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Copper-stabilized second generation high-temperature superconductor (HTS) coated conductors were modified to enhance their normal zone propagation velocity (NZPV). Experimental results, supported by numerical simulations, indicate that adding copper on the substrate side instead of adding it on the HTS side increases the NZPV by a factor of 2–3. Furthermore, a novel tape architecture, called hybrid-current flow diverter (CFD), was investigated. This hybrid-CFD tape was designed with the goal of having a very long current transfer length, which is the key to enhance the NZPV. Results show that it is possible to fabricate an HTS tape with double stabilizer thickness in comparison to a bare tape, while accelerating the NZPV by a factor of three. With the same approach, a ten-fold increase of the NZPV can be expected for a tape with a 40 µm thick copper-stabilizer.

The normal zone propagation velocity (NZPV) of three families of REBCO tape architectures designed for superconducting fault current limiters (SFCLs) and to be used in high voltage direct current (HVDC) transmission systems has been measured experimentally in liquid nitrogen at atmospheric pressure. The measured NZPVs span more than three orders of magnitude depending on the tape architectures. Numerical simulations based on finite elements allowed to reproduce well the experiments. The dynamic current transfer length (CTL) extracted from the numerical simulations was found to be the dominating characteristic length determining the NZPV instead of the thermal diffusion length. We therefore propose a simple analytical model, whose key parameters are the dynamic CTL, the heat capacity and the resistive losses in the metallic layers, to calculate the NZPV.

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