High-temperature Superconducting Element Research Articles

Influence of cooling conditions of HTS assembly on the characteristics of a moving maglev system

Background: analysis of the influence of cooling conditions of high-temperature superconducting elements on the power characteristics of a maglev system under conditions of rapidly changing magnetic fields
 Aim: analysis of the influence of cooling conditions of high-temperature superconducting elements on the force characteristics of a magnetic-levitation transport platform under conditions of rapidly changing magnetic fields caused by the inhomogeneity of the magnetic track.
 Methods: numerical analysis of the maglev system was performed by the finite element method in the Comsol Multiphysics engineering simulation software.
 Results: at fast, more than 5 T/s, magnetic field change rates, due to the motion of the superconductor in a magnetic field with a non-uniform local distribution, the preferred method of cooling is the use of cryocooler technology. At rates of change of the magnetic field less than 5 T/s, it is permissible to use liquid nitrogen as a cooler.
 Conclusion: The developed numerical model makes it possible to predict the dynamic characteristics of levitation systems of various scales and can be applied to contactless transport, as well as in rotating machines, including kinetic energy storage devices.

Simulation of a Low-Voltage Direct Current System Using T-SFCL to Enhance Low Voltage Ride through Capability

Owing to the increasing penetration level of distributed energy resources (DER) and direct current (DC) load, the usage of low-voltage direct current (LVDC) systems has expanded to achieve efficient operations. However, because the LVDC system reaches the peak fault current at a faster rate than the alternating current (AC) system, a solution that protects the system components is necessary to maintain system integrity. It is required by the low-voltage ride-through (LVRT) that the DERs maintain their interconnections with the LVDC system and support fault recovery. In this study, a method is proposed to allow the application of the superconducting fault current limiter (SFCL) to reduce the fault current and enhance the LVRT capability. However, when the DER maintain a connection to support fault recovery, the conventional resistive-type SFCL must withstand the burden of high-temperature superconducting (HTSC) operation during fault state dependence on LVRT. Therefore, this study proposes a trigger-type SFCL to reduce the burden of the HTSC element and enhance the LVRT capability. The voltage sag related to the LVRT was improved owing to the SFCL. The proposed solution was confirmed using PSCAD/EMTDC, which is a commercial software.

Power consumption and cumulative energy of bridge type SFCL with simultaneous quench

A bridge type superconducting fault current limiter (SFCL) with two high-temperature superconducting (HTSC) elements using flux-coupling is proposed to reduce the influence of short-circuit accidents. A laboratory-scale prototype SFCL was fabricated and short-circuit test was conducted. The power consumption and the accumulated energy were compared and analyzed according to the winding current when the number between N1 and N2 coil changed during the fault period. In addition, the operating range of the flux linkage and the variation of the magnetizing force area were compared according to the magnetizing current. The usefulness of the proposed SFCL was confirmed through analysis of the fault current limiting operation characteristics and the energy consumed by the simultaneous quench of two HTSC elements. As a future study, we will apply this modified bridge-type SFCL model to a direct current (DC) distribution system. First, after establishing a DC short circuit accident test environment, this SFCL is constructed in front of the DC load and the fault occurrence resistor to measure and analyze the DC fault current limiting characteristics.

Твердотельные магнитные материалы для магнито-левитационного транспорта.

Study and implementation of innovative systems of environmentally friendly and energy-efficient transport based on magnetic levitation, the principle of operation of which is based on the use of new solid-state magnetic materials based on compounds of rare earth materials, in particular materials with high-temperature superconductivity based on Y, permanent magnets based on Nd and Sm and magnetocaloric alloys based on Dy, Tb are of great interest throughout the world. In this work, the basic principles of magneto-levitation transport with the most economical principle of acceleration and deceleration - gravitational - are studied experimentally on mock-ups. The strength characteristics were measured: the levitation force and the lateral stabilization force, as well as losses during periodic translational motion of a cryostat with high-temperature superconducting elements made of ceramic material Y-Ba-Cu-O over the paths of permanent magnets made of the rare-earth compound Nd-Fe-B. A system for measuring the speed and compensation of losses for the implementation of continuous motion has been created and tested. The presented results indicate the possibility of scaling the layout project. It is concluded that the investigated scheme may be of practical interest for intracity and local transport communication with high comfort, environmental friendliness and record economy in the case of a successful solution of the problem of cooling HTSC elements to the temperature of the phase transition to the superconducting state, for example, using new principles of solid-state magnetic cooling based on compounds Dy-N, Tb-Ni, etc.

