The use of a High-Temperature Low-Sag (HTLS) conductor is one of the most discussed methods of uprating power systems nowadays. This method is more suitable for an uprating solution of power systems, because the optimized HTLS conductors have such advantages as high current capacity, long-term reliability, low sag-tension property, easy and quick installation, and low line loss. To assess the conductors with composite core, their use, a technical and economic comparison with the traditional steel conductors has been made. For comparison purposes, a route in Latvia, Kurzeme region, was chosen. It is intended to construct a ring of 330 kV overhead transmission line there. The goal of new transmission line design is increasing the transmission capacity and voltage level to 330 kV and power supply reliability. Based on the chosen transmission line model, the comparison estimaton was made. The paper deals with a comparative analysis of the mechanical and thermal conditions of HTLS and steel reinforced aluminium conductor (ACSR) based on a particular overhead line model. The obtained calculation results are presented in the paper in graphic and table format.