AC Losses and Material Degradation Effects in a Superconducting Tape for SMES Applications

Superconducting Magnetic Energy Storage (SMES) systems are one potential application of superconductivity in electric grids. The main element of such systems is a coil, made from superconducting tape. Although SMES systems work in DC conditions, due to highly dynamic working regimes required for some applications, AC currents can appear in the coil. It is then of utmost importance to verify the magnitude of these AC currents and take into account AC losses generated on the tape in the design phase of such system. To assure a proper operation, it is also necessary to know tape characteristics during the device lifetime, which in normal operation conditions can be of decades. Continuous thermal cycles and mechanical stresses to which the tape is subjected can change its characteristics, changing important quantities like critical current (IC) and n-value. It is then also necessary to evaluate tape degradation due to these conditions. A study of AC losses will be here presented, for a short sample of BSCCO tape. IC and n-value degradation due to consecutive thermal cycles will also be studied.