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This study presents the development of a PSCAD/EMTDC analysis model for the 154 kV SFCL in South Korea, which will be applied to the Korean power system in 2015. The analysis model is developed by using the operating mechanism supported by the developer of the SFCL, KEPRI (Korea Electric Power Research Institute). And then this paper proposes some candidate locations and design specifications for the successful demonstration application of the 154 kV SFCL to Korean power systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model a hybrid SFCL which solves a late recovery time after quenching. [•] We examine the hybrid SFCL to the Dangjin multi-unit power plant in Korea. [•] The hybrid SFCL decreases the acceleration power of the generators during a fault. [•] Reducing tripped generators is verified that transient stability will be improved. [ABSTRACT FROM AUTHOR]

Highlights: [•] The equivalent circuit equations and the heat balance equations were established. [•] The current distributions of the HTS cable under fault current were obtained. [•] The temperature curves of conductor layers under fault current were obtained. [•] The effect of the gap liquid nitrogen on the thermal characteristics was studied. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the transformer type superconducting fault current limiter (SFCL) with two triggering current levels was suggested and its current limiting characteristics were analyzed. The structure of the suggested transformer type SFCL with two triggering current levels largely consists of two parts. One is the transformer with two magnetically coupled coils, which correspond to the primary winding and the secondary one connected with one high-T C superconducting (HTSC) element. The other is third coil, or, another secondary winding with one HTSC element, which is wound on the same iron core together with two coils. This suggested transformer type SFCL can limit the fault current by generating its limiting impedance with two different amplitudes, which are dependent on the initial amplitude of the fault current in case of the fault occurrence. To confirm the usefulness of the proposed SFCL, the current limiting tests of the SFCL according to the fault angle, one of the effective fault conditions to affect the amplitude of the initial fault current, were carried out and its effective limiting operations were discussed. [Copyright &y& Elsevier]

Abstract: We reported the fabrication and analysis of the reactor for matrix-type superconducting fault current limiters (SFCLs). Reactors take a role of inducting magnetic field to superconductors in reactors and bypassing partial fault currents to themselves. Superconductors used in this work were YBCO thin films deposited on 5.08cm diameter Al2O3 substrates. Also, reactors with a diameter of 90mm and a length of 230mm were fabricated. Then, we constructed the matrix-type SFCLs with a reactor which consists of a trigger part and current limiting parts. Experimental results are reported in terms of the characteristics of fault current in superconductors and reactors, and distribution of the fault power between them. [Copyright &y& Elsevier]

Abstract: The amount of consumed power is increasing with industrial development and rapidly increasing population. In accidents due to increased power consumption, the fault current sharply increases. Superconducting fault current limiters (SFCL) are studied widely to limit such fault currents. In this study, the characteristics of a transformer-type SFCL are analyzed depending on reclosing in changing the number of secondary winding turns. For experiment conditions, the turn ratio of the primary and secondary windings of a transformer-type SFCL was set to 4:2 and 4:4. The voltage was incremented by 80V from 120V for the experiment. The circuit breaker was operated with two open times of CO-0.17s –CO-0.17s –CO seconds (C; closed, O; open), respectively. Comparing the result for the experiment conditions with the case of the turn ratios of the primary and secondary windings at 4:4 and 4:2, the fault current was limited effectively in 4:2 than in 4:4 for the fault current limit ratios. With respect to the result of recovery characteristics, it was examined that the superconducting unit recovered faster when the turn ratio of the primary and secondary windings was 4:2 than 4:4. Comparing the amount of consumed power related to the recovery characteristics of the superconducting element, it was examined that the recovery time was faster in less power consumption for the superconducting unit. As such, since a transformer-type SFCL depending on reclosing in changing the number of turns of the secondary winding controls the turn ratio of the secondary winding to control fault current limiting and recovery characteristics, it can normally operate. [Copyright &y& Elsevier]

Abstract: In this paper we analyzed recovery characteristics of matrix-type SFCLs (MFCL) with 2×3 matrixes when triple lines-to-ground fault occurred. MFCLs used in this work consist of 18 superconductors, six reactors for induction of magnetic field and several parallel impedances for bypassing fault currents. Also we analyzed recovery characteristics of resistive-type SFCLs of which 18 superconductors are connected in series and parallel, without reactors and parallel impedances, for the purpose of comparison, under the same experimental conditions of MFCLs. Experimental results were reported in terms of recovery characteristics for individual superconductors in an R phase, dependency of faults cycles and applied fault voltages in each phase. We confirmed that recovery characteristics of MFCLs were more excellent than those of resistive-type SFCLs. [ABSTRACT FROM AUTHOR]