Уменьшение магнитных потоков рассеяния в линейных генераторах Вернье с помощью высокотемпературных сверхпроводящих элементов

The article presents the results of studies aimed at improving the power performance indicators of linear electric generators for wave power plants by reducing the flux leakages using high-temperature superconducting (HTS) inserts placed in between the teeth. The generator design involving application of the Vernier principle for magnetic flux modulation with a translator in the form of a hollow cylinder is considered. Generators of this type are used in float wave power plants driven directly by a reciprocating float, which transmits large forces at a low motion speed. The calculations were carried out using the HTS properties modeling procedure based on representing the currents induced in a superconductor in the form of magnetic moments of these currents, which made it possible to simplify the analysis of the electromagnetic field in the generator without significant additional errors. As a result, the characteristics of the electromagnetic force longitudinal components and phase winding flux linkages versus the translator displacement have been obtained. The use of HTS inserts and a distributed winding in the stator made it possible to reduce the electromagnetic leakage losses and increase the interaction force between the stator and translator. However, since the additional outlays for the cooling system and thermal insulation of the HTS elements are commensurable with the generator cost, the obtained results on improving the power performance parameters do not allow an unambiguous statement to be made about the effectiveness of the considered technical solutions.

Analysis on Operational Characteristics of Double Quench Flux Lock Type Superconducting Fault Current Limiter

The superconducting fault current limiter (SFCL) which has many advantages is being chosen as an attractive method for limiting fault current. To upgrade the performance of the SFCL, various configurations are reported. Among them, the double-quench type SFCL has been studied in order to reduce the power burden of the high-temperature superconducting (HTSC) elements. The double-quench type SFCL which consists of the two HTSC elements and the normal resistance is a method to improve the performance of the HTSC elements. The design of the normal resistance in the double-quench type SFCL for the control of distributed fault currents on both HTSC elements to reduce the power burden is very important. However, the double-quench type SFCL is difficult to change the specification of the component depending on changing the power system. To improve the disadvantage on the double-quench type SFCL, this paper proposed the double-quench-flux-lock type SFCL which combine the double-quench type SFCL and the flux-lock type SFCL. The conventional flux-lock type SFCL which consists of an iron core, two coils, and the HTSC element could control the operation current and the impedance of the SFCL depending on the turn ratio between two coils. The operational characteristics of the flux-lock type SFCL could flexibly respond to changes in the power system. The double-quench-flux-lock type SFCL proposed in this paper was verified through PSCAD/EMTDC.

Magnetizing Characteristics of Bridge Type Superconducting Fault Current Limiter (SFCL) with Simultaneous Quench Using Flux-Coupling

A bridge type superconducting fault current limiter (SFCL) with simultaneous quench using two high-temperature superconducting (HTSC) elements and two coils was fabricated to analyze the fault current limiting characteristics. Before and after the fault occurrence, the current limiting operation and the voltage waveforms of each device were compared according to the change of the input voltage. We also analyzed flux linkages and instantaneous powers of the bridge type SFCL with simultaneous quench using flux-coupling composed of HTSC elements with different critical currents. During the fault period, the magnetization power area and the flux linkage’s operating range variation due to the magnetizing current were compared with each other.

