This article presents a comparison of inductive and resistive superconducting fault current limiter built with the same length of high temperature superconducting (HTS) tape. The resistive limiter is constructed as a noninductive bifilar winding. The inductive coreless limiter consists of primary winding and secondary shorted winding. Both limiters are connected parallel to the additional Cu primary winding, which helps to reduce the power dissipated in the HTS windings during and after a fault. It also ensures that in cases of an HTS tape failure, the protected circuit will not be disrupted. The limiters are very fast and the first peak is almost equally limited by both types of limiters.

In this work, we report on the design and tests results of a coreless inductive SFCL with a 600 A rated current for MV distribution system. The fault current limiter comprises of 4 identical units immersed in liquid nitrogen bath. Each unit consists of 3 windings. The primary and secondary windings made of 2G HTS tape SF12050 are magnetically coupled with the primary Cu winding. The high magnetic coupling between superconducting primary and secondary windings gives a low voltage drop on the limiter at nominal current. The presented solution reduces the size and the weight of the device. Tests performed at high power test facility prove the limiting capability of the coreless inductive SFCL.

The fault current limiting feature of the SC transformer with the HTS 2G windings provide protection and significantly reduce wear and tear for circuit breakers and other substation power equipment. A comparison of the short circuit currents of the 64 MVA transformer wound with copper and YBCO 2G HTS tapes is made in this paper. The results of the analysis show that the YBCO 2G tapes enable to built the superconducting transformer with the ability to limit the short-circuit currents. The superconducting windings require special considerations for the induced electromagnetic forces in order to limit them below the allowable tensile stresses. Strongly anisotropic Y-123 tape used in the winding of the transformer will be exposed to different orientations and amplitudes of the local magnetic field. If the transformer is going to act also as a fault current limiter, the uniformity of the transition of the transformer winding is crucial to avoid sectional responses of the transformer. Therefore it is essential to conduct systematic current-magnetic field measurements to define `constant current domain' for the conductor at a given operating temperature.

The superconducting fault current limiters (SFCLs) are highly effective solutions to reduce fault current in electric power system. The process of quenching may occur in all superconducting devices, but in fault current limiters this process must be fully controlled. Uncontrolled transition of the superconducting tape from the superconducting state to the resistive state may cause overheating and burning of the high temperature superconductor (HTS) tape and, consequently, lead to the destruction of the entire superconducting device. In this study, we described a simulation model to analyze the electrical and thermal behavior of the SFCL. By using this simulation model, we evaluated the transition of temperature of the REBCO coated conductor during the fault current limitation. We determined and described maximal parameters for the HTS tapes that can be applied to the superconductor without thermal degradation during fault.

Superconducting fault current limiters (SFCL) are designed to protect the electrical grid from faults that result from lightning strikes, downed power lines and other system interruptions. The rapid increase of impedance of the SFCL reduces the short current in the circuit. Several coreless constructions of inductive SFCLs have been tested. The space between the windings is the thick of the polyimide film kapton insulation to increase the coupling and reduces the leakage reactance. Both primary and secondary windings have been immersed in liquid nitrogen. The presented solutions reduce the size and the weight of the device. A few limiters based on HTS 1G and HTS 2G tapes has been described, tested and compared.

This paper presents the design and experimental results of a coreless superconducting fault current limiter (SFCL). The limiter has a rating of 15 kV and 140 A and was tested with a 2.5 GVA short-circuit generator. During the occurrence of a short circuit, the elements of the system are less exposed to electrodynamic and thermal overloads. The application of an SFCL leads to an increase of the capability of the power network for connecting distributed generation energy sources. Compact design of the coreless superconducting fault current limiter consists of three magnetically coupled windings cooled in liquid nitrogen. A high magnetic coupling between the superconducting windings gives a very low voltage on the limiter at a nominal current. The presented solution reduces size and weight of the device. The paper summarizes the design of the coreless limiter and presents in detail the results of tests performed at a high-power test facility.