Development and test of resistive superconducting fault current limiter; acting time and its recovery conditions

Resistive-type of superconducting fault current limiters (RSFCL) have been developed for medium voltage class aiming to operate at 1 MVA power capacity and short time recovery (< 2 s). A RSFCL in form of superconducting modular device was designed and constructed using 50 m-length of YBCO coated conductor tapes for operation under 1 kV / 1 kA and acting time of 0.1 s. In order to increase the acting time the RSFCL was combined with an air-core reactor in parallel to increase the fault limiting time up to 1 s. The tests determined the electrical and thermal characteristics of the combined resistive/ inductive protection unit. The combined fault current limiter reached a limiting current of 583 A, corresponding to a limiting factor of 3.3 times within an acting time of up to 1 s

The effect of superplasticizers on the workability and compressive strength of concrete made with fine recycled concrete aggregates

The reuse of structural concrete elements to produce new concrete aggregates is accepted as an alternative to dumping them and is favourable to the sustainability of natural reserves. Even though the construction sector is familiar with the use of coarse recycled concrete aggregates, the recycled concrete fines are classified as less noble resources. This research sets out to limit the disadvantages associated with the performance of concrete containing fine recycled concrete aggregates through the use of superplasticisers. Two types of latest generation superplasticisers were used that differ in terms of water reduction capacity and robustness, and the workability, density and compressive strength of each of the compositions analysed were then compared: a reference concrete, with no plasticisers, and concrete mixes with the superplasticisers. For each concrete family mixes with 0%, 10%, 30%, 50% and 100% replacement ratios of fine natural aggregates (FNA) by fine recycled concrete aggregates (FRA) were analysed. Concrete with incorporation of recycled aggregates was found to have poorer relative performance. The mechanical performance of concrete with recycled aggregates and superplasticisers was generally superior to that of the reference concrete with no admixtures and of conventional concrete with lower performance superplasticisers

Modeling and experiment of the current limiting performance of a resistive superconducting fault current limiter in the experimental system

In this paper, a 220-V resistive superconducting fault current limiter (SFCL) prototype is built and tested under different prospective fault currents, which vary from 0.8 to 7.4 kA. A 2D superconductor model is integrated into an experimental circuit model in COMSOL to simulate the performance of the SFCL prototype in the experimental system in fault tests. In the simulation, a new E-J relationship is proposed to enhance the convergence of calculation. Comparison between simulation results and experimental results shows that the proposed model performs well in simulating current limiting performance of SFCL in experimental system in case of fault.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Genetic deficiency or pharmacological inhibition of miR-33 protects from kidney fibrosis

Previous work has reported the important links between cellular bioenergetics and the development of chronic kidney disease, highlighting the potential for targeting metabolic functions to regulate disease progression. More recently, it has been shown that alterations in fatty acid oxidation (FAO) can have an important impact on the progression of kidney disease. In this work, we demonstrate that loss of miR-33, an important regulator of lipid metabolism, can partially prevent the repression of FAO in fibrotic kidneys and reduce lipid accumulation. These changes were associated with a dramatic reduction in the extent of fibrosis induced in 2 mouse models of kidney disease. These effects were not related to changes in circulating leukocytes because bone marrow transplants from miR-33–deficient animals did not have a similar impact on disease progression. Most important, targeted delivery of miR-33 peptide nucleic acid inhibitors to the kidney and other acidic microenvironments was accomplished using pH low insertion peptides as a carrier. This was effective at both increasing the expression of factors involved in FAO and reducing the development of fibrosis. Together, these findings suggest that miR-33 may be an attractive therapeutic target for the treatment of chronic kidney disease

Performance Of Modular Sfcl Using Rebco Coated Conductor Tapes Under Repetitive Overcurrent Tests

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Recently, the REBCO coated conductor tapes have shown great improvement in the critical current value along with excellent thermal and mechanical properties, turning it more cost attractive to develop superconducting fault current limiters (SFCLs). In spite of these evolutions on the I-c and n-index values, the effect of inhomogeneity on long tape lengths must be investigated, in particular, for application in resistive-type SFCLs where several hundredmetersmust be used for 15-kV voltage level units. The degradation or irreversible damage in REBCO tapes assisted by an optimized external shunt resistor was investigated on 12-mm-width tapes submitted to repetitive overcurrent tests. A modular unit with six stacks of 0.7-m-length tapes was built and tested by applying repetitive overcurrent during 80 ms, with recovery time intervals from 1 to 3 s (under load and no-load conditions), for prospective current levels from 0.8 to 3 kA, with the limiting factor of 1.7 and 3.2. The resistive type of SFCL, which is assisted by external shunt protection, indicates reliable operating conditions after 100 tests with the fault current level of 3 kA.263Companhia Paulista de Forca e Luz (CPFL)CNPqConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Fault current test of a bifilar Bi-2212 bulk coil

A bifilar Bi-2212 bulk coil with parallel shunt resistor was tested under fault current condition using a 3 MVA single-phase transformer in a 220 V-60 Hz line achieving fault current peak of 8 kA. The fault current tests are performed from steady state peak current of 200 A by applying controlled short circuits up to 8 kA varying the time period from one to six cycles. The test results show the function of the shunt resistor providing homogeneous quench behavior of the HTS coil besides its intrinsic stabilizing role. The limiting current ratio achieves a factor 4.2 during 5 cycles without any degradation

