A novel energy efficient SFCL with a silver-free contact switchgear for application in electricity and transportation

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-T_c superconducting active elements, in the form of layered flat rings of a Bi_1.8Pb_0.3Sr_1.9Ca₂Cu₃O_x 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.