Contribution for the Study of the Integration of Inductive Superconducting Fault Current Limiters in Electrical Distribution Grids

A wider adoption of distributed generation sources and an increased interconnection of networks tend to increase the complexity of electric power grids, thus causing a surge in failures, especially short-circuits. The conventional solution against short-circuit currents, for example, the construction of new substations, splitting of busbars, even updating the technology of the existing current limiters may prove either economically or technically unfeasible. Fault current limiters, mainly the superconducting fault current limiters, have already demonstrated their viability in electric power grids. Fault current limiter devices at normal operation are invisible to the grid, acting almost instantly upon a fault, returning to their normal state upon its correction. To disseminate these technologies, the development of straightforward design tools is required. These tools must consider the properties of the available constitutive elements of the devices. Behind these design tools, the integrity of the fault current limiter should be assured during its operation. Problems regarding the electrodynamic forces developed under short-circuit events must be properly characterized because they can damage windings, causing device breakage and affecting the power grid. In this thesis, a design methodology that intends to model and optimise saturated cores superconducting fault current limiters is presented. This methodology considers the characteristics of each constitutive element of the limiter while addressing utility requirements and power grid characteristics. Genetic algorithms are used both to optimise the constitutive elements of the limiter and its performance in the power grid. In order to validate the present methodology, a three-phase superconducting fault current limiter is designed/optimised, built and tested. The electrodynamic forces analysis developed in superconducting tapes of an inductive transformer type superconducting fault current limiter, under short-circuit conditions is performed.A crescente adoção de fontes de geração distribuída e o aumento das ligações internas entre redes de energia levou ao aumento da complexidade das redes elétricas, causando um provável aumento do número de falhas, especialmente os curto-circuitos. Soluções convencionais para lidar com curto-circuitos, como por exemplo, a construção de novas subestações, a divisão dos barramentos, ou a atualização tecnológica dos limitadores de corrente existentes, podem se mostrar muito dispendiosas ou tecnicamente inviável. Os limitadores de corrente de defeito, principalmente os dispositivos supercondutores, têm vindo a demostrar a sua viabilidade em redes de energia elétrica. Estes dispositivos são considerados invisíveis para a rede, quando em operação normal. Quando uma falha na rede ocorre, estes agem instantaneamente, retornando ao seu estado normal após a falha terminar. De modo a disseminar estas tecnologias, é necessário o desenvolvimento de ferramentas de projeto e modelação, de fácil uso. Essas ferramentas devem considerar as propriedades dos elementos que constituem os dispositivos de proteção. Por detrás dessas ferramentas de projeto, a integridade do limitador deve ser assegurada durante todo o seu funcionamento. Problemas relacionados com forças eletrodinâmicas desenvolvidas sob eventos de curto-circuito devem ser devidamente caracterizados, pois podem danificar os enrolamentos, e por sua vez o equipamento e afetar a rede elétrica. Nesta tese, é apresentada uma metodologia de projeto, que visa modelar e otimizar limitadores de corrente de defeito supercondutores, do tipo núcleos saturados. Esta metodologia considera as características de cada elemento constitutivo do limitador enquanto aborda os requisitos da concessionária da rede de distribuição de energia e as características da rede elétrica. Algoritmos genéticos são usados para otimizar os o limitador e o seu desempenho na rede elétrica. A fim de validar a metodologia atual, um limitador trifásico é projetado/otimizado, construído e ensaiado. É ainda realizada a análise das forças eletrodinâmicas desenvolvidas em fitas supercondutoras de um limitador de corrente de defeito, do tipo transformador, em condições de curto-circuito