Fault Current Limiting Characteristics of a Small-Scale Bridge Type SFCL with Single HTSC Element Using Flux-Coupling

In this paper, a bridge type superconducting fault current limiter (SFCL) with a single high-temperature superconducting (HTSC) element is proposed to allow fault current limiting operation in direct current (DC) conditions. First, the principle of operation of the bridge type SFCL with a single HTSC element using flux-coupling was presented. After the fault occurrence, the fault current limiting operation and voltage characteristics, the power load characteristics of each device, and the energy consumption of the two coils and the HTSC element were analyzed in the proposed SFCL. As a result, it is confirmed that in the case of the additive polarity winding, the power consumption and the energy consumption of the HTSC element were lower than those in the subtractive polarity winding, and the fault current limiting characteristics were excellent.

Modeling the Heating in a High Temperature Superconducting Current Carrying Element in Fault Current Limiters

Mathematical model was developed for modeling the increase temperature in high temperature superconducting (HTS) current carrying element in superconducting fault current limiters (SFCL). The variation in the heating up of HTS element along its length is a result primarily of the variation in its resistance that has to do with the manufacturing process employed to make it.The model was developed and mathematical modeling of the process was carried out in the Comsol MultiPhysics software package. Element that was tested was a 12 mm wide stack of three stainless steel tapes and three HTS soldered to each other. In order to get more precise parameters for the models the cross-sectional thermal conductivity was measured for the stacks of HTS of two different types. The estimates obtained using the model were very close to experimental data. The impact was also studied of the spread of the electrical resistance of HTS on how fast the current carrying element made from it heated up.

Magneto-Thermal Coupling Design and Performance Investigation of a Novel Hybrid Superconducting Fault Current Limiter (SFCL) With Bias Magnetic Field Based on MATLAB/SIMULINK

Energy demand is growing rapidly worldwide, and sustainable solutions are required to improve the energy supply. The new devices like high-temperature superconducting fault current limiters (SFCLs) are popular in recent years. They use the electrical properties of high-temperature superconductivity to instantaneously protect power grids against short circuits and thereby prevent costly outages. They can not only reduce the capacity of the circuit breaker but also lower the cost of line construction. They have become much promising for application in a high-voltage transmission line. A novel hybrid SFCL with a bias magnetic field is proposed by combining a reactor with double-split symmetrical windings and a non-inductive high-temperature superconducting (HTS) magnet, which is in series to one branch of the reactor. An electro-magnetic model of the reactor and a magneto-thermal coupling model of the non-inductive HTS element have been built, and the simulation model of this SFCL is developed in MATLAB/SIMULINK. Its performance is investigated through the simulation considering a serious short-circuit fault and is compared to the performance without SFCL. The results validated the effectiveness of this kind of hybrid SFCL.

Construction of combined models of the properties of bulk high-temperature superconducting materials

The article contains the results of research that was aimed at improving the models of properties of bulk high-temperature superconducting (HTS) materials, which are necessary for numerical analysis of electromagnetic fields in electrical devices containing elements of high-temperature superconductors. Approximating combined models for a set of transport and bound currents are considered, which are determined, respectively, by the resistive model for currents and the nonlinear hysteresis model for the magnetization. The model of transport currents is based on the known types of the critical-state model. The material-magnetization model is composed for a set of magnetic moments of elementary superconducting cylinders with diameters that are much smaller than their length, which are oriented in the direction of the principal anisotropy axis of the material. The approximation to the actual conditions is realized by the statistical characteristics that specify the possible changes in the critical current density, the critical field strength, and the spatial orientation of the basic axes of the elementary cylinders. The results of studies of a laboratory model, which consists of a cylindrical HTS element and an annular permanent magnet, are presented and compared with the results of electromagnetic-field calculations according to the proposed models of properties.

Reflective Power Limiter for X-Band With HTSC Switching Element

This paper presents a new type of power limiter (PL), using superconducting-to-normal state phase transition in high-temperature superconductor. The presented device differs from the existing ones mainly in the reflective principle of its operation. In fact, the PL is a three-resonator microstrip filter, whose resonators are configured and arranged in such a manner that coupling coefficient between the outer resonators is equal to zero and the inner one has a gap in the middle section shunted by a high-temperature superconducting (HTS) film element. In small-signal mode, the HTS element is in low-loss state, and the device is essentially a three-pole filter with low transmission loss. When the level of the signal exceeds the threshold, the HTS element transits to the high-loss state, and the Q-factor of the inner resonator falls, breaking the coupling in the structure. This leads to the corresponding increase in the PL's transmission loss due to reflection. The higher the level of incoming power, the more the Q-factor falls. The PL operating frequency is 8 GHz with 8.5% fractional bandwidth. It remains operable up to 40 W of input power, providing 38-dB limitation.

