Fault Current Limiters (FCLs) are proposed widely in literature for improving different characteristics of electric power system. Solving protection problems in smart distribution networks in presence of distributed generation (DG) is an example for the applications of FCLs discussed in recent papers. Voltage sag during Faults is a power quality (PQ) concern in the power system. In this paper, it is shown that in smart distribution networks including microgrids, FCL can effectively alleviate this problem, according to the Fault location. Therefore, a bidirectional non-Superconducting Fault Current Limiter (BNSFCL) is presented in this research, so that the bidirectional Fault suppression has become available. Analytical analysis and simulations are provided to validate the effectiveness of the BNSFCL topology. Results show that by using proposed structure in distribution networks with microgrids, both protection and PQ status are enhanced, i. e. the BNSFCL prevents deep voltage sag and protection mis-coordination. The proposed topology can be applied in smart grid architecture _where the bidirectional Current flow has made conventional protection schemes useless_ effectively and can have acceptance for implementation as one of the future power system components.

Development of the electric networks led to more interconnection in this system, therefore high level of short circuit Faults flows in the networks. Many destructive damages such as instability, insulation problems and voltage mitigation can highly play unwanted influences on the system’s equipment. Using appropriate protection devices like high voltage fuses, fast switches, and such devices reduce these destructive effects. Superconducting Fault Currents Limiter (SFCL) as one of developing method of Fault Current reduction is able to be used for the mentioned goal. In this paper SFCL is studied in an AC electric railway system.

Voltage drop during the Fault can be effected on the performance of generation units such as wind turbines. The ability to ride through the Fault is important for these generation units. Superconducting Fault Current Limiter and Superconducting magnetic energy storage can improve the Fault ride through due to Fault Current limiting and voltage restoring ability during the Fault, respectively. This paper presents a method for optimal allocation and control of Superconducting magnetic energy storage and Superconducting Fault Current Limiters in meshed microgrids. For this purpose, the doubly-fed induction generator voltage deviation, the point of common coupling power deviation, the Fault Current of transmission lines, and Superconducting Fault Current Limiter and Superconducting magnetic energy storage characteristics were considered as objective functions. In this paper, the optimization is performed in single-step and two-step by particle swarm optimization algorithm, and the system with the optimal Superconducting magnetic energy storage and Superconducting Fault Current Limiters are analyzed and compared. The results of simulations show Superconducting Fault Current Limiter and Superconducting magnetic energy storage reduce 85% of voltage drop, decreases 63% of doubly fed induction generator power deviation, and limits the maximum Fault Current of transmission lines by 9.8 pu. Finally, the status of the studied system variables has been investigated, in two scenarios related to the different Fault locations with equipment that the optimal allocated.

In this paper, the impacts of installing Superconducting Fault Current Limiter (SFCL) in radial and loop power distribution system are evaluated to improve voltage sag in both cases of with and without distributed generations (DG). Among various SFCLs, the hybrid type with a Superconducting element in parallel with a Current limiting reactor (CLR) is selected. This is more effective than resistor-type SFCLs because it reduces the burden on the Superconducting element, ac losses and cost in distribution system. According to SFCLs impedance and their locations in power system, voltage sag will be improved by reducing the Fault Current. In this paper, SFCLs with various arrangement and CLR magnitudes are installed in distribution system and improving the voltage sags on different buses are examined according to Fault position. Area of severity (AOS) method and expected annual sag frequency (ESF) are used to analyze the voltage sag. The results show that installing SFCL can improve the voltage sags as well as Fault Current reduction in radial and loop distribution systems.

Doubly-fed induction generators (DFIGs) are crucial in wind turbines due to their advanced control features and efficient power conversion, but they're vulnerable to grid issues like voltage dips and short circuits. This study explores enhancing DFIGs' low voltage ride-through (LVRT) capabilities using a Superconducting Fault Current Limiter (SFCL) system. The SFCL's Superconducting coil plays a key role by limiting Fault Current to stabilize power output, reducing excessive Currents during Faults, and mitigating voltage fluctuations, protecting the rotor-side converter and gearbox. The research focuses on optimizing the coil's inductance to improve SFCL performance, showing through MATLAB/Simulink simulations that adjusting inductance can lessen rotor Current oscillations during short circuits. The results indicate significant enhancements in LVRT capabilities, reducing electrical and mechanical stress on generators and converters, preventing severe voltage drops, and maintaining torque levels. Incorporating an SFCL into DFIG systems greatly increases stability, reliability, and Fault tolerance, supporting more wind energy integration.

Active Superconducting Fault Current Limiter (ASFCL) is a new type of FCLs which can limit the Fault Current at different levels. It also has a particular ability to compensate for voltage series in the electrical power systems. In this paper, an optimal coordination method is proposed to calculate both optimal setting parameters of overCurrent relays (OCRs) and limiting the impedance of ASFCL. The optimal parameters of OCRs are obtained using the maximum pickup Current and minimum trip time method. In the next step, by applying a new DG unit to the microgrid, the optimal limiting impedance of ASFCL is obtained so that all OCRs could be coordinated without changing the relay setting parameters. Using MATLAB software, a typical distribution system connected to a microgrid with ASFCL is simulated and the simulation results are evaluated in terms of the Fault Current limitation and OCRs coordination. Simulation results confirm the appropriate performance of the proposed ASFCL for the above-mentioned purposes.

Power system protection at transmission and distribution levels based on overCurrent relays is essential based on their properties such as detection, stability, high speed, backup and error correction accuracy. Since distributed generation sources are connected to the power grid, they not only increase the short circuit level of the grid, but also disrupt the set point of main and backup relays, which will interrupt the healthy areas of the grid. In order to maintain the safety and stability of the network and to avoid increasing the power rating of the existing equipment, Superconducting Fault Current Limiter (SFCL) devices are utilized to significantly reduce the short circuit Current at its primary cycles. However using of SFCLs, may lead to inadequate relay performance and lack of short circuit Current detection. In order to solve the above problems, this paper presents a SFCL model with resistive structure and coupling inductance, while increasing the Fault impedance path and reducing short circuit Current, optimally. Then shielding synchronization between main relays and their near and far back-ups are achieved. Finally proposed objective function is minimized using the improved particle swarm optimization algorithm and three case studies will be performed. The simulation results represent the superiority of the proposed method in resolving the error and eliminating disturbance between the relays at the shortest possible time.

In this paper a new structure for Fault Current Limiter is proposed. In proposed structure the superconductor coil is replaced by a copper coil and the losses of copper coil and power electronic devices are compensated by an auxiliary circuit. The results show that the proposed structure has less undesired effect on normal operation of system compared with ordinary superconductor type.  The main advantageous of proposed structure are no need to superconductor technology and its control-less operation. The analytical analysis and designing characteristics for DC reactor are presented. Also, the simulation and experimental results are presented to show the effectiveness of proposed structure in Fault Current limitation.

In the event of voltage sag at the nearing of a wind park, severe Currents may pass through the power electronic devices of the Doubly Fed Induction Generators (DFIGs). Hence, according to the Low Voltage Ride Through (LVRT) requirements, the wind parks are allowed to disconnect from the network after a certain time. Therefore, to avoid such actions, the LVRT requirement of wind parks is considered to be enhanced in this paper. This aim is achieved by offering a novel objective function in order to find the optimum impedance of Superconducting Fault Current Limiter (SFCL). To evaluate the effectiveness of the proposed method, it is verified in MATLAB/SIMULINK and its great performance to amend the LVRT of such wind parks is corroborated by the simulation results.