuously increasing demand for connecting electric grids with remote renewable energy sources such as wind power and photovoltaic cells has rekindled interest in high voltage direct current (HVDC) multi-terminal networks. Although HVDC networks have numerous benefits, their adoption relies entirely on the availability of HVDC circuit breakers which, compared to traditional alternating current circuit breakers, have to operate in a time frame of milliseconds. This thesis deals with the design of ultra-fast electro-mechanical actuators based on the so-called Thomson coil (TC) actuator. The simulation of a (TC) actuator constitutes a multi-physical problem where electromagnetic, thermal, and mechanical aspects must be considered. Moreover, it is complex since all those variables are co-dependent and have to be solved for simultaneously. As a result, a multi-physics simulation model that can predict the behavior and performance of such actuators with a high degree of accuracy was developed. Furthermore, other actuator concepts were also investigated and modeled in light of searching for a drive with a superior efficiency. The theory behind the force generation principles of two different types of ultra-fast electromechanical actuators, the TC and the double sided coil (DSC), were compared by the use of static, frequency, and comprehensive transient multi-physics finite element simulation models. Although, simulation models serve as a powerful tool for modeling and designing such state of the art actuators, without validation, they are weak and prone to errors since they rely on approximations and simplifications that might not always hold. Therefore, a prototype was built in the laboratory and the model was validated experimentally. Finally, it is important to note that the drives in this thesis are intended to actuate metallic contacts. As such, their behavior and performance upon mechanical loading was studied. Furthermore, some scaling techniques were applied to boost their performance and efficiency. / <p>QC 20130422</p>
39

Modeling and Verification of Ultra-Fast Electro-Mechanical Actuators for HVDC Breakers

Bissal, Ara January 2015 (has links)
The continuously increasing demand for clean renewable energy has rekindled interest in multi-terminal high voltage direct current (HVDC) grids. Although such grids have several advantages and a great potential, their materialization has been thwarted due to the absence of HVDC breakers. In comparison with traditional alternating current (AC) breakers, they should operate and interrupt fault currents in a time frame of a few milliseconds. The aim of this thesis is focused on the design of ultra-fast electro-mechanical actuator systems suitable for such HVDC breakers.Initially, holistic multi-physics and hybrid models with different levels of complexity and computation time were developed to simulate the entire switch. These models were validated by laboratory experiments. Following a generalized analysis, in depth investigations involving simulations complemented with experiments were carried out on two of the sub-components of the switch: the ultra-fast actuator and the damper. The actuator efficiency, final speed, peak current, and maximum force were explored for different design data.The results show that models with different levels of complexity should be used to model the entire switch based on the magnitude of the impulsive forces. Deformations in the form of bending or elongation may deteriorate the efficiency of the actuator losing as much as 35%. If that cannot be avoided, then the developed first order hybrid model should be used since it can simulate the behavior of the mechanical switch with a very good accuracy. Otherwise, a model comprising of an electric circuit coupled to an electromagnetic FEM model with a simple mechanics model, is sufficient.It has been shown that using a housing made of magnetic material such as Permedyn, can boost the efficiency of an actuator by as much as 80%. In light of further optimizing the ultra-fast actuator, a robust optimization algorithm was developed and parallelized. In total, 20520 FEM models were computed successfully for a total simulation time of 7 weeks. One output from this optimization was that a capacitance of 2 mF, a charging voltage of 1100 V and 40 turns yields the highest efficiency (15%) if the desired velocity is between 10 m/s and 12 m/s.The performed studies on the passive magnetic damper showed that the Halbach arrangement gives a damping force that is two and a half times larger than oppositely oriented axially magnetized magnets. Furthermore, the 2D optimization model showed that a copper thickness of 1.5 mm and an iron tube that is 2 mm thick is the optimum damper configuration. / <p>QC 20150422</p>
40

Influence of copper contamination on thermophysical, radiation, and dielectric breakdown properties of CO2-N2 mixtures as replacement of SF6 in circuit breakers / Influence des vapeurs de cuivre sur les propriétés thermo-physiques, radiatives, et diélectriques des mélanges CO2-N2 destinés à remplacer le SF6 dans les disjoncteurs haute-tension

