Engineering Properties of Superconducting Materials

Plastic (and microplastic) pollution has been described as one of the greatest environmental challenges of our time, and a hallmark of the human-driven epoch known as the Anthropocene. It has gained the attention of the general public, governments, and environmental scientists worldwide. To date, the main focus has been on plastics in the marine environment, but interest in the presence and effects of plastics in freshwaters has increased in the recent years. The occurrence of plastics within inland lakes and rivers, as well as their biota, has been demonstrated. Experiments with freshwater organisms have started to explore the direct and indirect effects resulting from plastic exposure. There is a clear need for further research, and a dedicated space for its dissemination. This book is devoted to highlighting current research from around the world on the prevalence, fate, and effects of plastic in freshwater environments

Development of an Air Coil Superconducting Fault Current Limiter

Electrical power grids are the lifeline of technical infrastructure and fundamental for industry and modern lives. Fault Currents can disrupt the continuous supply of electrical energy, cause instable grid conditions and damage electrical equipment. The Air Coil Superconducting Fault Current Limiter (AC-SFCL) is a measure to effectively limit fault currents. The concept is investigated and proven experimentally by designing, building and successfully testing a 60 kV, 400 V, z = 6% demonstrator

Development of an Air Coil Superconducting Fault Current Limiter

Electrical power grids are the lifeline of technical infrastructure and fundamental for industry and modern lives. Fault Currents can disrupt the continuous supply of electrical energy, cause instable grid conditions and damage electrical equipment. The Air Coil Superconducting Fault Current Limiter (AC-SFCL) is a measure to effectively limit fault currents. The concept is investigated and proven experimentally by designing, building and successfully testing a 60 kV, 400 V, z = 6% demonstrator

Impact Of Fault Current Limiters And Demand Response On Electric Utility Asset Management Programs

Over-currents are known to be the dominant cause of power system component failures or deterioration from full functionality. Some of these effects may remain unknown and could later result in catastrophic failures of the entire or large portions of the system. There are plenty of devices/methods available to limit the undesirable consequences of the over-current events. These devices/methods have great impact on system reliability by reducing stress on power system components and increasing their useful lifetime. Due to the importance of the subject, there is tremendous need to analyze and compare these devices/methods in terms of reliability. However, few researches have been reported on analyzing reliability impacts of these devices. Reported studies, in the meantime, appear to have investigated these effects qualitatively rather than quantitatively. This is mainly due to lack of a mathematical model to study the direct impacts of over-current values on system reliability. The main stream of reliability calculations are normally based on statistical measures of system outages rather than electrical parameters such as over-current values. Over-currents usually appear in two common forms of fault currents and overload currents. Fault Current Limiters (FCL) and protection devices are commonly used to limit the impact of fault currents. FCL’s limit the magnitude of fault currents and protection devices limit the exposure time of the component to the fault current and therefore have great impact on increasing the lifetime of the components. Overloads, on the other hand, have smaller magnitudes than those of fault currents but can still be destructive because of normally much longer exposure times. Overcoming overload problems usually requires control strategies such as generation rescheduling, and/or load shedding, and optimized usage of existing assets. Using Demand Response (DR) programs are one of the most effective ways of reducing overload burdens on the power system. In this dissertation, simulation models are developed and used to determine the effect of FCL on reducing the magnitude of fault currents. Various case studies will be performed to calculate the effectiveness of FCL’s in real power system applications. Then, security/dependability studies on the protection systems will be performed to analyze and calculate their effectiveness in reducing exposure times to fault currents. Based on the calculated indices, proper selection of protection schemes can be made based on the desired level of dependability/security. In the next part of the work, a mathematical model is developed to calculate the effect of fault current magnitude and duration on the reliability and asset management. Using the developed model and results of the earlier sections of this research work, the impact of protection systems and FCL devices on reliability and asset management programs are quantitatively calculated and compared. The results from such studies will assist in maintenance planning and in proper selection of the fault current limiting devices with regards to desired reliability and asset management programs. DR programs are introduced and modeled in this dissertation as an effective tool in reducing overload burdens on power system components. Using the developed mathematical model, DR programs are studied and compared in terms of reliability improvement that they provide by preventing unnecessary increase in the component failure rates

Technological solutions and laser processes for the development of superconductor-based applications.

