The increased use of distributed power generation has led to increasingly high fault current
levels. A superconducting fault current limiter (SFCL) is a potential solution to prevent the
problem of short-circuit currents. YBCO-coated conductors (CCs) are one of the most
promising superconducting materials for SFCLs. Most YBCO CCs have stabilizers, which
play a significant role in limiting the fault current in the SFCL. Therefore, the selection of
the appropriate material and the thickness of the stabilizer of the CC used for the SFCL
may affect its quench/recovery characteristics. In this paper, the quench/recovery
characteristics of YBCO CC tapes having stabilizers with various thicknesses were
investigated. The quench/recovery test results showed that, as the thickness of the
stabilizer decreased, both the final approach temperature and the recovery time decreased.
This paper presents the effects of thermal grease on the electrical and thermal characteristics of GdBCO pancake coils, observed through charge-discharge, sudden discharge, over-current, and thermal quench testing. In charge-discharge and sudden discharge tests, a coil using thermal grease as an insulation material demonstrated faster charging/discharging rates compared to a coil without turn-to-turn insulation. In the case of over-current tests, the coil using thermal grease exhibited the highest electrical stability. Furthermore, thermal quench testing showed the coil employing thermal grease to possess superior thermal characteristics, with rapid cooling and low temperature rise. Overall, the use of thermal grease as an insulation material may be a potential solution to the problems observed with the existing insulation materials, possessing fast charging/discharging rates with superior thermal and electrical stabilities.
This study examined the effects of external pressures on the thermal and electrical stabilities of stacked GdBCO CCs through quench tests. The minimum quench energies and two-dimensional normal zone propagation velocities of stacked GdBCO CCs connected electrically in series under various external pressures were examined. The quench test results showed that the minimum quench energy increased with increasing the external pressure. Longitudinal normal zone propagation velocities were greater than transverse normal zone propagation velocities. Moreover, normal zone propagation velocities increased with increasing applied pressure implying that applied pressure resulted in increased layer-to-layer thermal contact that allowed hot spots to dissipate more easily.Index Terms-GdBCO CC, minimum quench energy (MQE), normal zone propagation (NZP), thermal/electrical stability.
Herein, we report a feasibility study for elimination of the screening current-induced field (SCIF) in fully insulated (INS) and no-insulation (NI) GdBCO coated conductor (CC) coils exposed to an external AC magnetic field generated by background solenoid copper coils. Prior to investigating the effects of external AC magnetic fields on SCIF in the GdBCO CC coils, the magnetic flux density (B z ) was calculated using the equivalent circuit model and compared to the B z obtained empirically to quantify the SCIF in the INS and NI coils. The value of the SCIF in the NI coil was smaller than that in the INS coil without the use of an external AC magnetic field, due to the current paths originating from the turn-to-turn and layer-to-layer contacts, suggesting that the screening current dissipated by contact resistance during charging. When the INS and NI coils were exposed to the external AC magnetic field, the B z of the coils increased gradually, and eventually saturating to the calculated B z values, indicating full removal of the SCIF. In addition, the SCIF of the NI coil could be removed under subjection to a lower external AC magnetic field compared to the INS coil, due to the lower SCIF occurring in the NI coil after charging.
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