Electromechanical Analysis of Core- and Shell-Type Inductive Superconducting Fault Current Limiters Under General Fault Conditions

In transmission and distribution grids, electrical currents in rated conditions can reach hundreds of amps. Under fault conditions, these currents can reach ten times or more their rated value. In power devices, particularly in superconducting fault current limiters (SFCLs), this current rise leads to the development of electromechanical forces that can damage the superconducting tape, so should be properly analyzed, for the sake of equipment integrity. Additionally, when asymmetric faults occur in the grid, the desired circumstance is that a fault in one phase does not affect the other ones, to minimize damages and disturbances in the grid and protection devices. In this article, core- and a shell-type inductive SFCLs are tested under several fault conditions. The main objectives are to measure and analyze the electromechanical forces developed in each superconducting winding, to evaluate their integrity after faults, and to compare the performance of both types of limiters under the same fault conditions. Electromechanical forces measurements in the three phases are made simultaneously, using a device based on strain gauges, calibrated to operate at 77 K. This article contributes to evaluating the robustness and best geometry of this inductive limiter of transformer type.