Testing of an Inductive Current-Limiting Device Based on High-T-c Superconductors

An inductive current-limiting device based on transition of a superconductor to the normal state is investigated. The device has low impedance under normal conditions of the circuit to be protected, and a high impedance developed rapidly in a self-switching mode under fault conditions. A model. of the device consisting of a copper coil and a high-temperature superconducting ring, coupled magnetically, was tested. It is shown that the transition of the ring to the normal state and its return to the superconducting state take place in a relatively smooth manner, and does not lead to overvoltages across circuit elements. On the other hand, the rate of impedance rise is sufficient to limit both the steady-state and transient components of fault current. The influence of thermal processes in the ring on transient responses in the circuit with the CLD is discussed. Some considerations for a full size design are also presented.