## 5 Ampacity of Overhead Transmission Lines in Slovakia Applying CIGRE Technical Brochure 601  
In practical scenarios, following the guidelines outlined in Slovak standards STN EN 50341-2-23 [23], the conductor's maximum permissible current value at its highest design temperature is utilized within the designated parameters:  
* Ambient temperature \(T_{\text{a}}\) of +35 \({}^{\circ}\)C;
* Wind speed \(V\) of 0.5 m/s at an angle \(\theta\) of 45 \({}^{\circ}\) to the axis of the conductor;
* Global solar radiation intensity \(I_{\text{T}}\) of 1000 W/m\({}^{2}\);
* Absorption coefficient \(\alpha_{\text{s}}\) of 0.5;
* Emissivity coefficient \(\varepsilon_{\text{s}}\) of 0.5. One of the most prevalent types of conductors employed in overhead transmission lines are ACSR conductors, which can be installed individually or bundled together depending on the voltage rating. Table 2 presents the essential technical characteristics of selected ACSR conductors necessary for analyzing and computing the maximum allowable current value based on varying climatic conditions. In this analysis, we also consider a maximum permissible conductor temperature \(T_{\text{s}}\) of 80 \({}^{\circ}\)C and an altitude \(y\) of 208 m.  
The static ampacity of the described conductors encompasses the conditions outlined in the referenced standards. As previously stated, this value remains constant throughout the entire period or year. To simplify matters, the static ampacity is presented for a 24 h interval, as depicted in Figure 3. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Type of Conductor** & **243-AL1/39-ST1A** & **352-AL1/59-ST1A** & **382-AL1/49-ST1A** & **429-AL1/56-ST1A** & **445-AL1/74-ST1A** & **Type of Conductor** \\ \hline Conductor diameter & & & & & & \\ (mm) & 21.75 & 26.5 & 27.0 & 28.7 & 29.7 & \begin{tabular}{c} Conductor diameter \\ (mm) \\ \end{tabular} \\ \hline Diameter of the aluminium wire & & & & & & Diameter of the aluminium wire in the aluminium conductor (mm) & 3.45 & 4.0 & 3.0 & 3.75 & 4.5 & \
\begin{tabular}{c} Diameter of the aluminium wire in the aluminium aluminium \\ wire in the aluminium \\ conductor \\ conductor \\ (mm) \\ \end{tabular} \\ \hline Electrical resistance & & & & & & & & \\ of the conductor & 0.1181 & 0.0816 & 0.0650 & 0.0674 & 0.0758 &
\begin{tabular}{c} Electrical resistance resistance \\ resistance of the conductor \\ (\(\Omega\)/km) \\ \end{tabular} \\ \hline Thermal coefficient & & & & & & (\(\Omega\)/km) \\ of resistance & & & & & \\ (K\({}^{-1}\)) & & & & & \\ \hline The absorptivity of & & & & & \\ the surface & & & & & \\ of the conductor & & & & & \\ (–) & & & & & \\ \hline Emissivity coefficient & & & & & \\ of conductor surface & & & & & \\ (–) & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical specifications of the analyzed ACSR conductors. Figure 4 illustrates the relationship between the maximum permissible current value across various types of ACSR conductors and the ambient temperature. As the conductor diameter increases, its ampacity experiences proportional growth. Conversely, as the ambient temperature rises, the ampacity diminishes. When comparing SLR and DLR, it can be stated that with a change in ambient temperature, while maintaining other conditions according to the STN standards, DLR is advantageous in 93% of cases. The graph depicted in Figure 5 illustrates the correlation between the maximum allowable current value for various types of ACSR conductors and the wind speed, while adhering to the meteorological parameters specified in the STN for SLR. In this graphical relationship, SLR is advantageous in only 5% of cases. Similarly, as the conductor diameter increases, the ampacity experiences a positive increment. The graphical visualization in Figure 6 demonstrates the correlation between the maximum allowable current value of different ACSR conductor types and the wind direction, while maintaining other static weather conditions according to the SLR norm. The conductor diameter positively influences the ampacity.