200 kA DC Busbar Demonstrator DEMO 200 – Conceptual Design of Superconducting 20 kA Busbar Modules Made of HTS CroCo Strands

The High Temperature Superconductor (HTS) material REBCO provides high critical currents even when being cooled with liquid nitrogen (LN ₂ ) to T ∼ 70–77 K. Therefore, it is considered in the design of energy-efficient superconducting busbar solutions for industrial high-current application such as electrolysis. The research project DEMO 200 aims to demonstrate a modular, superconducting, LN ₂ –cooled 200 kA DC busbar for an aluminum electrolysis plant. Within that project, the electromagnetic design and analysis of a round arrangement of twelve individual compact HTS CrossConductor (HTS CroCo) strands is carried out. The HTS CroCo strands are fabricated from REBCO tapes of 2 mm and 3 mm width. For the electromagnetic design of the modules and busbar, the angular field dependence of the critical current of the REBCO material was characterized at relevant temperature and field ranges. The data is used as an input for an electromagnetic model to determine the required amount of REBCO to achieve the target critical current in the modular 200 kA busbar. For a sub-scale test of one module at T = 77 K, the expected critical currents are calculated to allow for the assessment of measured critical currents. In order to compensate the thermal expansion during cooldown to operational temperature, a concept based on the reduction of the amplitude of sinusoidal arrangement of HTS CroCo strands along a cylinder barrel is proposed and investigated with respect to its electromechanical boundaries.