Development of a 7.5 MVA superconducting fault current limiter

Using a new design concept, a 7.5 MVA superconducting fault current limiter (SCFCL) is being developed. The basic principles of operation and its practical application has been successfully demonstrated using a 12 kVA experimental SCFCL. The current limiting effect has been achieved by the almost instantaneous increase in the device impedance due to the superconducting to resistive state transition of the HTSC material, triggered by combined effect of magnetic field and fault current in excess of the critical levels. The design concept is hybrid (inductive/resistive) with the SC elements placed inside a low inductance winding, which is used to generate an external magnetic field for uniform quenching and first response. A composite reaction textured Bi-2212 has been modified to optimise its electrical, mechanical and thermal properties, specifically for use in a SCFCL. Experience gained during manufacturing and testing of the SCFCL and its technical and economical implications of a typical SCFCL at a distribution system level are summarized in this paper. The way forward, future considerations and applicability of the results for the development of future superconducting power systems components are summarized in the concluding part of the paper.