Tests of the 15-kV Class Coreless Superconducting Fault Current Limiter

This paper presents the design and tests of a superconducting fault current limiter (SFCL) for medium voltage as a device allowing for a more effective use of the existing power network infrastructure. The limitation of short-circuit currents by the SFCL to safe levels will result in the network elements being susceptible to smaller electrodynamic and thermal overloads. The application of an SFCL leads to an increase of the allowable short-circuit power at the point of connection of new power generating sources, which is determined by the short-circuit parameters of the power network. This, in turn, will result in an increase of the capability of the power network for connecting distributed generation energy sources based on renewable energy sources. Light and compact construction of the coreless SFCL consists of three magnetically coupled windings cooled in liquid nitrogen: primary and secondary windings, made of HTS 2G tape, and a parallelly connected primary copper winding. A high magnetic coupling between the superconducting primary and secondary windings gives a low voltage drop on the limiter at a nominal current. The presented solution reduces the size and the weight of the device. Tests performed at a high-power test facility show the limiting performance of the coreless inductive SFCL.