Abstract: The new Japanese national project of development of 66kV/5kA high-temperature superconducting (HTS) power cables has been started since 2008. In an AC power system, a fault current may flow in the event of a short circuit accident. The maximum fault current condition is defined to be 31.5kArms for duration of 2s for 66kV class transmission line in this project. Therefore, one of the technical targets in this project is to design the HTS power cable to survive at this fault current condition. The coated conductors have copper layer as a stabilizer not to be damaged by over-currents. The HTS cable has a copper former and copper shield layers in parallel with the HTS conductor layers and HTS shield layers, respectively, to control the temperature rises in the HTS cable at a fault accident. In this study, we simulated the maximum temperature rises in the HTS power cable at the fault current condition of 31.5kArms for 2s in order to design the copper stabilizer and copper shield layers by using a computer program we developed on the basis of 3D finite element method (FEM) and electrical circuit model. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the characteristic analysis of 154kV HTS power cable system under fault conditions using PSCAD/EMTDC (Power System Computer Aided Design/Electromagnetic Transients including DC). Before applying the HTS power cable to the real utility, the system needs to be analyzed using certain simulation tools. The resistance of conventional power cables is not changed by fault current. But HTS power cable has some different properties. The impedance of superconductor is dramatically changed along with the current over the critical value, temperature, and magnetic field. PSCAD/EMTDC does not provide the HTS power cable model which includes the same electrical characteristics of real HTS power cable. In order to develop the EMTDC model component of 154kV class HTS power cable, the authors have manufactured a 1/58 HTS model power cable and experimented under several types of fault conditions. The measured characteristics of the model cable, resistance and temperature variation, were used to develop the HTS power cable model component in EMTDC. Using this model component, HTS power cable system was analyzed under the fault conditions. The simulation results of fault current, temperature and resistance variation of HTS power cable are described in detail, and how to apply the characteristics of HTS power cable in the simulation tool is also discussed in order to demonstrate the effectiveness of the proposed model component of 154kV class HTS power cable. [Copyright &y& Elsevier]

Abstract: A new high temperature superconducting (HTS) cable project supported by Ministry of Economy, Trade and Industry (METI) and New Energy and Industrial Technology Development Organization (NEDO) has started in Japan. Target of this project is to demonstrate the reliable and stable operate of a 66kV, 200 MVA HTS cable in the grid. Tokyo Electric Power Company (TEPCO) provides the real grid and studies the impact of connecting the HTS cable to the existing conventional facilities in Yokohama. Sumitomo Electric Industries, Ltd. (SEI) manufactures the HTS cable, terminations and joint. Mayekawa Corporation provides a cooling system. One of the technical targets in the project is to reduce the AC loss of superconducting cable. For this purpose, a new type DI-BSCCO, which is a production name of BSCCO wires made by SEI, with twisted superconducting filaments is planed to be applied in the cable. A short cable core using the new wires shows less AC loss than 1W/m/ph at 2kArms. Another important point is to design a cable system to withstand a large over current at a short circuit failure. At a preliminary test with a short cable, it was recognized that the cable had no degradation of conductor Ic after applying the fault current of 31.5kA for 2s, which are required for 66kV line. This report shows details of these experiment results and design of the cable. [Copyright &y& Elsevier]

Abstract: In this paper we described the improved design for the matrix fault current limiters (MFCL). To do this, we used thin film-type superconducting elements. therefore it means that we can make the MFCL with minimized size and high switching speed because of the high current density and the high indexing value of superconducting thin film. Also we could minimize the bulky shunt coil using the connection of a series resistance with a shunt coil. Also we could effectively block up a leakage current in shunt coils under no-fault condition and simply control total impedances of a current-limiting part using this method. After we designed an appropriated 1×2 basic MFCL module with an applied voltage of 160V, we enlarged it to a 2×2 MFCL module and a 3×2 MFCL module where applied voltages were 320V and 480V, respectively. Experimental results for our MFCL were reported in terms of various fault currents, variation of series resistance and so on. We think that these methods will be useful in the optimum design of an m × n MFCL. [Copyright &y& Elsevier]

Abstract: This paper presents the operation principle of a new type active superconducting fault current limiter (SFCL). The SFCL is composed of an air-core superconducting transformer, a PWM converter and a superconducting magnet. The primary winding of the air-core superconducting transformer is in series with AC main circuit, and the second winding is connected with the superconducting magnet through a PWM converter. In normal (no fault) operating state, the flux in air core is compensated to zero, so the SFCL has no influence on main circuit. In the case of short circuit, by controlling the amplitude and phase angle of the second winding’s current, the limiting impedance which is in series with the AC main circuit can be regulated and the fault current will be limited to a certain level. Using MATLAB SIMULINK, the simplified model of the active SFCL is created, and simulations validate this SFCL can suppress the fault current effectively. In addition, the current-limiting experiment is done with a small conventional transformer. Experimental results correspond well with simulation results. [Copyright &y& Elsevier]

