Reduction of inductance and current rating of the coil and enhancement of fault current limiting capability of a rectifier type superconducting faultcurrent limiter

A rectifier type superconducting fault current limiter is mainly composed o f a rectifier using diodes and/or thyristors, and a superconducting coil. I t has advantages in tile following aspects. It can control the fault curren t level by controlling the coil current. Ac losses can be reduced because t he current through the super conducting coil is rectified de current. But t he longer the fault current limiting time is, the larger the superconductin g coil current becomes and the fault current level increases due to the inc rease of the coil current. This paper shows how to reduce the inductance an d current rating of the coil and how to increase the fault current limiting capability. The idea is to put a resistor in series with the superconducti ng coil for absorbing the incoming energy into the coil and turn on and off the switching device connected in parallel with the resistor in order to c ontrol the coil current in a pre-set region. Simulation results assuming th e fault current limiter as an inter-connecting device between a generator o f IPP (Independent Power Producers) and utility grids, and some experimenta l results with a laboratory model will be shown.