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In this paper, we theoretically compared the fundamental characteristics of fault current limiter (FCL) with high-Tc superconductor (HTS) and two coaxial air-core coils based on steady-state analysis. Two types of FCL are possible. One is parallel type and the other is transformer type. The parallel type can be divided into two types according to the combination of the winding direction of coils. That is, there are two cases that the coils are wound so that the magnetic fluxes induced by coils reduce and increase each other. In this paper, we called them parallel type 1 and 2, respectively. There is no significant difference in the HTS volume required to satisfy both the specified limiting impedance ZFCL and initial current Iini in limiting operation among those three FCLs although the HTS in each type of FCL has different length and cross-sectional area. In the cases of those FCLs, we can improve the current limiting performance by arranging the HTS in the coils and applying the magnetic flux to the HTS in the limiting operation. The magnitudes of the magnetic flux density are almost the same. From the viewpoint of the FCL impedance in normal operation, parallel type 1 has the most desirable structure. On the other hand, transformer type is the best to eliminate the magnetic flux applied to the HTS in the normal operation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 29–36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20477

In this paper, it was assumed that a synchronous generator in a customer system was connected to a distribution system via the fault current limiter (FCL). We theoretically investigated the influence of the output power of the generator on the limiting effect of the fault current when a three-phase short-circuit fault occurs. It was shown that the fault current out of the customer system, limited by the FCL, rises with the output power of the generator. It was found that the larger the output, the higher the fault current at the fault point is when the limiting resistance is less than 15 Ω in the case of the resistive-type FCL. On the other hand, the fault current at the fault point decreases with an increase in the output power for a limiting resistance more than 15 Ω. In contrast, it was found that the suppressing effect on the fault current at the fault point due to the inductive-type FCL hardly depends on the output power. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 15–24, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10357

As equipment to limit the fault current in electric power systems, the superconducting fault current limiter (SC-FCL) is expected to be introduced. Since the SC-FCL was required to recover to the superconducting state rapidly after current interruption, it is important to understand the recovery characteristics of SC-FCL. In this paper, the recovery characteristics of SC-FCL in a 6.6-kV distribution system were theoretically investigated. We computed the time variation of superconducting cable temperature after quench and the recovery time for the commutation-type SC-FCL having the superconducting element connected to a limiting resistor in parallel. The calculations were carried out for different conditions of system impedance, limiting impedance of SC-FCL, and length of superconducting cable, considering the time–current characteristics of the protective relay. As a result, it is found that the recovery time decreases with an increase in system impedance and with a reduction in limiting impedance of SC-FCL. Furthermore, the decrease in length of superconducting cable causes the increase in the recovery time. © 2001 Scripta Technica, Electr Eng Jpn, 136(4): 26–33, 2001

Superconducting technology is regarded as a breakthrough to future electric power transmission because of its highly densified and large transmission capability. This paper proposes a concept of the future power system composed of various superconducting apparatuses. A prototype model system called “PROMISE (PROspective power transmission Model system Integrated under Superconducting Environment)” is constructed to prove the realization of the above concept. PROMISE is composed of a superconducting transformer (60 Hz, 6/3 kV, 1000 kVA class), superconducting fault current limiter (6 kV, 200 A class), and superconducting power cable (5 m, 6 kV, 650 A class). This paper also shows that PROMISE realized the transmission of the electric power of 3.8 kV–460 kVA (50 Hz). This is the first achievement in the world. The voltage-current synthetic test verified that PROMISE can withstand ac voltage of 6 kV while carrying ac current of 170 A (60 Hz). The ac loss of superconducting cables, the heat leak of cryostat and the core loss of the superconducting transformer are measured to estimate the transmission loss of PROMISE. These fundamental performances of PROMISE may indicate the feasibility of the future introduction of superconducting technology for electric power systems.