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Continuous improvement of fuel efficiency and reducing harmful emissions is a trend driven by economic and environmental considerations. It's primarily relevant for transport. Implementation of integrated electric propulsion (IEP), or full electric propulsion (FEP) systems is one of the ways to accomplish this. The power plant works in the rated mode as part of the electric propulsion system. Also, these systems usually include power static converters – rectifiers and inverters. The traditional power switches, based on semiconductor elements, for example, an insulated-gate bipolar transistor (IGBT), have significant heat generation and cannot be placed in the cryogenic zone of fully superconducting systems. Placing of the power static converters (rectifiers and inverters) in a warm zone increases the coolant consumption due to heat inflows into cryogenic zones with superconducting equipment through current leads. Thus, the task of creating power cryogenic switches based on other physical principles is required. This experimental research is dedicated to the determination of the recovery time of the superconducting properties of the HTS-2G tape after removing an external perpendicular magnetic field. That's necessary to estimate the possibility of its use as a superconducting switch (cryotron) for large-scale applications. Moreover, this experimental research methodology is applicable for the estimation of the current-carrying capacity and measures the operation stability in the case of large-scale superconducting devices where HTS-2G tape is in an external alternating magnetic field. [ABSTRACT FROM AUTHOR]

The high temperature superconducting (HTS) cable has shown promising prospects in megacities for the advantages of high transmission power density and low loss. However, when HTS cable is working on grid, various kinds of faults may cause irreversible damage, resulting in the failure of reclosing. In this paper, the resistive superconducting fault current limiter (R-SFCL) is introduced into the power system to cooperate with the HTS cable, so as to reduce the potential damage caused by fault current. Firstly, the equivalent circuit models are established, and then transient response of HTS cables under fault condition is analyzed, the recovery time of HTS tapes are used to define the design of R-SFCL. Finally, the operating reliability of HTS cable has been evaluated and measures about adaptive reclosing times were proposed under different fault currents. [ABSTRACT FROM AUTHOR]

The Tri-axial high temperature superconducting (HTS) cable usually subjects to the impact of the fault currents in the power system. During the fault, a large amount of the Joule heat is generated, which may be damage cable. In this paper, an analysis model of electromagnetic thermal transient characteristics of the 10 kV/1 kA cable is built. The transient characteristics of the HTS cable are analyzed under a fault current of 15 kA rms lasting 0.14 s, and the current, resistance and temperature of the HTS cable are obtained. The maximum temperature of the HTS cable is 153.1 K under fault current. Meanwhile, the safe operating range of the HTS cable under the fault current of 15 kA to 25 kA is obtained. the analysis results will provide the theoretical basis for the quench protection and relay protection strategy of the tri-axial HTS cable in the Grid. [ABSTRACT FROM AUTHOR]

Rare-earth barium copper oxide (REBCO) tape is used for resistive type superconducting fault current limiters (RSFCLs) owing to its quick response and simple structure. To shorten the recovery time, film boiling on the REBCO tape should be suppressed as it exhibits poor heat transfer performance. To address the aforementioned issue, this study utilized low thermal conductivity materials as the thermal/electrical interface material for porous-stabilized REBCO tape. The experimental results showed that the cooling and recovery performances were dramatically improved by utilizing an insulating epoxy, which has a thermal conductivity of 0.6 W/mK. Based on the visualization of the boiling behavior, the liquid-solid contact between liquid nitrogen and the REBCO tape was promoted by the insulating epoxy, in which the film boiling was easily broken. [ABSTRACT FROM AUTHOR]

The implementation of superconducting fault current limiters (SFCL) in the electrical power system requires the coordination of its parameters with the installed power system protection (PSP), in particular when using automatic reclosing (AR). The crucial parameter for AR is the recovery time of the SFCL, understood as the SFCL return time to the superconducting state after its operation. This time will depend mainly on the efficiency of the cooling system and the heat dissipation processes in the electrical insulation system. This article presents the results of experimental research on the return time to the superconducting state of superconducting tapes with layers of electrical insulation of various thicknesses. The tests were carried out in conditions in which the density of energy generated during the surge current flow correspond to the operating conditions of superconducting material in SFCL. Also, the transfer of this energy to liquid nitrogen corresponds to phenomena occurring in SFCL. The recovery time of several types of high temperature superconducting tapes in the zero current state and recovery under load were determined. The range of the load current at which it is possible return to the superconducting state was determined for tapes with and without electrical insulation. It has been shown that the analysis of these processes must take into account the strong dependence between the thermal energy transfer from the sample surface to liquid nitrogen and the type of nitrogen evaporation process on the surface of the sample. The presented research results are of particular importance for the functionality of SFCL and its cooperation with the PSP. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SFCLs) are required to return to the superconducting state within the proper time (recovery time) after limiting a fault current according to a relay operation scheme in a power system. In order to apply SFCLs to power systems, the recovery time is important property and deeply depends on the heat transfer property of the heated surface of the superconducting tape (normal conducting state) to liquid nitrogen. It has been confirmed that REBCO tapes with various shaped fins or PTFE coating improved cooling property. In this paper, to clear the mechanism of cooling property improvement of fins or PTFE coating, boiling phenomena on REBCO tapes with some types of fins or PTFE coating was observed by use of a high-speed video camera. The influence on the cooling improvement property of cooling fins and PTFE coating was discussed according to the photographical view of the boiling phenomenon. [ABSTRACT FROM PUBLISHER]

