A New Type of DC Superconducting Fault Current Limiter

A new type of Superconducting Fault Current Limiter (SFCL) for dc applications is proposed. This SFCL consists of a current transmission/limiting coil, an iron-core, and a set of superconductor rings. The superconductor rings are placed between the current transmission/limiting coil and the iron-core. For application, the current transmission/limiting coil is connected in series to a dc transmission line. During normal power transmission, magnetic flux coupling between the current transmission/limiting coil and the iron-core is prevented by the magnetic shielding of the superconductor rings, and the current transmission coil has low impedance. Because of shielding effect of the superconductor rings iron-core has high permeability at the beginning of short circuit, current-limiting coil can effectively limit fault current rise. When the fault current reaches a certain level, the superconductor rings will quench and the shielding effect is greatly reduced. The current-limiting coil strengthens the coupling with the iron core, increases the inductance, and will suppress the further increase of the fault current. A laboratory proof-of-concept prototype was made to demonstrate the feasibility of the idea. Experiments have been carried out with the prototype. In this paper, we will introduce the detailed information of the principle, the prototype, and the experimental results. In addition, a design of the new type of dc SFCL is installed in a ±160 kV high-voltage direct current system.