Current limiter could keep grids in step with renewables

Unlike conventional current limiters and fuses, the superconducting ceramic devices designed by researchers at the Karlsruhe Institute of Technology (KIT) are not destroyed by surges and maintain power throughout.

The team first grew a one-micron-thick YBCO crystal (yttrium, barium, copper, oxygen) layer directly on a stainless-steel strip of a few millimetres in width.

When the device is cooled below 90K (-183°C) the material becomes superconductive. However, superconductivity collapses abruptly when the current in the conductor exceeds predetermined design limits.

In the case of current peaks in the grid, the superconductor loses its conductivity within fractions of a second and the current then flows through the stainless-steel strip only, which has a much higher resistance and, thus, limits the current. The resultant heat is removed by the cooling system of the superconductor. A few seconds after the short circuit, it is returned to normal operation in the superconducting state.

‘The standard solution in the grid is a kind of fuse that burns through and has to be replaced by a service… you have to manage the power connection, repair everything or feed the current around other lines,’ project lead Dr Wilfried Goldacker told The Engineer.