Numerical investigations of ReBCO conductors

with high limitation electric field for HVDC SFCL

Superconducting fault current limiters (SFCL) are already in operation in alternative current medium voltage applications and their use in HVDC grids is very promising due to their capability of reducing high short-circuit currents. In the European project FASTGRID, started in January 2017, a 50-kV DC SFCL demonstrator will be built and tested. This limiter is expected to be made with state-of-the-art ReBCO conductors with a critical current of 1000 A/cm (at 65 K, self-field) and a limitation electric field of 150 V/m. To investigate the architecture of the conductor, a numerical model has been developed and confronted to experimental results. To increase the normal resistance of the conductor, various steps have been investigated such as the alloying of the silver layer and the addition of a highly resistive shunt. Two bonding techniques (solder or glue) have been considered to assemble the shunt on the conductor. This paper compares theoretical results of different architectures of conductors to be tested in small SFCL pancakes.

Keywords — epoxy composites; hexagonal boron nitride; AC breakdown strength; DC conductivity; electrical conduction mechanisms.