TEST OF 1.2 MVA HIGH-T-C SUPERCONDUCTING FAULT CURRENT LIMITER

A three-phase superconducting fault current limiter with a rated power of 1.2 MVA has been built, tested and installed in a power plant. The device is based on the 'shielded iron core concept'. The superconduct ing part consists of a stack of rings made of 81-2212 ceramic. They we re fabricated by a special partial melt process and have a diameter of 38 cm, a height of 8 cm and a thickness of 1.8 mm. The current-voltag e characteristic obeys a power law U similar to I-alpha with alpha app roximate to 5. The critical current density defined by the 1 mu V cm(- 1) criterion is about 1400 A cm(-2). The nominal current and voltage o f the device are 70 A and 10.5 kV, respectively. In three-phase short- circuit tests with a prospective fault current of 60 kA the current wa s limited to about 700 A in the first half-wave. After 50 ms the limit ed current was below 250 A. The test results are in excellent agreemen t with detailed simulations of both the normal operation and the behav iour under fault conditions. The current limiter has been installed in the auxiliary line of a hydropower plant for a 1 year endurance test. It is the first superconducting device tested in a power plant under actual operating conditions.