###### Abstract  
Superconducting fault current limiters (SFCL) can be an alternative to conventional devices limiting short-circuit currents in power systems. SFCL use high-temperature superconducting tapes of the second generation (HTS 2G) in SFCL, which, after reaching the characteristic critical current of the tape, go into the resistive state (quenching), limiting the short-circuit current. The critical current determines the moment of activation of the SFCL. Therefore, its value should not change during the operation of the device due to repeated limitation of short-circuit currents. The constancy of the critical current is a prerequisite for proper cooperation with the power system protection devices. Multiple quenching can cause microdamage in the superconducting layers responsible for lowering of the value of the critical current of the HTS tapes. The article presents the research results on the degradation processes of 2G HTS tapes intended for the construction of SFCL due to the action of prospective short-circuit currents with values exceeding the critical current of the tested tapes. The decrease in the value of the critical current of the HTS tape as a result of multiple transitions to the resistive state was investigated. The amount of energy emitted during the test current pulse of 0.2 s duration was determined. The limitation values of the voltage drop on the tape, which does not cause accelerated degradation processes, were defined. The microstructural tests of cross-sections of new HTS tapes subjected to prospective short-circuit currents were performed. superconducting tapes; superconducting fault current limiter +
Footnote †: journal: Applied Sciences  
The most prospective device is the SFCL because its main advantages are fast response, no need for additional/external control or fault detection signal, and no steady state losses [3; 4; 7]. High-temperature superconductor (HTS) tapes are applied in SFCL. HTS is a material characterized by zero resistance for a superconducting state, which gives near-zero resistive losses or, in other words, reduces the energy losses significantly. This advantage means that this material is used to construct cables [10; 11; 12], transformers [13; 14; 15], electrical machines [16; 17], and fault current limiters [18; 19]; dozens of projects/applications have been developed/tested for several decades. Modern HTS devices are expected to displace some conventional ones in the future. However, to achieve this, the reliability of the cooling system should be improved, and the cost of HTS should be lower [20]. In addition, superconducting cables, transformers, and electrical machines should operate only in the superconducting state--the ideal situation. Unfortunately, a short-circuit current can jeopardize the proper operation of HTS devices (transition to the resistive state, very high temperature), and such cases should be carefully analyzed. These devices should be designed and/or protected to remain an appropriate functionality even during a fault. The situation is different with a fault current limiter device, which is designed to transition quickly to the resistive state (quenching) (during a short circuit) at a specific instantaneous short-circuit current value, called the critical current \(I_{C}\). Some SFCL prototypes have been successfully tested in a real MV power system [4; 18] and even HV [19]. The literature describes the application of SFLC in many places of the power system, such as:  
* Generator or transformer feeder, busbar coupling, and power plant auxiliaries. It brings the following benefits: improvement in stability and circuit breakers, and switchgear components do not need to be replaced [21];
* DFIG-based wind turbine, virtual power plant. It brings the following benefits: improved fault ride-through capability; the rotor side converter is protected against too much current during any faults; and it helps to meet the grid code requirements [22; 23; 24];
* HVDC transmission system.