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Selection of the applicable 2G superconducting tapes for transformer windings allows the use of a superconducting transformer to limit short-circuit currents in a power network and significantly reduce wear and tear of circuit breakers and other substation power equipment. In this case, the superconducting transformer can be regarded as an impedance coil whose impedance depends on the operating conditions of the superconducting windings. The impedance of the transformer in the superconducting state is small, equal to reactance of the superconducting windings. After a quench, which is caused by the growth of the short-circuit current, the impedance of the transformer increases, due to appearance of additional superconducting windings' resistance. The level to which the fault current is limited by the superconducting transformer depends on the operation characteristics of the superconducting windings and their construction and also on the parameters of the HTS tape used. This article presents the impact of the technical and operating parameters of commercially available 2G HTS tapes on the value of transformer's impedance after a quench. An example analysis was performed to compare the short-circuit impedance and steady-state fault currents of a conventional copper transformer with a superconducting transformers of equal nominal power.