Transmission network expansion planning considering risk level assessment and scenario-based risk level improvement

Renewable energy sources (RESs) are actively connected with the grid, and thus the requirement for transmission network expansion planning has increased. When RESs are added to the grid as independent power plants under a deregulated power system structure, an independent system operator managing the transmission system should evaluate the impact of RES penetration. The system operator should restrict the capacity of the RES to be installed or perform transmission network expansion planning if necessary. This study proposes risk assessment (RA) based on an exponential risk level (RL) model to evaluate the negative effects of RES penetration and introduces a method of applying RA in scenario-based transmission network expansion planning. The index of RL reduction via a scenario is formulated as an economic efficiency indicator for reducing the RL, based on the result of RA. A case study is performed on an actual power system in South Korea. For two cases based on the penetration of RESs, transmission network expansion planning considering the proposed RA is performed for several scenarios, and then, the best scenario for each case is selected.