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Spray pyrolysis was used to fabricate TiO2-Ag composite powders for application in oxide barrier between filaments of superconducting multifilamentary tapes. The powders were prepared from an aqueous solution of TiO2 sol and AgNO3. SEM and TEM observations revealed that the average size of the synthesized powder was less than 1ƒÊm and consisted of well-dispersed fine primary particles of TiO2 and Ag. It was clearly ob served that the microstructure of the particles was altered by conditions of heat treatment.

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For the optimization of electrical insulation design for High Temperature Superconducting (HTS) cable, evaluation of electrical insulation characteristics especially for butt gap of LN, impregnated cold dielectric (CD) which consists of the wrapped tape insulation impregnated with LN, plays an important role. This paper presents partial discharge (PD) inception and breakdown characteristics in LN, impregnated butt gap model which modeled a weak point of the wrapped tape insulation impregnated with LN, and cable model with short length with polypropylene laminated paper (PPLP"), Nomex" paper and cellulose paper. PD current pulse was found to have a steep rise time ofns and amplitude oftens FA at PD inception voltage region. Little dependency of breakdown stress on the insulating material is found. PD inception stress is almost independent of insulation thickness of 1 to 3 mm. The requirement insulation thickness for 66 kV class HTS cable is estimated to be -5 mm under PD-free condition from viewpoint of long-term reliability.Index Terms -Partial discharge, breakdown, high temperature superconducting cable, liquid nitrogen, butt gap, cold dielectric, wrapped tape insulation, PPLP, Nomex" paper, cellulose paper, insulation design.

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