# DC Cabling of Large-Scale Photovoltaic Power Plants
## 5 Testing of the Model/Case Study
\begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{2}{c}{**HCM78 \(\times\) 9–440 W Solar**} & \multicolumn{2}{c}{**Inverter Parameters**} \\ \hline \(P_{\mathrm{P}}\) & 440 W & \(P_{\mathrm{INV}}\) & 16,000 W \\ \(U_{\mathrm{O}}\) & 53.9 V & \(U_{\mathrm{DC}\mathrm{min}}\) & 320 V \\ \(U_{\mathrm{PN}}\) & 45.56 V & \(U_{\mathrm{DC}\mathrm{max}}\) & 800 V \\ \(I_{\mathrm{SC}}\) & 10.25 A & Efficiency & 98.4\% \\ \(I_{\mathrm{PN}}\) & 9.65 A & \(U_{\mathrm{NN,max}}\) & 750 V, AC \\ \(k_{\mathrm{i}}\) & 0.05 \%/\({}^{\circ}\)C & \(U_{\mathrm{max}}\) & 1000 V \\ \(k_{\mathrm{u}}\) & \(-\)0.29 \%/\({}^{\circ}\)C & & \\ \(k_{\mathrm{p}}\) & \(-\)0.37 \%/\({}^{\circ}\)C & & \\ NOCT & 45 \({}^{\circ}\)C & & \\ Length, \(L\) & 2.172 m & & \\ Width, \(W\) & 1.002 m & & \\ \hline \multicolumn{2}{c}{Plant power, \(P\)} & 3 MW \\ \hline \multicolumn{2}{c}{Location parameters} \\ \hline Geographic latitude & 43\({}^{\circ}\) & \\ Temperature & 35 \({}^{\circ}\)C & \\ Insolation, \(G\) & 1000 W/m\({}^{2}\) & \\ \hline \multicolumn{2}{c}{Orientation and distance of the solar modules} \\ \hline Solar module slope angle, \(\alpha\) & 22\({}^{\circ}\) & \\ Distance between solar modules, \(L_{0}\) & 0.2 m & \\ Distance between modules & 1 m & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Input data of the model. The ambient temperature is \(35\,\mathrm{\SIUnitSymbolCelsius}\), and insolation is \(1000\,\mathrm{W}/\mathrm{m}^{2}\). The power of the inverter is changed from \(5300\,\mathrm{W}\) to \(90,\mathrm{100}\) W in increments of \(5300\,\mathrm{W}\). Under these conditions, the power efficiency of the inverter exceeds \(99\%\). The blue curve denoted by \(p_{1}\) represents the results for cabling with two types of cables. For this cabling method, power losses on the DC cables do not exceed \(0.55\%\). The red-dashed curve (\(p_{2}\)) represents the cabling results with only one type of cable. With increasing power, the losses increase linearly and are larger than those with two types of cables. The maximum value is obtained for an inverter power of \(90,\mathrm{100}\) W and is equal to \(0.71\%\). Table 7 shows the economic parameters of DC cabling for inverters with different power levels. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Two Types of Cables**} & \multicolumn{2}{c}{**One Type of Cable**} \\ \cline{2-7}
**P [kW]** & \multicolumn{2}{c}{\(\mathbf{S_{1},\,4\,mm^{2}}\)} & \multicolumn{2}{c}{\(\mathbf{S_{2}}\)} & \multicolumn{2}{c}{\(\mathbf{S_{1},\,4\,mm^{2}}\)} \\ \cline{2-7}  & \(d\) **[m]** & \(M\) **[kg]** & \(s\) **[mm\({}^{2}\)]** & \(d\) **[m]** & \(M\) **[kg]** & \(d\) **[m]** & \(M\) **[kg]** \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 7: Cable lengths, types, and masses for different inverter power levels. Figure 8: Diagram of power losses on the DC cables as a function of inverter power for both types of cabling. For a topology with two cable types, the S\({}_{1}\) cable is 4 mm\({}^{2}\), with an average cable length of 18.3 km and an average cable copper mass (\(M\)) of 702 kg. The average value of the cable length and the cable copper mass is calculated for the different power inverters, using the values from columns 2 and 3 of Table 7. The S\({}_{2}\) cable has cross-sections ranging from 16 mm\({}^{2}\) to 120 mm\({}^{2}\), lengths ranging from 1 km to 3.3 km, and copper masses ranging from 156 kg to 3815 kg. The one-cable topology uses an S\({}_{1}\) cable with a 4 mm\({}^{2}\) cross-section, an average length of 20.4 km, and an average cable copper mass of 785 kg, where average length and mass values are calculated using columns 7 and 8 of Table 7. Based on the above data, it is possible to calculate the cost-effectiveness of investing in copper to reduce losses. It is necessary to decide between a topology with one type of cable and a topology with two types of cables.