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A novel concept of a switchgear based on the combination of an AC superconducting fault current limiter (SFCL) and silver-free electrical contacts is proposed. In the combined system SFCL+switchgear, it is possible to employ cheaper materials for electrical contacts. The SFCL device includes inductive coupling of high-Tc superconducting active elements, in the form of layered flat rings of a Bi1.8Pb0.3Sr1.9Ca2Cu3Ox compound, prepared by a solid-state reaction technique. Experimental results obtained by testing a prototype SFCL in short circuit regime at AC 50 Hz under quasistationary conditions are presented. The use of the superconducting rings enables a wide range variation of the dissipated power. Copper/diamond composites, prepared by explosive synthesis, are employed as contact materials for the switchgear. The addition of particles (<1 μm) leads to improved mechanical characteristics and increased stability of the composite materials. The combination of switchgear with silver-free electrical contacts and SFCL allows a short circuit regime to withstand the switchgear and provides increased system reliability.
Date of Publication: Jun 2002