**4. Conclusions and Verifications**

The comprehensive fault current characterization presented in this paper used a simplified, validated SCs model and highlighted the following key outcomes:

The operation of the SCs can be divided into three different stages: (i) the superconducting stage during the steady state operation of a power system, at which the SCs presents approximately zero resistance; (ii) the quenching process, which includes the partial resistive flux flow stage, reached when the fault current exceeds the critical current *IC* and while temperature remains below the critical value *TC*; and (iii) the highly resistive normal state which is reached once the temperature exceeds the critical value *TC*. Furthermore, it has been found that during fault, the stabilizer layer can be used as a parallel path for the transient current, reducing heat generation, temperature rise, and protecting the cable from being damaged. To better investigate the feasibility of the copper stabilizer layer, the change of the copper layer resistivity has been modelled during the normal resistive mode, while the resistance of the HTS layer considered to be constant (i.e., set to its maximum value).

The performance of the SCs in limiting the fault currents was assessed through a number of fault scenarios. Simulation results revealed the impact of SCs on fault current magnitudes, under different type of faults, and as a consequent on the short-circuit level of the power systems. Specifically, it has been observed that within the first electric cycle, the magnitude of the fault current has been reduced from 15 kA to approximately 1.8 kA. Therefore, the installation of SCs introduces a challenge for the existing protection schemes due to their variable resistance, which leads to lower fault currents and higher voltage magnitude during transient conditions. In order to obtain a deeper insight of the fault current limiting capability of SCs, a comparative analysis has been conducted between the SCs and a conventional copper cable under the same fault conditions. The analysis revealed that for 3-Phase-to-g faults, the SCs model offers fault current limitation in the range of 60%, with respect to the prospective values. Therefore, the deployment of SCs increases the transmission efficiency due to the low resistance during the steady state and suppresses fault currents. The obtained results are well-aligned with relevant conducted studies such as [19,36,40].

The performance of SCs during transient conditions is determined by certain power system characteristics such as the prospective fault currents and fault resistance. In particular, simulation results showed that the increase in the fault resistance value impacts on the feasibility of the SCs, as it a ffects the quenching degree. It was revealed that the higher the fault resistance, the lower the prospective current and the percentage of current limitation. This was confirmed through the case of fault resistance equal to *Rf* 3 = 10 Ω, where the fault current is predominately limited by the fault resistance, a ffecting the increase in the resistivity of HTS tapes (which do not enter normal state) and the quenching process.
