Stacked Delta Design Of Three-Phase Permanent-Magnet Fault Current Limiters

This paper proposes an improvement for the dynamic performance of pre-saturated stacked permanent magnet biased three-phase fault current limiter (PMFCL) through COMSOL finite element simulation. The nonlinear demagnetization behaviour of the permanent magnet, especially in the upper part of the B-H curve with negative magnetic field intensity, has been modelled through the Jiles-Atherton method. This enables a realistic representation of the PMFCL dynamic behaviour throughout its entire operations of pre-fault, fault and fault removal, respectively. The experimental measurements were considered to validate the trends of the simulation outcomes during the entire operation of PMFCL. Extensive finite element simulation shows that the stacked design of PMFCL can increase the capability of fault current limiting with proper selection of the number and arrangement of the AC coils around the iron core (soft magnet). Results reveal that the division of AC coils into series differential connected sub coils, with an even number, can increase the limiting capability by increasing the AC coil number of turns, without exceeding the permissible tolerances of voltage drop and power losses. Moreover, this stacked design is subjected to parametric investigation for different fault types, either symmetrical or unsymmetrical, or even when changing the fault current peak value.