Transmission systems are needed to be upgraded based on expected/unexpected load growth factor by years. However, it is not so easy to install and upgrade the transmission system, which requires transmission planning calculation ahead of time. Traditionally, transmission companies built extra transmission lines to meet that load growth, but it is not easy and cost-effective to upgrade the system every time loads increase. Some unexpected load growth may occur for some load points that is not in the part of planning calculation. For those situations, the transmission system may face serious congestion problems. Transmission companies have been looking for a way to control power flow rather than building extra electricity capacity. With the development of technology, more complex and integrated flexible alternating current transmission system technologies that can control power flows by changing the voltage amplitude, the angle, and the impedance of the transmission line are now widely used. Phase-shifting transformer (PST) is one of the most widely used devices that can be used for controlling power flow. PST can vary the amount or direction of the active power flow by injecting voltage at different phases into the transmission line on which PSTs are installed. In this study, possible location case studies of PST in the Turkish transmission network will be investigated. Static analyses will be performed using the PSS/E and Python programs. The maximum and minimum production status of distributed wind power plants will be analyzed comparatively in the energy corridor with PST. Capacity improvement and power flow dispatch from each case study with and without PST will be compared. Finally, we propose a mathematical model to suitably determine the angle of PST in order to minimize real power losses that are caused by PST and provide N-1 security.