Recovery Characteristic Against Fault Current in Highly Homogeneous Coated Conductor

A Superconducting material for fault-current limiters is needed for various properties, such as equivalent resistance per length, maximum allowed electric field during fault, etc. The recovery characteristic is also an important property. In this paper, we report on the investigation of the recovery characteristic against the fault in our highly homogeneous rare-earth barium-copper oxide-coated conductors, which have been manufactured by Fujikura Ltd. The fault-current experiments to determine the recovery time of coated conductors were carried out through the procedure as follows: 1) applying the overcurrent for 60 ms (= 3 cycles); 2) interrupting current flow, then waiting for a certain breaking time; and 3) applying the normal operating current, which was set its peak value as about 50% of sample I
_c
for 200 ms (= 10 cycles). Experimental results show that the coated conductor needs a few seconds to recover its superconducting state after the fault current was removed. The recovery time varies depending on the rate of temperature increase during the fault. It suggests that the cooling effect of liquid nitrogen is affected by the largeness of the contact area between the surfaces of the coated conductor. The difference of the Ag layer thickness hardly affects recovery time due to its structure. The Ag layer thickness is sufficiently thin compared with the total thickness and width of the coated conductor.