Test of 1.2 MVA high-Tc superconducting fault current limiter

A 3-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 superconducting part consists of a stack of rings made of Bi-2212 ceramic. They were 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-voltage characteristic obeys a power law U similar to I-alpha with alpha approximate to 5. The critical current density defined by the 1 mu V/cm criterion is about 1400 A/cm(2). The nominal current and voltage of the device are 70 A and 10.5 kV, respectively. In 3-phase shea circuit tests with a prospective fault current of 60 kA the current was limited to about 700 A in the first half wave. After 50 ms the limited current was below 250 A. The test results are in excellent agreement with detailed simulations of both the normal operation and the behaviour under fault conditions. The current limiter has been installed in the auxiliary line of a hydropower plant for an one year endurance test. It is the first superconducting device tested in a power plant under actual operating conditions.