Basic Study on Ground Fault Characteristics of 275-kV HTS Cable

The ground fault experiment for the 275-kV high-temperature superconductor cable was conducted in the project “Demonstration studies of the stability and reliability of next-generation transmission systems,” sponsored by NEDO. A short piece of the cable, which had an artificial ground fault point with an iron pin, was stood and poured with liquid nitrogen, and then conducted alternating current for three cycles, 60 ms. As a result, the current flowed in the ground fault path and caused an arc discharge. When the effective current was less than 5 kA, the arc lasted only half a cycle to invert the polarity. When the current was over 5 kA, the samples were damaged severely. The cryostat pipes were vented completely, and the cable cores were cratered deeply.