This paper analyzes the effect of a resistive superconducting fault current limiter (R-SFCL) applied to an isolated microgrid with a dynamic load model. The isolated microgrid with high penetration of distributed generators (DGs) is vulnerable to faults in aspect of frequency stability. For the more accurate analysis of the isolated microgrid, the dynamic composite load model, which consists of a static part with the constant impedance—current–power model and a dynamic part with the high-order induction motor model, is applied in this study. The R-SFCL in isolated microgrid can effectively mitigate the fault current by rapidly providing protection during the fault as well as improve the transient stability by using the fast response characteristics of the R-SFCL as a transition signal for the DG. To evaluate the performance of the proposed model, a case study is carried out by a time-domain simulation based on the DIgSILENT PowerFactory software [ABSTRACT FROM PUBLISHER]

The feasibility of a conduction-cooled \MgB2 -based superconducting fault-current limiter with fast recovery is investigated. A real-scale device for a distribution network is considered. The dc resistive configuration is chosen in order to avoid ac losses and to allow conduction cooling. A high-heat-capacity cable is specifically developed in order to cope with the requirement of fast recovery. A short-length sample of the cable is manufactured in order to assess its feasibility. The detailed design of a prototype is also carried out, and the performance is numerically investigated. [ABSTRACT FROM PUBLISHER]

Quantity of consumed electricity is increasing due to increase of population and industrial development. Consequently, fault current is increased during occurrences of faults. For restricting these fault currents, in this paper, recovery characteristics per types of faults was analyzed by applying reclosing motion to 3-phase transformer type superconducting fault current limiter. Established reclosing cycle (CO-t-cycle-CO-t-cycle) is 5-10-7-20-5 cycle. (C: Close, O: Open) Electricity burden of SFCL is different according to types of faults. So, according to turn ratio, a test was carried out with regard to fault current limit per types of faults and recovery characteristics. In single line-to-ground fault and in double line-to-ground fault, it could be confirmed that it limits electric current because fault current of fault phase provides impacts on coiling wire of different sound phase. And it was also confirmed that fault current limit rate is lowered during double line-to-ground fault instead of single line-to-ground fault. When it is triple line-to-ground fault, it was confirmed that size of fault current limit of T-phase is lower than R-phase and S-phase. In addition, it could be confirmed that size of fault current limit is lower the more transformer secondary stream turn ratio is smaller. Also, it was also confirmed that time of recovery of superconducting element became shorter in open cycle the more turn ratio per types of faults is smaller. And power consumption affecting superconducting element was related to recovery time. [ABSTRACT FROM PUBLISHER]

In order to limit fault current from an accident in power grid, many research groups have developed resistive superconducting fault current limiters (SFCLs) with a bifilar solenoid and a bifilar pancake types. Comparing with a bifilar solenoid type, a bifilar pancake type has the advantage of its volume, but it has problems such as recovery and insulation of SFCLs. To eliminate the drawback of these two types, in this paper, a new type of coil that is an oval-shaped SFCL, have proposed. This type consists of inner and outer layers which are connected in parallel. A small-scale sample coil was fabricated and experiments for both a short circuit test and recovery characteristic test were performed in liquid nitrogen. Experimental results were compared with two types of coils; the bifilar solenoid and bifilar pancake coil. Consequently, we confirmed the feasibility of an oval-shaped type. [ABSTRACT FROM AUTHOR]

We analysed the protective cooperation between a reclosing system and a flux-coupling type superconducting fault current limiter (SFCL). In order to compare the recovery behavior, the SFCLs without or with a neutral line between secondary coil and superconducting elements were prepared. Most of power grid has a reclosing system, which controls the circuit breaker by the sequential procedure, to cope with various faults. Generally, fast recovery of the SFCL was very important for stable operation between the reclosing system and the SFCL. The reclosing cycles (CO-t-CO-t-CO) for the experiments was set to 5-10-7-20-5. Recovery time in a flux coupling type SFCL without a neutral line was lengthened due to unequal quench between superconducting elements and it caused decrease of the maximum applied voltage. In the meantime, recovery time in the SFCL with a neutral line was shortened due to simultaneous quench between the elements. So, applied voltage of the power system could be higher within same reclosing system. As turn's ratio between secondary coil and superconducting elements was increased, recovery time was longer due to increase of their power. We confirmed that a flux-coupling type SFCL with a neutral line was more profitable for good cooperation between superconducting elements and a reclosing system. [ABSTRACT FROM AUTHOR]

