Abstract
The application of a superconductor to a faultcurrent limiter in a power system has been researched.We developed a magnetic shielding type superconductingfault current limiter using a Bi2212 thick film cylinder.This limiter consists of a primary winding on asuperconducting cylinder for generating an AC magneticfield, the cylinder for shielding the field, an iron core formagnetic members and a control ring for controlling faultcurrents. When a fault occurs, the superconductivecylinder quenches and a magnetic circuit is formed insidethe cylinder. As a result, the limiter has a high impedanceto limit the fault current. The present study shows thelimiting and recovery characteristics of the fault currentlimiter.
I. INTRODUCTION
The recent growth of power circuit capacities has causedfault currents to increase. Since the protection of powersystems from the fault currents is very important, it isneeded to develop a fault current limiter. A fault currentlimiter is required to assure; (1) rapid reaction to faultcurrents, (2) low impedances in normal operation and (3)large impedances during fault conditions. A superconductingfault current limiter (SCFCL) can meet theserequirements. So far, various types of SCFCLs havebeen developed[ 11-[3]. The fundamental theory for thenew concept of SCFCL adopted in the present study wasproposed by several researchers[4]-[8]. The limiter uses asuperconductor to shield the magnetic field generated.The design is based on using a superconducive cylinderto shield the iron core from the AC magnetic fieldgenerated by the primary winding. During a fault caused,the magnetic field penetrates the superconducting shieldat a large impedance.In this work we examined the magnetic field shieldingof two oxide superconductive cylinders. We producedtwo magnetic shielding type SCFCLs with a control ring,and observed operating behaviors of the fault currentlimiters.
sUPERCONDUCTIVE CYLlNDER
We studied the limiting characteristics of twosuperconducting fault current limiters (1) a Bi2223 bulkcylinder [9] and (2) a Bi2212 thick film cylinder. We chosethe Bi2212 thick film cylinder, because it was easier tomake large-scale cylinders. Design parameters for boththe cylinders are given in TABLE I. The Bi2223 cylinderwas made by cold isostatic pressing. The Bi2212 cylinderwas made on a MgO substrate by a thick film processingtechnique. The length of the both cylinders was 70 mm.The Bi2223 cylinder was 50 mm in outer diameter and 5mm in thickness. The Bi2212 cylinder was 50.4 mm inouter diameter and 0.2 mm in the thickness ofsuperconductor
AC MAGNETICSH ELDING
We examined the AC magnetic field shieldingperformances of the both cylinders. The applied fieldwas generated by the winding on the cylinder. The windingwas a covered copper wire of 1 mm in diameter. Thewinding part extended for 60 mm, with two layers of 113turns. The frequency of the applied field was 50 Hz.

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