The application of superconducting fault current limiters (SCFCLs) in power systems is very attractive because SCFCLs offer superior technical performance in comparison to conventional devices to limit fault currents. Negligible impedance at normal conditions, fast and effective current limitation within the first current rise and repetitive operation with fast and automatic recovery are the main attributes for SCFCLs. In recent years there has been a significant progress in the research and development (R&D) of SCFCLs. This paper gives an extended review of different SCFCL concepts, SCFCL applications and the R&D status. Within the first part of this paper the most important SCFCLS and, to a limited extent, non-superconducting fault current limiter (FCL) concepts are explained and compared. The second part reviews interesting SCFCL applications at the distribution and transmission voltage level and the third part shows in detail the R&D status. It can be summarized that SCFCLs are, at present, not commercially available but several successful field tests demonstrated the technical feasibility of SCFCLs. First distribution level applications are expected soon. Considerable economical and technical benefits can be achieved by applying SCFCLs at the distribution and transmission voltage level.

https://iopscience.iop.org/article/10.1088/0953-2048/20/3/R01/pdf

High-temperature superconductor fault current limiters: concepts, applications, and development status

Power systems are becoming more and more complex in nature due to the integration of several power electronic devices. Protection of such systems and augmentation of reliability as well as stability highly depend on limiting the fault currents. Several fault current limiters (FCLs) have been applied in power systems as they provide rapid and efficient fault current limitation. This paper presents a comprehensive literature review of the application of different types of FCLs in power systems. Applications of superconducting and non-superconducting FCLs are categorized as: (1) application in generation, transmission and distribution networks; (2) application in alternating current (AC)/direct current (DC) systems; (3) application in renewable energy resources integration; (4) application in distributed generation (DG); and (5) application for reliability, stability and fault ride through capability enhancement. Modeling, impact and control strategies of several FCLs in power systems are presented with practical implementation cases in different countries. Recommendations are provided to improve the performance of the FCLs in power systems with modification of its structures, optimal placement and proper control design. This review paper will be a good foundation for researchers working in power system stability issues and for industry to implement the ongoing research advancement in real systems.

https://www.mdpi.com/1996-1073/11/5/1025/pdf

Fault Current Limiters in Power Systems: A Comprehensive Review

The flux-lock type high-Tc superconducting fault current limiter (SFCL) has different fault current limiting characteristics according to the winding direction between coil 1 and coil 2. In this paper, the fault current limiting characteristics and the resistance of high-Tc superconducting (HTSC) element in the flux-lock type SFCL without the 3rd winding due to the winding direction were analyzed based on the equivalent circuit with the magnetization branch. In addition, we investigated the fault current limiting characteristics of it along the number of turns of coil 2 with the fixed number of turns of coil 1 through the fault current limiting experiments. In case that coil 1 was wound to the same winding direction as coil 2, or, subtractive polarity winding, the more the number of turns in coil 2 for the fixed turns of coil 1, the higher the resistance of HTSC element and the limited line current. On the other hand, the additive polarity winding case, which coil 1 was wound to the reverse winding direction of coil 2, showed the opposite operational characteristics to the case of the subtractive polarity winding. The experimental results for each winding direction were well coincided with the analyzed ones from the equivalent circuit.

Fault current limiting characteristics due to winding direction between coil 1 and coil 2 in a flux-lock type SFCL

Resistive fault current limiters which consist of a YBCO film and a normal conducting film were constructed. The YBCO film was connected by indium wires to the normal conducting film in parallel at intervals of about 10 mm to increase the allowed voltage across the fault current limiter during the current-limiting operation. Current limiting experiments show that an allowed voltage across the fault current limiter during current-limiting operation of over 13 V/cm was achieved. Moreover, by combining in parallel 2 sets of 3 serially connected fault current limiters fabricated using 100 mm/spl times/10 mm YBCO film, a rated power of over 20 kVA is obtained.

A new model of fault current limiter using YBCO thin film

Maximum short circuit current of a modern power system is becoming so large that the current should be reduced to make more efficient use of power system transmission capability. The fault current limiter (FCL) is a promising solution of this problem and it can be categorized into two types: constant impedance type FCL and current limiting type FCL. Current limiting type FCL such as rectifier type superconducting FCL (RSFCL) has variable equivalent impedance depending on the limit of the current through FCL and power system impedances. In this paper, a method is proposed to incorporate RSFCL into short circuit current analysis, which is needed to evaluate the effectiveness of FCL installed in a large scale power system. Also, an efficient method to find FCL locations suitable for reduction of short circuit currents of more than one fault location is developed. The efficiency and effectiveness of these methods are shown by numerical examples.

FCL location selection in large scale power system

Superconducting fault current limiters for electric power systems have been researched. A magnetic shielding type superconducting fault current limiter is developed in the authors' research on superconducting fault current limiters. This limiter consists of a copper primary winding, a superconducting cylinder, an iron core and a control coil. The superconducting cylinder has a Bi2212 thick film on a MgO substrate. The control coil consists of some metallic rings, and the fault level can be adjusted by changing the number of the rings. To design a prototype limiter, the AC magnetic shielding and loss characteristics of small models were measured. The prototype limiter is 6600 V in rated voltage and 400 A in rated current. The superconducting cylinder is 0.45 m in diameter and about 1 m in height. Only the superconducting cylinder was designed to be cooled by liquid nitrogen. The experimentally manufactured limiter is about 1.3 m in width, about 0.6 m in depth and about 2 m in height.

M. Ickikawa

Papers

Performance of a high-Tc superconducting fault current limiter-design of a 6.6 kV magnetic shielding type superconducting fault current limiter