In this paper, we propose a model to solve the transmission expansion problem related to the large-scale introduction of renewable energies. The extensive adoption of renewable energies into electricity grids requires the expansion of transmission lines for which companies would need to invest in renewable energy generators. In our proposed model, the expenses incurred in setting up the transmission lines would be covered by the transmission fees charged for the generators. Our model involves optimizing the facility installation and determining the optimal supply-demand operations. However, supply generators would need to compete among themselves with differing cost structures based on the merit-order principle. The investment decisions place the capacity constraints at the operational level where the network may encounter congestion giving rise to different equilibrium prices at the various nodes.