## 8 Results of the Parametric Analyses Carried Out with the Proposed Tool
### Impact of the Cable's Voltage Level  
In this study, a 50 km-long cable with a rated maximum power of 1 GW was connected to a load with a \(cos\varphi\) equal to 0.9. For this parametric analysis, the tool compared different voltage levels selected by the authors among those considered most significant. Since a precise classification of HVAC levels is not well defined globally, the authors chose to investigate some known maximum and minimum limits. For example, 220 kV is considered the maximum limit for high voltage-class lines in several parts of Europe [(69; 70)], while higher voltages are classified as extremely or extra-high voltages. Extremely high voltages were excluded from this investigation as they tend to complicate the construction of a transmission line and do not fully exploit the high-current capabilities of superconducting materials. The results shown here for the 220 kV case clearly coincide with those presented in the previous section for the same case. The lower limit of this parametric analysis was set equal to the lower limit for high voltage-class lines according to American standards: 115 kV [(71)]. To be consistent, the corresponding frequency value was also adjusted to 60 Hz to follow American regulations. Additionally, some intermediate values, such as 132 kV (the level used in various countries, including the UK) and 150 kV (the level used in various countries, including Switzerland), were selected. Figure 15 illustrates the capital cost contributions per unit cable length for the various voltage scenarios described. As expected, for the same power level, capital costs increased as the voltage decreased, with the 115 kV case incurring 53% higher investment costs than the 220 kV case. However, it is important to note that the cost calculation did not account for certain devices, such as transformers, for which no techno-economic correlation was found. These devices typically have costs proportional to the voltage level they need to handle and can impact the overall budget. Figure 14: Liquid nitrogen mass flow rate, varying the maximum active power transferred. The cases considered had \(V_{rms}=220\) kV, \(cos\varphi=0.9\), and \(L_{line}=50\) km. The main index cost increase corresponded to the HTS tapes, which were needed in greater quantities as the voltage decreased. Specifically, the number of overlaying layers composing phase 1 (\(nl_{3}\)) was equal to three for the 115 kV case, \(nl_{3}\) = 2 for the 132 kV and 150 kV cases, and \(nl_{3}\) = 1 for the 220 kV case, leading to a nearly proportional number of tapes in phase 1. While the outer phases in the lower-voltage cases still consisted of a single layer, these tapes had to carry significantly more current, prompting the solver to use higher-performing and more expensive coated conductors. The insulation cost remained relatively constant across different cases, since the thickness of the insulating layers did not vary significantly when changing the voltage. This \"unexpected\" regularity was due to theses thicknesses being mainly determined by the requirements for managing the lightning impulse conditions and not the AC nominal voltage levels. Different user-defined parameters in Section 7.2 might reach different conclusions. Then, Figure 16 shows the contributions to the operating costs per unit length of the line, calculated over the entire cable lifespan, for the same voltage cases as those in Figure 15. As concluded for the parametric analysis carried out in Section 8.1, the operating costs were primarily due to the losses managed by the cooling system. These losses increased as the voltage level decreased because the operating current rose proportionally at fixed transport power values. However, the losses did not increase linearly with the current, which was particularly significant in the 115 kV case.