Investigations on corrosion monitor reliability, calibration, and coverage

Thickness loss due to internal corrosion and erosion is a critical issue in ferromagnetic steel structures that can cause catastrophic failures. Ultrasonic thickness gauges are widely used for the detection of wall thickness. Recently permanently installed ultrasonic sensors have become popular for the inspection of areas suspected to undergo wall thickness loss. However, these are limited by the high cost and requirement of coupling agents. To address these problems, a novel cost-effective, and smart corrosion monitor based on the magnetic eddy current technique is developed in this research. The performance and reliability of the monitor to track internal wall thickness loss is tested successfully through accelerated and real-life aging corrosion tests. Due to the handling and safety issues associated with the powerful magnets in magnetic techniques, a particle swarm-based optimisation method is proposed and validated through two test cases. The results indicate that the area of the magnetic excitation circuit could be reduced by 38% without compromising the sensitivity. The reliability of the corrosion monitor is improved by utilising the active redundancy approach to identify and isolate faults in sensors. A real-life aging test is conducted for eight months in an ambient environment through an accelerated corrosion setup. The results obtained from the two corrosion monitors confirm that the proposed corrosion monitor is reliable for tracking the thickness loss. The corrosion monitor is found to be stable against environmental variations. A new in-situ calibration method based on zero-crossing frequency feature is introduced to evaluate the in-situ relative permeability. The thickness of the test specimen could be estimated with an accuracy of ± 0.6 mm. The series of studies conducted in the project reveal that the magnetic corrosion monitor has the capability to detect and quantify uniform wall thickness loss reliably

Advanced Geoscience Remote Sensing

Nowadays, advanced remote sensing technology plays tremendous roles to build a quantitative and comprehensive understanding of how the Earth system operates. The advanced remote sensing technology is also used widely to monitor and survey the natural disasters and man-made pollution. Besides, telecommunication is considered as precise advanced remote sensing technology tool. Indeed precise usages of remote sensing and telecommunication without a comprehensive understanding of mathematics and physics. This book has three parts (i) microwave remote sensing applications, (ii) nuclear, geophysics and telecommunication; and (iii) environment remote sensing investigations

UFGM - 2006 Annual Report

INGV, SEZIONE DI CATANIAPublished2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveope

Structural and physical properties of Fe-Nb-B-RE type of bulk magnetic nanocrystalline alloys

The subject of hard magnetic materials is important from the both practical as well as scientific point of view. Researches in this field are focused on new materials with strong enough hard magnetic properties but with lower rare earth content than for the classical Nd rich alloys. The presented PhD thesis refers to preparation, structural and magnetic properties of the Fe-Nb-B-RE type of bulk nanocrystalline alloys. As the preparation technology of the bulk alloys, the so-called vacuum suction casting was chosen. The chemical compositions of the examined alloys is originated from the Fe-Nb-B (NANOPERM) amorphous melt spun ribbons in which niobium, as an alloying addition, slows down crystallization of iron leading to some optimization of magnetic properties. The PhD thesis is focused on: i) magnetic interactions in multi-phase magnetic materials, ii) magnetism in TM-RE disordered structure, iii) influence of microstructure on selected physical properties and iv) numerical modeling and characterization of the nanomagnetic structures. From application point of view, especially important is a combination of chemical compositions and technology parameters (cooling rate, melting current) of the studied alloys, in order to improve hard magnetic characteristics and / or decrease the RE content without deterioration of their desired properties. The performed investigations consist of fabrication of about 80 different alloys characterized by several structural and magnetic measurement techniques like X-ray diffraction, Mössbauer spectroscopy, DSC, SEM, AFM / MFM, Kerr microscopy, magnetic balance as well as SQUID magnetometer. It was shown that the phase structure, microstructure and magnetic properties strongly depends on the chemical composition (the RE and Nb content) as well as technology parameters (the sample diameter and the melting current). The optimal parameters were established as: i) Tb as the RE element with the content of 10-12 at. %, ii) Nb content of 6-8 at. %, iii) sample diameter ranged from 0.5 to 1.5 mm and iv) melting current I = 35 A. The alloys reveal hard magnetic properties with a high and ultra-high coercivity depending on the niobium content. Particularly, for the field-annealed (Fe80Nb6B14)0.88Tb0.12 alloy, the coercive field measured at room temperature exceeds 7 T which is a unique feature in the case of bulks. The observed magnetic hardening effect is controlled by the niobium content in the combination with the specific solidification rate (during casting). The observed phase segregation leads to the formation of grain microstructure with the irregularly shaped dendrites separated by inter-dendritic regions. This structure is responsible for an additional shape as well as surface anisotropy and thereby it is a source of some ultra-hard magnetic objects. The carried out simulations proved the proposed micro-magnetic picture of the alloys and indicate a significant role of the ultra-hard magnetic objects in the magnetization processes. Generally, as was shown in the presented thesis, the examined alloys can be considered as high and ultra-high coercive materials with application potential in the fields of permanent magnets where increasing resistance to external magnetic field is required