Projeto de fundações e estruturas de um edifício destinado a uma igreja

Trabalho de Projeto para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização em EstruturasA execução deste trabalho consiste na elaboração das diferentes fases de um projeto de fundações e estrutura, neste caso destinado a uma Igreja, desde a sua conceção inicial, até à fase final de dimensionamento. Assim, são percorridas diversas etapas, iniciandose pela interpretação correta do projeto arquitetónico, de modo a possibilitar conceber a solução estrutural mais adequada. Segue-se o pré-dimensionamento dos elementos estruturais, a análise de toda a estrutura para as diferentes ações, bem como o respetivo dimensionamento, onde se destacam as secções pré-esforçadas. Para o desenvolvimento deste documento, foram essenciais os conhecimentos teóricos adquiridos ao longo do respetivo curso. Sendo um facto que os programas de cálculo automático constituem uma ferramenta de extrema utilidade para a análise de estruturas no panorama da engenharia de estruturas atual, foi naturalmente utilizado um programa de cálculo tridimensional de elementos finitos – o SAP 2000 – onde foi desenvolvido o modelo da Igreja proposto, com a finalidade de analisar estática e dinamicamente o seu comportamento. Porém, é sempre necessária a utilização dos métodos tradicionais, para o prédimensionamento estrutural, o dimensionamento das secções pré-esforçadas e para a interpretação dos resultados obtidos através do programa de cálculo automático, visto ser importante a existência de um espírito critico a quando da sua leitura. Ao longo de todo o trabalho, são enunciadas as regulamentações que se encontram em vigor e que foram utilizadas para a verificação doscritérios gerais de dimensionamento.Abstract: The execution of this work consists in the development of the different phases of a project aiming the foundations and structure of a Church, from its initial conception to final design phase. Accordingly, several steps are covered, starting with the correct interpretation of the architectural project, in order to allow the design of the most appropriate structural solution. Following, the preliminary design of the structural elements, the analysis of the entire structure to the different actions as well as the respective scaling, which highlights the sections prestressed. To develop this document, theoretical knowledge acquired during the respective course was essential. The fact that automatic calculation programs are an extremely useful tool for the analysis of structures in the panorama of current structural engineering, naturally, a program for calculating three-dimensional finite element was used - SAP 2000 - where the proposed Church model was developed in order to analyze its static and dynamic behavior. Yet, the use of traditional methods for structural preliminary design, the design of prestressed sections and the interpretation of results obtained using the automatic calculation program is always necessary, since it is important the existence of a critical spirit when reading them. Throughout this work, the current regulation are mentioned and were used for the verification of the general dimensioning criteria

Recovery tests of an hybrid current limiter composed of a SFCL in parallel to an air-core power reactor

The resistive-type superconducting fault current limiters (RSFCL) prototypes using YBCO-coated conductors have shown current limitation for medium voltage class applications for acting time up to 80 ms. By connecting an air-core reactor in parallel with the RSFCL, thus making an hybrid current limiter, one can extend the acting time for up to 1 s. In this work, we report the performance of a hybrid current limiter subjected to an AC peak fault current of 2 kA during 1 s for which within the first 80 ms the SFCL limits the current concurrently with the air-core reactor, and for the remaining 920 ms, only the air-core reactor limits the current. In order to evaluate the actual conditions for subsequent reconnection of RSFCL to the power grid, the hybrid fault current limiter was tested varying the time interval for recovery from 900 ms and 1.2 s, followed again by the concurrent operation of the hybrid limiter during 1 s (SFCL during 80 ms). From this evaluation test, the recovery time can be measured and compared using the voltage peak generated in superconducting module from the first and second fault test. The recovery time was also determined through the pulsed current method (PCM) on short-length sample test. The results showed that the fault current was limited from 1.9 kA down to 514 A after 1 cycle of 60 Hz frequency, with recovery time lower than 1.2 s for two subsequent fault current tests2869169

Electrical and Magnetic Characterization of BSCCO and YBCO HTS Tapes for Fault Current Limiter Application

Several high temperature superconductor (HTS) tapes have been developed since the late eighties. Due to the new techniques applied for their production, HTS tapes are becoming feasible and practical for many applications. In this work, we present the test results of five commercial HTS tapes from the BSCCO and YBCO families (short samples of 200 mm). We have measured and analyzed their intrinsic and extrinsic properties and compared their behaviors for fault current limiter (FCL) applications. Electrical measurements were performed to determine the critical current and the n value through the V-I relationship under DC and AC magnetic fields. The resistance per unit length was determined as a function of temperature. The magnetic characteristics were analyzed through susceptibility curves as a function of temperature. As transport current generates a magnetic field surrounding the HTS material, the magnetic measurements indicate the magnetic field supported by the tapes under a peak current 1.5 times higher than the critical current, I(c). By pulsed current tests the recovery time and the energy/volume during a current fault were also analyzed. These results are in agreement with the data found in the literature giving the most appropriate performance conductor for a FCL device (I(peak) = 4 kA) to be used in a 220 V-60 Hz grid