Research on resistive superconducting fault current limiters (SFCLs) using coated conductor(CC) has now been advanced from development to commercialization stage. It is necessary to investigate the recovery characteristics of SFCL for effective application to power system. In Korea, if the SFCL is directly inserted to distribution power grid, it must be recovered in 0.5 s after fault. Since temperature sensor is not accurate in liquid. nitrogen bathe and temperature of CC, after falling down below 92 K, is impossible to be measured by electrical method, it is difficult to measure the temperature of SFCL during the recovery of YBCO CC. In this paper, an experimental method was proposed to determine the recovery of resistive SFCLs. Under over-current for 0.1 s, maximum temperature of high temperature superconductor (HTS) wire increased to 300 K; after a few seconds, recovery time was measured by increasing DC current. With these experiments, thermal relaxation time required for the temperature of CC to decrease to 77 K was analyzed. [ABSTRACT FROM AUTHOR]

Since resistive superconducting fault current limiters (SFCLs) are inserted to a power system directly, it is necessary to recover instantly after the clearance of a fault. Most resistive SFCLs using BSCCO bulk or thick film have a recovery time of tens of seconds. An SFCL using YBCO coated conductor (CC) has a large surface area contacted to liquid nitrogen. Joule heat flux of the SFCL is smaller than that of other types when a fault occurs. Therefore, it is important for the SFCL employing CC to investigate a recovery time. In this paper, the recovery characteristics of SFCL with respect to applied voltage were analysed in a power system. All tests were performed in liquid nitrogen and sub-cooled nitrogen. From this result, the parameters for recovery time were obtained. [ABSTRACT FROM AUTHOR]

It is necessary for an SFCL to recover quickly after fault removal to ensure power system stability. Resistive type SFCLs have been considered to return more slowly to superconducting state after fault removal compared with other types of SFCL due to the heat generated during the operation. Then, it is necessary to investigate the recovery time in detail to design an SFCL. This paper describes the recovery time characteristics of an SFCL using Y123 thin film. The recovery time has been measured under various conditions. The parameters are the operating duration, amplitude of the current, and resistance of the parallel resistor. From the results, recovery time is proportional to these three parameters. In addition, it is shown that the parallel resistor plays a role in adjusting the recovery time. [ABSTRACT FROM AUTHOR]

To select electrical insulator (insulator) between coated conductor tapes (CC tapes) of two parallel non-inductively wound solenoid type superconducting fault current limiter (SFCL) is a important issue. Insulator is inserted for separation of two parallel tapes. Quench characteristics and recovery time of SFCL are related on insulator and thermal contact condition. Insertion of tape-shape insulating materials is a normal way of insulation for non-inductively wound SFCL. Thus, various tape-shape insulating materials can be the insulator of SFCL. In this paper, sample holder to simulate parallel tapes with various insulators was fabricated, and sticky polyimide tape and insulating paper tape were chosen for insulator of samples. Short-circuit test was performed in the same condition except inserted insulator of samples. Quench characteristic, generation of resistance, and recovery time of each sample were compared to the others. Special sample holder was used to observe current division and sharing in two parallel coated conductor tapes. The variation of the voltage applied to the module for short-circuit test was from 1.82 (V) to 12.7 (V). [ABSTRACT FROM AUTHOR]

We present the comparison between the performance of an inductive superconducting fault current limiter operating with bulk Bi1.6Pb0.26Sr2Ca2Cu3O10+x rings or Y1Ba2 Cu3O7-δ thin-film washers as secondaries. We have measured the impedance offered by the limiter under current faults and the recovery time once the faults are cleared. Our results show that the use of thin films can improve the impedance response of these devices and especially their recovery time, which can be about two orders of magnitude shorter than that of bulk samples. [ABSTRACT FROM AUTHOR]

A resonance-type superconducting fault current limiter (FCL) using Bi-2223 superconducting coils was developed and tested in order to demonstrate its actual operation. Over-current tests of the FCL were carried out for 50 Hz steady-state current of up to 120 A with relevant combinations of a superconducting reactor, an arrester, a capacitance and a copper reactor. The test results showed that the currents during faults were controlled within low levels. It was also demonstrated that the FCL could promptly recover to the steady state after the faults were cleared. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SCFCL5) are expected to improve reliability and stability of power systems. To introduce an SCFCL to power systems, the repetitive operation at the severe continuous faults is one of the important function. The recovery time of the proposed 3-phase FCL was confirmed experimentally to be sufficiently short for the repetitive operation. This paper shows the experimental results and discussion on the repetitive current limiting operation of the 3-phase SCFCL, which was demonstrated in a model power system. The test condition was that the fault line is open at the fault within 100 ms and is re-closed within 930 ms, but the fault is not cleared during the interval while the fault line is open. It was confirmed that the SCFCL started to limit the fault current immediate after the fault and recover to the stand-by mode during the interval, and limited the fault current again at the re-closure without any degradation of the trigger current level and the limiting impedance. [ABSTRACT FROM AUTHOR]