Compact designs of permanent-magnet biased fault current limiters

This study proposes two novel compact designs of three-phase permanent-magnet biased fault current limiters (PMFCLs), namely, delta-shaped and compact cross delta PMFCLs. The actual representation of neodymium permanent magnet (PM) is based on the Jiles-Atherton modelling for the demagnetisation behaviour in the second quadrant of its actual non-linear B-H hysteresis loop. This PM is a preliminary representation validated through experimental measurements to ensure the trends and behaviour of PMFCL during its entire pre-fault, fault and post-fault recovery durations. Comprehensive time-domain, electromagnetic finite-element simulations, through COMSOL multiphysics package, have been conducted to study the relative effect of the constructive controlling parameters on the general performance of these proposed PMFCLs. However, the general performance of PMFCL can be characterised through the voltage drop and power losses of normal operation, and the fault current clipping ratio during the fault condition. Results reveal that the compact cross delta design has superior performance and enhanced capability of limiting any type of fault current, either symmetrical or unsymmetrical, with leading advantages of significant reduction of the voltage drop across PMFCL and power losses during the normal operation of the grid.