## 4 Considerations Relating to the Use of High-Temperature Low-Sag Conductors
* A low thermal expansion coefficient, allowing it to withstand high operating temperatures with minimal thermal elongation, resulting in reduced sag. * Lower electrical resistance, which reduces electrical loss and allows for increased rating. HTLS conductors represent the best solution for upgrading power lines from ACSR and for new high-voltage transmission lines. Reconductoring existing lines with HTLS conductors is a practical approach to significantly enhance power line capacity in the long run. The economic benefits of reconductoring have spurred new studies in this field [4; 5]. Comparative analyses reveal that despite the higher initial installation cost of ACCC conductors, they offer substantial long-term advantages. ACCC conductors reduce line losses more effectively than other HTLS options, ensuring more profitable returns over time. Studies demonstrate the cost comparison between ACSR and ACCC conductors, highlighting the efficiency gains associated with ACCC conductors in terms of current capacity and diameter size. Their lighter weight and ability to operate efficiently at high temperatures also mitigate sag issues, underscoring ACCC conductors as a superior choice for enhancing both the capacity and operational efficiency of power transmission systems over the long term [3; 4; 5]. Based on processed studies in the distribution system, the adoption of HTLS conductors could potentially address the increasing demands for connectivity, power transmission, and distribution between 110 kV substations and nodes. There is a general shift in the conceptual and developmental framework of distribution systems towards employing conductors with larger cross-sections, often necessitating the complete dismantling of existing, often technologically obsolete lines and the construction of new ones [20; 21; 22]. The study results indicate that under appropriate deployment conditions, HTLS conductors could allow for the retention of existing pylon structures. By replacing conductors, this not only increases the transmission capacity but also shortens and reduces the cost of the reinforcement process for the lines [20; 21; 22]. The mechanical and economic benefits of using HTLS conductors are as follows [20; 21; 22]:  
* Using HTLS conductors is 4-times cheaper than dismantling and rebuilding new lines with equivalent current-carrying capacity;
* HTLS conductors cost 1.1 times more than simple conductor replacements but allow for a 1.4-times increase in transmission capacity with less impact on modifying existing support points;
* They shorten the downtime of the line required for capacity reinforcement;
* HTLS conductors with a steel core can be used in areas prone to heavy icing;
* They maximize the lifespan of pylon structures. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Conductor Designation** & **Conductor Name** & **Maximum** \\  & **Collaborable** \\  & **Temperature (\({}^{\circ}\)C)** \\ \hline \hline \multirow{2}{*}{ACSS} & Aluminium conductor, steel & \\  & supported & 200–250 \\ \hline \hline G(Z)TACSR & Gap-type super thermal resistant aluminium alloy, steel & 150–210 \\  & reinforced & \\ \hline \hline \multirow{2}{*}{(Z)TACSR} & Super thermal resistant & \\  & aluminium alloy conductor, steel reinforced & 150–210 \\ \hline \hline \multirow{2}{*}{(Z)TACIR} & Super thermal resistant & \\  & aluminium alloy conductor, invar reinforced & 150–210 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The fundamental types of HTLS conductors and their specifications [9].