El trabajo realizado en esta tesis doctoral aborda diferentes retos asociados con la implantación de tecnología superconductora en diversas aplicaciones. En la primera parte, se analiza la estabilidad térmica de cables y bobinas superconductoras. En particular, se ha estudiado la generación y propagación de quench en cables de diboruro de magnesio (MgB2) con geometría Rutherford. Se han empleado dos configuraciones para estudiar la dinámica de quench en estos conductores: la generación de calor localizada, simulando un punto caliente gracias a un calentador externo; y la aplicación de sobrecorrientes (corrientes por encima de la corriente crítica del cable). Además, se ha analizado la estabilidad térmica de una bobina tipo doble pancake fabricada con cinta de material superconductor de alta temperatura de segunda generación (2G-HTS), la cual se bobinó de forma continua y sin aislamiento entre espiras. La bobina se ancló térmicamente al dedo frío de un crio-generador para ser enfriada por conducción. Se ha analizado el comportamiento térmico y electromagnético de esta bobina incluyendo los procesos de carga y de descarga, la medida de la corriente crítica de la bobina, las pérdidas generadas, y sus diferentes contribuciones, durante las rampas de carga y descarga, así como la conductancia térmica que se establece en las diferentes uniones térmicas que se han utilizado para refrigerar la bobina.Para poder realizar estos estudios fue necesario inyectar de forma estable corrientes por encima de los 400 A. Esto supuso un reto por el calor generado en el equipo y en las barras de corriente, con un extremo a temperatura ambiente y otro a temperaturas criogénicas, por lo que son necesarios disipadores térmicos, que deben tener buena conductancia térmica y aislamiento eléctrico. En esta tesis se ha propuesto para esta aplicación emplear piezas de cobre recubiertas por una capa de alúmina proyectada por plasma, que es posteriormente densificada y re-fundida mediante el procesado láser de superficies, consiguiendo así una mejora notable de su conductividad térmica.Otro de los objetivos que se han abordado en este trabajo fue estudiar si las propiedades superconductoras pueden verse modificadas por la interacción con radiación láser. La versatilidad de las tecnologías láser permite facilitar la formación de nanoestructuras en la superficie del material con una disposición casi periódica, lo que abre un nuevo camino a la ingeniería de superficies. En esta tesis se ha estudiado como los tratamientos láser pueden modificar las propiedades superconductoras del material. Para estos estudios se han utilizado muestras de niobio por ser el elemento puro superconductor con una temperatura crítica y campos magnéticos críticos más altos. Dichas estructuras han sido generadas con distintos láseres: un láser ultravioleta con pulsos en el rango de cientos de picosegundos, y dos láseres que emiten pulsos en el infrarrojo cercano en el rango de los femtosegundos. Además, se han estudiado tratamientos en diferentes atmósferas. Esta modificación superficial es de gran interés para una aplicación directa del material, como es la construcción de cavidades resonantes de radio frecuencia.<br /