Analysis on Operating Characteristics of a Double Quench SFCL with a Transformer

An SFCL(Superconducting Fault Current Limiter), which has zero impedance characteristic, doesn"t have power loss and limits fault current quickly, therefore it plays a rule as a protective equipment. And there are many types of SFCLs. In this paper, we analyzed operating characteristics of a double quench SFCL with a transformer. When a fault current flows on this SFCL, a HTSC(High Temperature Superconducting) element on primary of the transformer is operated and then a HTSC element on secondary of the transformer is operated. We tested this SFCL according to turn ratio and compared a double quench SFCL with series resistance for the SFCL with a transformer. After experiments, we could confirm fault current limiting characteristics of the SFCL with a transformer according to turn ratio. Also operating characteristics and power burden of HTSC element according to application for series resistance and for transformer were verified.

Electromechanical energy conversion in a system with a bulk high-temperature superconductor. Part 2. Device operation analysis

The operation of a linear electromechanical vibration device with a part made of a high-temperature superconducting (HTS) material is analyzed. Converter models considered in the first part of this paper [1] are used in the calculations. The parameters of the model of HTS material properties are determined by comparison of the data obtained by calculations and by experimental investigations of force interactions in the laboratory device model. Functions of flux linkage and current force in the coil and permanent magnet movements are calculated for a macroscopic model based on analysis of the electromagnetic field. The calculation results of the operation parameters of the electromechanical converter are shown in the form of amplitude-frequency characteristics of the current in the coil, the permanent magnet movement amplitude, and electrical and mechanical power. Dependences of powers, efficiency, and current phase on the active mechanical load on the resonant frequency are determined. The obtained characteristics are compared with simulation data of a similar converter without the HTS element. It is concluded that the HTS elements significantly change the parameters of the conversion of electrical energy into mechanical energy. It is shown that the electromechanical converters with bulk HTS elements can be more efficient than converters of traditional design.

Electromechanical energy conversion in a system with a bulk high-temperature superconductor. Part 1. Mathematical simulation of processes

Features of energy conversion in the linear electromechanical vibration device with an element made of high-temperature superconducting (HTS) material are considered. A disk-shaped permanent magnet with axial magnetization moves inside a fixed circular coil, and a ceramic HTS element, also disk-shaped, is fixed at a distance from the permanent magnet. All converter elements are arranged coaxially. The HTS element transitions into a superconducting state in the magnetic field of the permanent magnet. The purpose of the investigation is to find the effect of the HTS element effect on the static and dynamic parameters of the converter by comparing the operation of the device with the HTS element and without it. Mathematical models are developed for the calculation of dynamic characteristics of the device in the Matlab/Simulink software environment for electrical and mechanical subsystems. The connection between the subsystems is defined by functions of flux linkage of the coil and the electromagnetic force, which are obtained by the analysis of the electromagnetic field by the method of spatial integral equations taking into account HTS material properties. A combined model of HTS material properties is proposed with two sources of magnetic fields (magnetization and current density), which is more universal than current only models.

Limitation of Fault Current and Burden of Superconducting Element Applied to Neutral Line of the Transformer

The consumption of electrical energy has been increased since industrial revolution and still increasing so far. As the consumption of electricity increases, the problem of the failure of electric device and degrading of electric reliability by over current from the related fault happened. Therefore, the research of electrical device using high-temperature superconducting element is going on now and superconducting fault current limiter (SFCL) was applied on the neutral line of common transformer. As the applied voltage increases, the characteristics of the electrical power burden of SFCLs were studied. In case of fault in the power system, superconducting element restricted the fault current by normal conductivity element connected in third winding of a transformer. As a result of the test, it was confirmed that the conduction element limited initial fault current promptly as the voltage increases. After this, the conduction element took the power burden of fault current by changing the way of current and the limit rate became high as well. Also, it was confirmed that the power burden of conduction element was reduced due to no change of limit rate of fault current. By adapting of the SFCL to neutral line of a transformer and of normal conduction element to power system in the third winding, the use of current protection facility became available without increase and change of the capacity. Accordingly, the current limiter which was applied on the neutral line of a transformer was considered to have effects of cost saving, preventing mechanical failure and expansion of fault.

