DC Magnetization System for a 35 kV/90 MVA Superconducting Saturated Iron-Core Fault Current Limiter

A dc magnetization system, comprises a HTS dc bias coil, a current source, a high-speed switch, and an energy release circuit, was built for a 35 kV/90 MVA saturated iron-core fault current limiter to enhance its functional capability and reliability and to reduce its size and weight. The dc bias coil is made of high temperature superconducting silver sheathed Bi-2223 tapes with a magnetization capacity of 141,000 ampere . turns. The current source is able to supply a maximum of 350 A constant current. The energy release circuit was designed to quickly discharge the magnetic energy of the saturated iron cores and to suppress the voltage surge across the dc coil when the magnetization circuit was switched to open in a short-circuit event. This controllable magnetization system enables the fault current limiter to respond to a short-circuit fault in one millisecond, to reach full current limiting function in 5 milliseconds, and to re-saturate the iron cores in 800 milliseconds after the clearance of a fault. In this paper, we introduce the configuration and specifications of the system. Some experimental results are also reported.