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After about two decades of intense research since the discovery of high-temperature superconductivity (HTSC) in cuprates, although many aspects of the physics and chemistry of these cuprate superconductors are now well understood, the underlying pairing mechanism remains elusive. Magnetism and superconductivity are usually thought as incompatible, but in number of special materials including HTSCs these two mutually excluding mechanisms are found to coexist. The presence in a system of superconductivity and magnetism, gives rise to a large number of interesting phenomenon. This article provides perspective on recent developments and their implications for our understanding of the interplay... 

Utilization of superconducting equipment increases every day due to availability of the HTS tapes with reasonable prices, commercially. Since 1997, many high-temperature superconducting (HTS) transformers have been designed and fabricated. In this paper, all the different developments of HTS transformer windings since 1997 will be reviewed. Additionally, the advantages and disadvantages of the application of the two main winding types (the pancake and the layer) in the HTS transformer will be studied. © 2020, Springer Science+Business Media, LLC, part of Springer Nature  

Growing interest in high-temperature superconducting (HTS) power devices is the result of commercial availability of the HTS tapes. One of the most promising applications of the HTS technology is HTS transformer. Flux diverters are used for critical current elevation in HTS transformer windings. In this paper multilayered flux diverter arrangements have been introduced to reduce weight and losses of conventional solid flux diverter arrangement. Horizontal and vertical multilayered arrangements have been investigated and compared with solid arrangement. Two dimensional (2D) finite element method (FEM) simulations have been used for comparison between different arrangements  

The appealing advantages of high-temperature superconducting (HTS) power transformers over conventional ones have attracted transformer manufacturing companies, power companies, research institutes, and universities worldwide to conduct research and development in this field. Unfortunately, HTS transformers are more vulnerable to mechanical stresses than conventional transformers. The results of the interaction between current carrying windings and leakage magnetic fluxes are the electromagnetic forces, which act on transformer windings. Under short circuit events, these forces are remarkable, and, therefore, catastrophic failure of transformer may arise. Flux-diverter applications have been... 

High-temperature superconducting (HTS) transformers have a promising feature in reduction of total weight, total size, and the losses of large-scale distribution transformers. However, the lower leakage reactance of HTS transformers results in a higher short-circuit fault currents and electromagnetic forces. Therefore, optimization of short-circuit electromagnetic forces is one of the crucial aspects in the design of HTS transformers. In this paper, a novel analytical method is proposed for determination of optimum distributive ratios resulting in minimization of these forces for asymmetrical multi-segment windings of an HTS transformer. Employing these distributive ratios, radial and axial... 

High-temperature superconducting (HTS) transformers have remarkable appealing advantages over conventional ones. But higher brittleness of HTS windings with respect to copper windings makes HTS transformers more vulnerable in short circuit and inrush current situations. During tap changer operation, appreciable asymmetry and non-uniform distribution of ampere-turn along the windings causes high axial component of short circuit forces and makes the situation more severe. In this paper, multi-segment winding method is employed for reduction of axial short circuit forces. An analytical method is presented for calculation of axial component of short circuit forces under tap changer operation.... 

High-temperature superconducting (HTS) transformers have a promising feature in reduction of total weight, total size, and the losses of large-scale distribution transformers. However, the lower leakage reactance of HTS transformers results in a higher short-circuit fault currents and electromagnetic forces. Therefore, optimization of short-circuit electromagnetic forces is one of the crucial aspects in the design of HTS transformers. In this paper, a novel analytical method is proposed for determination of optimum distributive ratios resulting in minimization of these forces for asymmetrical multi-segment windings of an HTS transformer. Employing these distributive ratios, radial and axial... 

Presence of defects, conducting particles, nonconducting particles, and nitrogen gas bubbles in the insulation system of high-temperature superconducting (HTS) transformers, mainly inside the liquid nitrogen as its major insulation, can create local field enhancement and consequently partial discharges which eventually lead to the catastrophic failure of the transformer. In this paper, two-dimensional (2D) axisymmetric finite element method (FEM) modeling via COMSOL Multiphysics software has been utilized for the investigation of the impact of size and shape of conducting particles and nitrogen gas bubbles on partial discharge (PD) activities in liquid nitrogen. Conducting particles of... 

Mitigation and control of leakage fluxes and short circuit forces needs much more attention, for a high-temperature superconducting (HTS) transformer, than for a conventional one. Different methods such as the application of auxiliary windings, multi-segment winding, and flux diverter have been presented in the literatures for leakage magnetic field reduction in HTS transformers. In this paper, for the first time, optimal design of auxiliary windings has been performed for a 132/13.8 kV, 50 MVA three phase core type HTS transformer. Genetic algorithm (GA) has been used for the optimization process. Induced current in auxiliary windings which is inversely proportional to the leakage fluxes... 

