Abstract
A promising solution of the fault current problem in power systems is the application of fast-operating nonlinear superconducting fault current limiters (SFCLs) with the capability of rapidly increasing their impedance, and thus limiting high fault currents. We report the results of experiments with models of inductive (transformer type) SFCLs based on the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa). It was shown that the SFCLs meet the main requirements to fault current limiters: they possess low impedance in the nominal regime of the protected circuit and can fast increase their impedance limiting both the transient and the steady-state fault currents. The study of quenching currents of MgB2 rings (SFCL activation current) and AC losses in the rings shows that the quenching current density and critical current density determined from AC losses can be 10-20 times less than the critical current determined from the magnetization experiments.
Highlights
We report the results of experiments with models of inductive superconducting fault current limiters (SFCLs) based on the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa)
The study of quenching currents of MgB2 rings (SFCL activation current) and AC losses in the rings shows that the quenching current density and critical current density determined from AC losses can be 10-20 times less than the critical current determined from the magnetization experiments
One of the promising solutions of the fault current problem in power systems is the application of fast-operating nonlinear current limiters (FCLs) with the capability of rapidly increasing their impedance, and limiting high fault currents
Summary
One of the promising solutions of the fault current problem in power systems is the application of fast-operating nonlinear current limiters (FCLs) with the capability of rapidly increasing their impedance, and limiting high fault currents. Devices based on the superconductor magnesium diboride MgB2 with critical temperature Tc = 39 K can operate at temperatures of liquid helium, hydrogen or even neon This compound can be envisaged for many applications, as fault current limiters, MRI magnets, cables, electromotors, magnetic bearings, etc [2,5,6,7]. In the present paper we estimate applicability of the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa) in inductive (transformer type) SFCLs. Using an inductive SFCL model AC losses and the current causing transition into the resistive state (the quenching current Iq) were measured. The used contactless method suitable for samples in the form of a closed loop (hollow cylinder, ring, or short-circuited coil) is based on using the transformer configuration (Figure 1) [7]. The critical temperature of the MgB2 samples was estimated to be about 37 K
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