Effect of HTS tape resistive layers cross-sectional area on the inrush current waveform of a 13.8 kVA transformer

Abstract

Under certain circumstances, when inrushing a superconducting transformer into the power grid, a current many times the rated current of the device may flow. This current can interfere with the operation of the power grid and the equipment connected to it including transformers. The value of the inrush current and its duration is strongly influenced by the resistance of the windings of the transformer being switched on. In normal operation, the superconducting windings of the transformer have zero resistance. As a result, the inrush currents of superconducting transformers reach higher values and longer durations compared to transformers with copper windings. It is possible to build a superconducting transformer that exhibits the ability to dampen the inrush current. This requires designing the windings to be capable of losing and recovering the superconducting state without the risk of damage due to dynamic forces and temperature rise. The resistance of superconducting tapes in the resistive state is crucial. This resistance largely depends on the structure of the superconducting tape used in their construction. The type and cross-sectional area of the resistive layers of the tape have a large influence on this resistance. This paper analyses how changing the thickness of these layers affects the suppression of inrush current.