Experimental Testing and Development of Improved Modelling for Multistrand Resistive SFCL

Magnesium diboride (MgB2) in a simple round wire form has been tested and shown to be suitable as a low-cost resistive superconducting fault current limiter (SFCL). The commercial exploitation of MgB2 SFCLs requires a considerable scale-up of the current-carrying capability of the MgB2 wire. A multistrand MgB2 wire was developed for an SFCL coil to increase the current capacity. This paper will briefly report on the experimental results on a three-strand MgB2 coil used as a resistive SFCL. An improved analytical model that predicts the behavior of the three-strand SFCL coil was developed, taking the temperature and critical current variation along the wire into consideration. Variations in the critical current along the wire are to be expected as a consequence of normal manufacturing tolerances. The predicted current using the improved analytical model showed good correlation with the experimental test results at different fault current levels. The improved analytical model is a useful tool for the practical design of commercial SFCLs.