Fault Current Limitation in Power Network by the Superconducting Transformers Made of 2G HTS

The fault current limiting feature of the SC transformer with the HTS 2G windings provide protection and significantly reduce wear and tear for circuit breakers and other substation power equipment. A comparison of the short circuit currents of the 64 MVA transformer wound with copper and YBCO 2G HTS tapes is made in this paper. The results of the analysis show that the YBCO 2G tapes enable to built the superconducting transformer with the ability to limit the short-circuit currents. The superconducting windings require special considerations for the induced electromagnetic forces in order to limit them below the allowable tensile stresses. Strongly anisotropic Y-123 tape used in the winding of the transformer will be exposed to different orientations and amplitudes of the local magnetic field. If the transformer is going to act also as a fault current limiter, the uniformity of the transition of the transformer winding is crucial to avoid sectional responses of the transformer. Therefore it is essential to conduct systematic current-magnetic field measurements to define `constant current domain´ for the conductor at a given operating temperature.