Design of a 110-kV 2.0-kA SmartCoil Superconducting Fault Current Limiter

The concept of a SmartCoil fault current limiter consists of a conventional primary winding at room temperature, which induces a current in the secondary superconducting winding. This arrangement allows to retrofit an air-core reactor with secondary, short-circuited high-temperature superconducting tapes. This work investigates the designs of a 110-kV 2.0-kA SmartCoil fault current limiter, which reduces the prospective fault current of 13–4.5 kA. In the design process, the geometric dimensions of the primary winding and the number of the superconducting rings in the secondary coil are varied. Key optimization criteria are to keep the stray reactance between 1% and 5% while the impedance during short-circuit conditions must be in the range between 20% and 40%. An excessive heating of the superconductors must be avoided. Transient simulations are also carried out to verify all the performance requirements are fulfilled. Finally, a design proposal with three limiter modules in series with all parameters, including heat input and cooling, is presented. The design meets all requirements by the distribution system operator.