Appealing advantages of high-temperature superconducting (HTS) transformers are very promising for the contemporary and future power delivery systems. Cryogenic insulation technology is one of the key technologies for their commercialization. In this paper insulation design of the end part of cryogenic high voltage (H. V.) bushing of a 230/20 kV HTS transformer is developed. Analytical relations and finite element method (FEM) modelling, through application of COMSOL Multiphysics software, are employed for determination of electric field distribution in this design process. Weibull 0.1% dielectric breakdown strength has been considered as criterion for insulation design. Different shape and... 

High-temperature superconducting (HTS) transformers with multi-segment windings have been proposed in earlier literatures for the hysteresis loss reduction and short circuit electromagnetic force mitigation. The optimum distributive ratios for these multi-segment windings have been determined in earlier literatures. Asymmetrical seven segment winding with its optimum distributive ratio (k = 1/12) results in minimization of short circuit electromagnetic forces under normal tap and any adjusted tap. However, insulation design and leakage inductance calculation for the multi-segment winding of an HTS transformer have not been addressed in past literatures. Insulation design is one of the most... 

Josephson junction in superconductor circuits and metamaterials is modeled as a tunable inductance. The Josephson inductance is tunable by the bias current passing through it and can be tuned from an initial value to a very large value as much as one can push bias current near the critical current but not exceeding it. Tunability by bias current allows design of programmable metamaterials with flexible functions in microwave regime. In High-Temperature Superconductivity (HTS) tunable metamaterials, Josephson junctions should be used in series configuration to give usable tunable inductance. Each Step-Edge Josephson junction (SEJs) in HTS has a critical current that is dependent on its... 

Josephson junction in superconductor circuits and metamaterials is modeled as a tunable inductance. The Josephson inductance is tunable by the bias current passing through it and can be tuned from an initial value to a very large value as much as one can push bias current near the critical current but not exceeding it. Tunability by bias current allows design of programmable metamaterials with flexible functions in microwave regime. In High-Temperature Superconductivity (HTS) tunable metamaterials, Josephson junctions should be used in series configuration to give usable tunable inductance. Each Step-Edge Josephson junction (SEJs) in HTS has a critical current that is dependent on its... 

The application of flat superconductor rings has been investigated in the structure of inductive shield-type high temperature superconducting fault current limiters, HT c-SFCL. A laboratory scale inductive shield-type HT c-SFCL has been designed and fabricated using flat superconductor rings. The fabrication process has been fully presented. YBCO powder has been used for the fabrication of superconductor rings. This fabrication process, being quite innovative, is introduced completely. The method of the trapped field measurement has been used for the critical current density measurement of the fabricated superconductor rings. The device with nominal current of 2 A was tested in a 30 V... 

Distributed power generation and the ever-growing load demand have caused fault current levels to exceed the nominal rating of the power system devices, and fault current limiters are more needed. Superconducting fault current limiter (SFCL) forms an important category of current limiters. In this paper, a novel flux-based model for the inductive shield-type high-temperature SFCL is developed based on the Bean model. This model is employed to simulate the SFCL performance in a sample circuit. Utilizing the model, the signal characterization of the limited current is determined. A prototype laboratory scale SFCL has been fabricated with superconducting rings. Yttrium barium copper oxide... 

Discovery of superconductivity in the impurity band formed by heavy doping of boron into diamond (C:B) as well as doping of boron into silicon (Si:B) has provided a rout for the possibility of new families of superconducting materials. Motivated by the special role played by copper atoms in high temperature superconducting materials where essentially Cu d orbitals are responsible for a variety of correlation induced phases, in this paper we investigate the effect of substitutional doping of Cu into diamond. Our extensive first principle calculations based on density functional theory which are averaged over various geometries indicate the formation of a mid-gap band, which mainly arises from... 

In search of finding the dominant mechanism in high temperature superconductivity phenomena, the Y3Ba5Cu8O18 compound was synthesized through the standard solid-state reaction technique. Characteristic XRD experiment was performed on the samples and was analyzed by the MAUD software refinement program. The analysis results indicate a 358 phase structure with the initial nominal stoichiometry. The electrical resistivity and its behavior under different magnetic field were measured. The electrical resistivity indicates the transition temperature Tc onset = 102 K with transition width ΔTc = 2.4 K. This is the first observation of such a high transition temperature in the Y-based compound.... 

Josephson junction in superconductor circuits and metamaterials is modeled as a tunable inductance. The Josephson inductance is tunable by the bias current passing through it and can be tuned from an initial value to a very large value as much as one can push bias current near the critical current but not exceeding it. Tunability by bias current allows design of programmable metamaterials with flexible functions in microwave regime. In High-Temperature Superconductivity (HTS) tunable metamaterials, Josephson junctions should be used in series configuration to give usable tunable inductance. Each Step-Edge Josephson junction (SEJs) in HTS has a critical current that is dependent on its...