Application Of Superconducting Fault Current Limiter Research Articles

Conceptual Design of a 110 kV Resistive Superconducting Fault Current Limiter Using MCP-BSCCO 2212 Bulk Material

Superconducting fault current limiters (SCFCLs) are new and attractive devices to limit short-circuit currents in power systems. In recent years, the technical feasibility of SCFCLs in medium voltage applications was successfully demonstrated in several field tests. In high voltage power systems the application of SCFCLs is very attractive too, because at this voltage level conventional devices to limit short-circuit currents are hardly applicable and system studies showed considerable economical benefits. Therefore, a German project started recently to develop a first 110 kV, 1.8 kA prototype of a resistive SCFCL. A magnetic triggered resistive concept using MCP-BSCCO 2212 bulk material will be used for the demonstrator. This paper reports about the conceptual design of this SCFCL and the project status. Focus is given on the main data of the 110 kV prototype, the SCFCL modules, the general design of the whole system and the most important high voltage design aspects. The calculations and estimations show that the conceptual design presented in this paper seems feasible and that a major technical challenge is to ensure a reliable electrical insulation system.

Transport properties of kA class QMG current limiting elements

In order to estimate the feasibility of a resistive type fault current limiter made of QMG, transport properties of QMG current limiting elements which can transport about 1 kA continuously in a superconducting state were studied. QMG is a rare earth based bulk superconductor that has high J c properties and relatively high electrical resistivity in a normal state. Because of these properties, QMG is a promising bulk material for superconducting fault current limiter applications. A bar-shaped sample in which the cross-section and the effective length were 2.2×0.8 mm 2 and 30 mm, respectively, was prepared. Bypass resistance of 7 mΩ was connected in parallel with the sample. A field assist mechanism that can apply a magnetic field of about 0.9 T to the sample was installed. A half cycle of AC current up to about 3 kA was applied to the samples at 77 K. In the case when applied current ( I) was less than 1000 A in a self-field, flux flow voltage was less than 0.5 mV. The n-value was about 6. In the applied field of 0.9 T, a rapid increase of voltage (quench) was observed around I=1820 A. The quench phenomena reproduced without degradation in the case of I>1820 A. From these results, it was found that QMG fault current elements can endure the thermal shock of the quench by the optimization of bypass resistance and the applied field.