Numerical Electromagnetic Modeling of HTS Power Transmission Cables

RÉSUMÉ Cette thèse de doctorat est divisée en deux parties. L’objectif de la première partie était de développer un modèle numérique rapide et précis pour résoudre le problème électromagnétique de conducteurs en ruban bobinés de façon hélicoïdale. Cette méthode peut être utilisée pour trouver la distribution de courant et les pertes AC dans des applications utilisant des matériaux supraconducteurs à haute température critique (HTS) destinés aux réseaux électriques. Dans la seconde partie du projet, le modèle développé est utilisé pour réaliser des analyses paramétriques du comportement des pertes AC pour un agencement de rubans de HTS disposés sur une même couche, pour différents paramètres de conception. Le principal objectif de ces études était de minimiser les pertes AC en trouvant les paramètres optimaux pour divers agencements de rubans. Dans la production récente de câbles de puissance HTS, les "coated tapes" sont les conducteurs privilégiés. L’épaisseur de la couche supra est d’environ 1 à 2 μm. Selon l’application, sa largeur varie de 4 à 12 mm. Dans la conception de câbles, ces rubans sont bobinés de façon hélicoïdale en simple couche ou couches multiples, sur une forme (support) cylindrique central. La géométrie complexe des rubans ainsi que la non-linéarité de la résistivité de la couche supraconductrice rendent difficiles la résolution de ce problème électromagnétique. Dans la première partie de cette thèse, nous avons introduit une méthode numérique pour calculer la distribution du courant et du champ dans des conducteurs minces bobinés hélicoïdalement, lorsqu’un ou plusieurs de ces conducteurs sont assemblés de façon symétrique. D’après les considérations symétriques associées à la géométrie du problème, et en négligeant l’épaisseur des rubans, le vrai problème 3-D peut être réduit en un problème 1-D dont le domaine se situe sur l’axe central situé à la mi-épaisseur des rubans (suivant la largeur) constituant le câble. La version basse fréquence de l’équation des courant de Foucault est discrétisée dans le domaine réduit d’étude. Pour établir une relation directe entre la densité de courant et le vecteur potentiel dans la formulation du problème, la solution de l’intégrale de Biot-Savart est utilisée pour trouver le vecteur potentiel magnétique dans les couches de courant.----------ABSTRACT This Ph.D. thesis consists of two successive phases. The objective of the first phase was to develop a fast and accurate numerical model to solve the electromagnetic problem of helically wound thin tape conductors. This method must be applicable to find current distribution and AC losses in High Temperature Superconducting (HTS) power transmission cables made of coated tapes. In the second phase of the project, the developed model was used to perform parametric analysis of the AC loss behavior of single layer HTS cables with different design schemes and design parameters. The main objective of this phase was focused on the minimization of AC losses in HTS cables either by searching for optimal designs parameters or alternative design schemes. In the latest generation of HTS power cables, superconducting coated tapes are the conductors of choice. The thickness of the superconducting layer of these tapes is around 1 to 2 μm, and depending on the application, their width varies from 4 to 12 mm. In the cable design, such tapes are helically wound around cylindrical formers in single or multi-layer arrangements. The complicated geometry of the tapes as well as the non-linear resistivity of their superconducting layer, make the accurate solution of the electromagnetic problem of HTS cables quite challenging. During the first phase of this thesis, we introduced a numerical method to compute current and field distribution in helically wound thin tape conductors when one or many of them are arranged in a symmetrical manner. According to the symmetry arguments associated with the geometry of the problem, and neglecting the thickness of the tapes, the real 3-D problem of helically wound tapes could be reduced to a computationally small 1-D problem whose domain lies along the half-width of any of the constituting tapes. The low frequency version of the eddy current equation, as the governing equation of the problem, is discretized over this reduced dimension study domain. To establish a direct relationship between the current density and the vector potential in the problem formulation, the solution of the Biot-Savart integral to find the magnetic vector potential of helically wound current sheets is used

Design of a SFCL with an Inductive Stage in Series with a Resistive Stage Which Transits by Magnetic Field

Part 8: Energy ControlInternational audienceOne of the most interesting applications of superconductors in power systems is the so called “Superconductor Fault Current Limiter (SFCL)”. This is a device that makes the lines exhibit a variable short-circuit impedance: very low (almost null) under normal operation, and high when the current increases above the security limit of the line. There are two types of SFCL: resistive and inductive. The first one consists of a superconducting element in series with the line. The element is designed with a critical current equal the security limit of the line. When the current in the line is higher, the element transits and a high resistance arises, protecting the line. The second type is connected in series with the line too. It consists of an inductor with the magnetic core shielded by a superconducting screen. The screen is designed to transit by magnetic field when the current in the coil (line current) is higher than the security limit of the line. At this time, a high reactance arises protecting the line. The PhD thesis we are working on is a new concept of SFCL with two stages (resistive and inductive) in series designed to solve some problems of each type separately. In this case, the resistive stage is located in the gap of the inductive stage magnetic core. Firstly, the objective is to make the magnetic screen transit. When this happens, the magnetic field penetrates the core and surrounds the resistive stage provoking its transition. In this paper, we present the work philosophy of this novel device, which does not have equivalent in conventional (non-superconducting) technology