송전급 초전도한류기의 적용에 따른 선로보호용 비율전류차동계전기의 동작특성 및 보호협조 분석

The fault current of the power transmission system is greater than that of the power distribution system. Therefore, the introduction of superconducting fault current limiter (SFCL) is more needed to reduce the increased fault current. The trigger-type SFCL consists of the high-temperature superconducting element (HTSC), the current limiting reactor (CLR) and the circuit breaker (CB). The trigger-type SFCL can be used to supplement the disadvantages of the resistive-type SFCL. The operation characteristics of the current ratio differential relay which is usually applied to the protection device of the power transmission system are expected to be affected under fault conditions and the applicability of the trigger-type SFCL. In this paper, we analyzed the operating characteristics, by the fault conditions, between the current ratio differential relay for line protection and the trigger-type SFCL in the power transmission system through the PSCAD/EMTDC simulation.

Intermediate Joint of Current Lead in Conduction-Cooled Superconducting Magnet System

The semi-retractable current lead is composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and a high-temperature superconducting element, conducting the current down to liquid helium temperature. The normal metal element is disengaged from the high-temperature superconducting element through the multicontact connector without disturbance to the insulating vacuum space and without requiring complete removal of the normal metal element. The current lead is applied into the conduction-cooled superconducting magnet system developed by ourselves. The intermediate joint with a lockable set point is thermally connected to the first-stage of a cryocooler and carries current through a strip of louvered material. The performance of current lead is investigated with respect to the electrical contact resistance during the magnet charging process. The effects of current level and operating temperature on the heat generation in the intermediate joint are also discussed.

An Effect of HTS Wire Configuration on Quench Recovery Time in a Resistive SFCL

We experimentally investigated the correlation between the high-temperature superconducting (HTS) wires configuration in an HTS element and recovery time after quench in a resistive superconducting fault current limiter. The variables of the configuration are horizontal and vertical gap distances between HTS tapes in an element. Eight samples were made with different gap distances and tested. A SUS-stabilized YBCO tape with 4.4 mm width had been used in the experiment. It was cooled by LN2 in a cryostat under the pressure of 1 bar, saturated state. In the short-circuit test, the temperature of the wire's surface was measured. Recovery time of the HTS sample increased with decreasing horizontal and vertical gap distance due to stagnation of bubbles. When the gap distance was larger than a size of a bubble, the effect of gap distance was ignorable. Considering a volume and recovery time, the sample that has narrower gap distance was favorable.

3-D Numerical Analysis of the 68 kA Heat Exchanger of the ITER HTS Current Leads

High-temperature superconducting (HTS) current leads consist of a resistive and a superconducting part. The resistive part, which transfers the current from the room temperature termination to the top terminal of the HTS element, is a resistive heat exchanger cooled by cryogen gas and optimized for the specified operating conditions. This optimization requires complex analysis of multiple physical phenomena, such as Joule heating, fluid flow, and heat transfer by conduction and convection. The solution of such a problem requires a numerical approach. The paper reports on the 3-D numerical calculations made on the heat exchanger type adopted for the Large Hadron Collider HTS current leads. It consists of a central conductor with fins for increased heat transfer surface, and it is cooled by a forced flow of helium gas. The same type of heat exchanger has been adopted for the ITER HTS current leads operating at currents ranging from 10 to 68 kA. In this paper, the 3-D model of the ITER 68 kA heat exchanger is presented and discussed. In particular, the effect of the turbulence induced by the zig-zag flow of the gas between the fins is analyzed and quantified.