Abstract: With the extensive application of DC power systems, suppression of DC fault current is an important subject that guarantees system security. This paper presents an active superconducting DC fault current limiter (DC-SFCL) based on flux compensation. The DC-SFCL is composed of two superconducting windings wound on a single iron core, the primary winding is in series with DC power system, and the second winding is connected with AC power system through a PWM converter. In normal operating state, the flux in the iron core is compensated to zero, and the SFCL has no influence on DC power system. In the case of DC system accident, through regulating the active power exchange between the SFCL’s second winding and the AC power system, the current on the DC side can be limited to different level complying with the system demand. Moreover, the PWM converter that interface the DC system and AC system can be controlled as a reactive power source to supply voltage support for the AC side, which has little influence on the performance of SFCL. Using MATLAB SIMULINK, the mathematic model of the DC-SFCL is created, simulation results validate the dynamics of system, and the performance of DC-SFCL is confirmed. [Copyright &y& Elsevier]

We have been developing a superconducting fault current limiting transformer (SFCLT) with 3-phase, 500/275 kV, 625 MVA and optimized the main parameters by EMTP simulation. In this paper, we designed and fabricated an experimental scale-down model of SFCLT with 3-phase, 275/105 V, 6.25 kVA, using NbTi superconducting wire. We introduced the experimental model SFCLT into a transient network analyzer consisted of synchronous generators, transformers, transmission lines, circuit breakers and an infinite bus. It was revealed that experimental model had effective function-parameters as was simulated and experimental results clarified the effectiveness of SFCLT having both functions of the fault current suppression and the system stability improvement in a future superconducting power system. [Copyright &y& Elsevier]

• The numerical method is introduced to investigate the distribution of current density for the patterns that be used in R-SFCL fabrication. • In order to increase the superconductivity stability of the R-SFCL that results in the stability of the power systems, it is better to use modified patterns in the construction of the R-SFCL. • We proposed a pattern that its stability and uniformity is more than other modified patterns. The increase of current uniformity along of a Resistive type Superconductor Fault Current Limiter (R-SFCL) in the design of this type of limiters is well perceived as an important issue. The non-uniform distribution of current in R-SFCL only increases the current in some superconducting regions, as a result, in the fault conditions, only certain parts of the superconductor undergo a phase change that increases the heat pressure in those areas and causes the breakdown and destruction of the device. In this paper, the current density distributions in common patterns used in R-SFCs constructions have been simulated and investigated. To this end, an effective model is proposed for R-SFCL to achieve the highest uniformity of current and harmonic phase change over superconductors compared to other patterns. The simulation results in the Ansys Maxwell Software advocate the appropriate and satisfying performance of the proposed model. [ABSTRACT FROM AUTHOR]

• Transient stability enhancement in two-area multi-machine system at uncertainties. • FACTS devices such as DPFC and UPFC are used to enhance the transient stability. • Resistive SFCL is suggested for mitigating the fault currents at diverse faults. • Compared the performance of DPFC and SFCL with UPFC and SFCL at uncertainties. This paper presents a novel approach in two-area interconnected power system for enriching the transient stability at perturbations. The challenging task in the interconnected system is to equalize the power production and load demand without changing the system parameters. Therefore, a sophisticated controller of flexible alternating current transmission system (FACTS) called distributed power flow controller (DPFC) is suggested to the two-area power system for enhancing the system stability. Furthermore, the resistive type superconducting fault current limiter (SFCL) is also suggested to employ with DPFC for alleviating the fault current, and power quality issues. In this work, three cases are investigated by using without auxiliary, SFCL, unified power flow controller (UPFC), SFCL-UPFC, and SFCL-DPFC on two-area multi-machine system. The objectives of the paper are to determine and evaluate the fault current, variations in voltage and inter-area oscillations, ascertain the performance of suggested techniques at diverse fault-clearance times, and find out the finest control method for different kinds of faults. The simulation outcomes disclose that the coordination of SFCL and DPFC yielded finer outcomes over other control approaches. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the performance of a prototype resistive fault current limiter (FCL) made using a high temperature superconductor (HTS). Its behavior under normal operation and short-circuit conditions in a 6kV/1kA power system is analyzed with regard to the feasibility of using this HTS FCL device in electrical power systems. [Copyright &y& Elsevier]