The present-day development of the electric energy industry, the main goal of which is to ensure uninterrupted and standard-compliant supply of electricity to consumers, is based on the emergence of powerful, multi-branched power systems, which encompass large power plants, internal and intersystem power transmission lines and a wide distribution network. As can be seen, one of the main elements of power systems is overhead power lines, the role of which in the development of the future power industry is increasing at a high rate, since the expansion of the power network will be needed both country-wide and internationally. The demand for electricity is growing steadily, therefore, considering that in 2030, all the currently planned cross-border connections will be in use, for example, Estlink 2, NordBalt, LitPol and the ”Kurzemes Ring”, it is already necessary to develop, implement and apply at the existing power transmission networks new technologies since the implementation of the new electrical connections, the significant impact of renewable power resources, the liberalization of the energy market and the construction of nuclear power plants will result in a significant increase in the transit power flow loading of the Baltic transmission networks. Also, it has to be pointed out that a high percentage of all the power transmission lines that are currently in operation have been constructed 40...60 years ago, which is an indication of the power transmission network being outworn and obsolescent, which in turn requires introduction of additional renewing measures. This results in the emergence of many purposeful tasks, which are directly related to the increasing of the capacity of power networks, by ensuring reliable and high-quality power supply to the consumers. In view of the above considerations, it becomes topical to solve the discussed problems by promoting the possibilities to increase the throughput capacity of power networks by offering and implementing a number of high-voltage power line optimization methods, which have been formulated and developed within the present thesis. By using the developed technical and economic solutions, it will be possible to increase the capacity to be transmitted over the existing overhead power lines and those under design (determination of the hidden capacity reserve), by precisely and speedily adopting the correct decision at various cases of existing power transmission network problems, resulting in minimization of capital investments.