## 5 Experimental Results
### Three-Layer, Two-Layer, and Single-Layer ACSR Conductors  
Figure 7 shows the experimental results of \(r_{AC}\) versus temperature for the three ACSR conductors studied. These results were obtained by heating the conductors at different current levels using the experimental setup shown in Figure 5.  
The results shown in Figure 3 show that, as expected, \(r_{AC}\) depends on the current level, but its behavior is very different in three-layer, two-layer, and single-layer conductors. While the dependence of \(r_{AC}\) on the current level is very pronounced in single-layer conductors, this dependence is almost absent in two-layer conductors and very weak in three-layer conductors. This behavior is due to the total cancellation, partial cancellation, or absence of cancellation of the axial component of the magnetic field generated by the different aluminum layers, depending on the number of aluminum layers of the conductor, as explained in Section 3.2.  
Table 3 summarizes the main parameters of the analyzed ACSR conductors. It combines the datasheet values with the calculated values from Equations (4), (5) and (12), and the experimental measurements performed in this work, some of which are extracted from the results shown in Figure 7. The results presented in Table 3 show that the smallest differences between the measured and calculated values of the AC resistance are found in three-layer ACSR conductors, while for two-layer and single-layer conductors the differences are much larger, especially when using Equation (4), so it seems that Equation (5) gives more accurate results than Equation (4). Note that these results are subject to an appropriate choice of the electrical conductivity of the Al strands and, to a lesser extent, of the steel wires, as this is a critical parameter. In addition, Equation (12) is not very suitable for single-layer conductors because the dependence on current is very weak (factor 9\(\cdot\)10\({}^{-8}\)), while experimental tests show that the current level has a large effect on the \(r_{AC}/r_{DC}\) ratio, as shown in Figure 7c.  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Conductor Parameters** & **Values** \\ \hline Number of Al alloy strands & 61 (1/6/12/18/24) \\ Lay ratios [14] & 15/13.5/12.5/11 \\ Diameter of the strands [mm] & 3.45 \\ Measured conductor diameter [mm] & 31.15 \\ Aluminum alloy cross-section [mm\({}^{2}\)] & 570.22 \\ Minimum electrical resistivity of Al alloy [11] & 52.5\% IACS \\ Measured temperature coefficient of resistance, a [\({}^{\circ}\)C\({}^{-1}\)] & 0.00330 \\ Measured \(r_{DC}\) at 20 \({}^{\circ}\)C [u\(\Omega\)/m] & 56.77 \\ Calculated \(r_{DC}\) at 20 \({}^{\circ}\)C [u\(\Omega\)/m] from (3) & 59.34 \\ Calculated \(r_{AC}/r_{DC}\) ratio from (7) & 1.0246 \\ Calculated \(r_{AC}\) at 20 \({}^{\circ}\)C [u\(\Omega\)/m] from (3) + (7) & 60.80 \\ Measured AC resistance per unit length (20 \({}^{\circ}\)C) [u\(\Omega\)/m] & 57.69 \\ Difference between measured and calculated values of \(r_{AC}\) [\%] & \(-\)5.39\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: Main parameters of the Aster 570 AAAC conductor.  
Once again, the electrical conductivity of the aluminum strands plays a critical role since the percentage change in this parameter is directly and proportionally reflected in the \(r_{DC}\) value given by Equations (4) and (5).