Considering the on-going development of the electricity market, exchange with neighboring power companies, increase in consumption, and the growing share of renewable energy sources in the energy mix, there is a growing need for an electricity network of higher quality and reliability, with inevitable increase in transmission capacity. There is less free space for new overhead lines, it is more appreciated, and it is already common situation for spatial congestions to appear around urbanized areas, industrial zones and large cities when routing new transmission lines and reserving corridors for them. Therefore, an increase in the transmission capacities of the existing overhead transmission network lines is recognized as a quality solution. This thesis deals with the two most significant methods: a) replacement of existing classic ACSR conductors with high temperature low sag (HTLS) conductors; b) increase of the nominal voltage level of transmission line. The methods are analyzed in detail, and here are presented the specifics and criteria that need to be met by applying these methods. In this thesis, an analysis of the technical and economic profitability of these methods is made on a hypothetical example of an overhead transmission line, and a comparison is made with the usual case of building a completely new overhead transmission line. The analysis showed that the mentioned methods are still more attractive for the Investor than the option of building a new overhead line. In any case, both methods imply the importance of previous detailed analyzes and tests in order to achieve the highest quality and most cost-effective solution.