Zhong, Linlin 16 June 2017 (has links)
La thèse porte sur les propriétés thermodynamiques, de transport, de diffusion de rayonnement, et diélectriques des mélanges CO2-N2 contaminés par du cuivre, pour des températures de 300 - 30,000 K et des pressions 0.1 - 16 bar. Les motivations de ce travail ainsi qu'un état de l'art sur le remplacement du SF6 et l'influence des vapeurs métalliques dans de tels dispositifs sont présentés dans le chapitre 1. Le chapitre 2 étudie les compositions à l'équilibre calculées à partir de la méthode de minimisation de l'énergie libre de Gibbs, en considérant la présence de phases condensées dans le plasma. A partir de ces compositions, nous présentons les propriétés thermodynamiques comme la densité de masse, l'enthalpie et la chaleur spécifiques à pressions constante. Les corrections de Virial et Debye-Hückel sont prises en compte pour tenir compte de l'effet des ions et des hautes pressions. Dans le chapitre 3, les coefficients de transport (conductivité électrique, viscosité, et conductivité thermique) et les coefficients de diffusion combinés (coefficients de diffusion ordinaires combinés, ceux liés au champ électrique, aux gradients de pression et de température) sont calculés selon la théorie de Chapman-Enskog. Les intégrales de collision nécessaires au calcul de ces coefficients sont obtenues pour les interactions neutre-neutre et neutre-ion à partir d'un potentiel de Lennard-Jones modifié. Dans le chapitre 4, les coefficients d'émission nette (CEN) sont calculés en considérant le rayonnement des raies atomiques, du continuum atomique, des raies moléculaires et du continuum moléculaire. Les élargissements en pression des raies (élargissements de Van der Waals et de résonance), les élargissements Stark, et l'élargissement sont pris en compte dans la détermination d'un facteur de fuite qui permet de simplifier le calcul du coefficient d'émission des raies. Le rayonnement du continuum atomique tient compte de l'attachement radiatif, de la recombinaison radiative et du Bremsstrahlung. Dans le chapitre 5, les propriétés diélectriques de claquage (incluant la fonction de distribution d'énergie des EEDF), le coefficient réduit d'ionisation réduit, le coefficient réduit d'attachement électronique, le coefficient effectif réduit d'ionisation, et le champ critique réduit) du gaz chaud ont été calculés sur la base de l'approximation à deux termes de l'équation de Boltzmann. Les interactions, incluant les collisions élastiques, excitation, ionisation et attachement entre électrons et espèces neutres sont pris en compte dans la résolution de l'équation de Boltzmann. Les sections efficaces d'ionisation de Cu2 et CuO non disponibles dans la littérature ont été calcules selon la méthode DM. La conclusion des travaux et leurs perspectives sont présentés dans le chapitre. / Sulfur hexafluoride (SF6) is a greenhouse gas designated by the Kyoto Protocol because of its extremely high global warming potential (GWP). CO2, N2, and their mixtures have the potential to replace SF6 in certain applications, such as circuit breakers. In these electric apparatus, copper vapour resulting from the heating of electrodes can modify the characteristics of arc plasmas, which must be taken into account when setting up physical models. This dissertation, therefore, investigates the thermodynamic, transport, diffusion, radiation, and dielectric breakdown properties of CO2-N2 mixtures contaminated by copper at temperatures of 300 - 30,000 K and pressures of 0.1 - 16 bar. The equilibrium compositions are calculated using the minimization of Gibbs free energy with consideration of condensed species. Copper vapour is found to condense at temperatures below 3000 K. Based on the compositions, the thermodynamic properties, including mass density, specific enthalpy, and specific heat at constant enthalpy, are determined according to their definitions. The Debye-Hückel corrections are also considered in the calculation of compositions and thermodynamic properties. The transport coefficients (including electrical conductivity, viscosity, thermal conductivity) and combined diffusion coefficients (including the combined ordinary diffusion coefficient, combined electric field diffusion coefficient, combined temperature diffusion coefficient and combined pressure diffusion coefficient) are calculated based on the Chapman-Enskog theory. The newly developed Lennard-Jones like phenomenological model potential is adopted to describe the neutral-neutral and neutral-ion interactions in determining collision integrals. The net emission coefficients (NEC) of gas mixtures are calculated with considering atomic lines and continuum and molecular bands and continuum. The pressure broadening (Van der Waals broadening and the resonance broadening), Stark broadening, and Doppler broadening are taken into account in the determination of escape factors. The continuum radiation of atoms is described by radiative attachment, radiative recombination, and Bremsstrahlung. The dielectric breakdown properties (including EEDF, reduced ionization coefficient, reduced electron attachment coefficient, reduced effective ionization coefficient, and reduced critical electric field strength) of hot gas mixtures are calculated based on the two-term approximation of the Boltzmann equation. The interactions, including elastic, excitation, ionization and attachment collisions, between electrons and neutral species are taken into account in solving the Boltzmann equation. The ionization cross sections of Cu2 and CuO which are unavailable in literatures are calculated using the DM method. Compared with SF6-Cu mixtures, CO2-N2-Cu mixtures present much different thermophysical, radiation, and dielectric breakdown properties. As an arc quenching gas, CO2-N2-Cu mixtures have lower ??Cp and thermal conductivity at low temperatures but present higher ??Cp, thermal conductivity, and NEC in the medium temperature range. As an insulating medium, the hot CO2-N2-Cu mixtures have much poorer dielectric strength below 2000 K, whereas above 2000 K, they present better dielectric breakdown performance than SF6-Cu mixtures.

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