Development of kA Class Fault Current Limiting Unit with YBCO Thin Films

Abstract

A kA-class fault current limiting unit (FCL unit) with YBCO thin films has been developed. The size of the YBCO film on a sapphire substrate with a metal shunt layer is 3cm in width and 10cm in length. The kA class unit consists of eight films in parallel. A polygonal arrangement of the YBCO films selected to keep the current distribution uniform. Moreover, the return pass of the current is set at the center axis of the unit. The model, connected to two units in series, was tested for normal operation and current limitation. The model carried 1kA for 1hour and 1.2kA for 5min without quench at normal operation, and the current distribution between the films was uniform. The short circuit tests were performed against a power line that has a prospective fault current of 8.9kA. A total of eight tests were successfully carried out at 200V, 3.5 cycles, and the model limited the fault current to 1.2kA.