Increased penetration of renewable energy leads to increased challenges for the Transmission System Operators (TSOs) to operate their system in a secure way. Through the limited means available to the TSOs to manage power flows in the system, reliability is jeopardized. Reliability must be managed differently, replacing the current ways of reliability management
which fails as uncertainty increases.
In this paper a novel risk-based approach of system operation is proposed that can be helpful for the TSOs to assess the confidence of system operation day-ahead, that is, the probability of the forecasted system to end up in an insecure state is calculated. This paper only focuses on violation of power flow constraints in the system. It also demonstrates the increase of this operation confidence using already installed Power Flow Controlling devices. It is shown that these devices aid in enhancing confidence of system operation by shifting power flows to a more optimal one in the light of generation uncertainty. The main emphasis is laid on preventive action. The proposed approach is demonstrated on test systems.