To make better use of the transmission capacity of the traction power supply system, the static temperature increasing and dynamic capacity increasing schemes are introduced into the traction network to tap the transmission potential of transmission lines. Aiming at the reliability problem of line capacity increasing, the capacity increasing scheme of traction network considering the time-varying characteristics of wind speed is studied. In this paper, the risk assessment scheme of medium-term capacity increase based on the Monte Carlo test and the calculation method of safety time of static temperature rise and capacity increase is proposed. The influence of time-varying characteristics of wind speed on the reliability of the existing physical capacity increase system is effectively evaluated, and the temperature change process of the transmission line is analyzed. The “thermal inertia” is used to conduct emergency capacity increase of traction network to save scheduling optimization time. The example shows that the method proposed in this paper is a new and effective method, which is of great significance to tap the transportation potential of the existing traction network.