A YBCO-coated conductor for a fault current limiter: architecture influences and optical study

YBaCuO-coated conductors (CC) are particularly interesting for the electric grid, especially for superconducting (SC) fault current limiters (FCL). This innovative device should play an important part in the future electric energy landscape. New network diagrams are indeed imagined with DC buses. The SC FCL would solve the delicate problem of DC fault currents. We have studied several YBaCuO-coated conductors with different architectures. A test bench for optical measurements has been developed to study the bubble development during limitation or over-current operation. The observations give useful information about the quench initiation and its propagation. The images were recorded every 0.2 ms (or less). Preliminary experiments have been carried out using a copper strip. Several operating temperatures have been investigated and important differences have been observed in some cases. The different YBaCuO CC studied show very different behaviours. Bubbles appear under the shape of strips across the tape or show a homogeneous behaviour. These behaviours are correlated by electrical measurements.