Characterization of the Superconducting to Normal Transition of HTS Coated Conductors by Fast Pulsed Current Measurements

In this paper, we present measurements of the superconducting to normal transition (extended V-I curves) of commercial coated conductors with and without stabilizing copper layer. These measurements were realized with a custom developed pulsed current measurement (PCM) system. Currents between 5 to 10 times the critical current of commercial wires (up to 1000 A) can be applied for a period as short as 50-80 mus, limiting the energy released in the sample to a fraction of a Joule. For such short pulses, the temperature rise in the sample is relatively small, which allows characterizing the electrical resistivity of high temperature superconductors (HTS) at high current densities and electric fields. The data obtained will be used to develop more accurate models of HTS in the over-critical current regime, which is major issue for allowing the development of quality simulation tools for optimizing the design of superconducting fault current limiters. The PCM technique is also a very powerful tool for investigating the transient thermal behavior of coated conductors, whose better understanding is required in order to devise reliable fault current limiters based on this technology. So far, the measurements have been restricted to 77 K and self-field, but further works will extend the range of measurements to higher fields and temperatures.