Modeling of Shield-Type Superconducting Fault-Current-Limiter Operation Considering Flux Pinning Effect on Flux and Supercurrent Density in High-Temperature Superconductor Cylinders

Superconducting fault current limiter, SFCL, forms an important category of fault-current-limiting devices which limit the short-circuit current levels in electrical networks. Therefore, modeling its operation and anticipating its characteristic parameters are too important in its design and optimization process. In this paper a novel integrative method has been proposed which predicts, with a good accuracy, the behavior of inductive shield-type SFCL in different circumstances and approximates its main operational characteristics, as the through current, the inductance and the voltage-current characteristics. An algorithm is presented to calculate the exact distribution of magnetic flux and supercurrent density inside the superconductor bulk in different operational conditions using the well-known Bean model and for the first time the flux pinning effect has been taken into account in SFCL operation modeling. For estimation of flux density distribution outside the superconductor bulk, the FEM analysis has been utilized. An iterative method has been used, based on the numerical solution of differential equations, to calculate the instant value of the SFCL through-current and inductance. The proposed method of modeling has been studied on a specific design of shield-type SFCL and its through current in normal and fault conditions of a test circuit, variation of its inductance with time and its voltage-current characteristic are calculated theoretically. A prototype has been fabricated based on the studied SFCL design and has been tested experimentally. The comparison of the experimental and theoretical results shows that this modeling predicts the SFCL operation with a good accuracy.