In restructured electricity markets, network planning has a crucial role over power systems. The network planner must not only coordinate supply and demand in the short run, but also minimize investment and operational costs in the long run. However, power systems present uncertainties making hard a long-term planning of transmission investments in a deregulated
environment.

In this context, we propose a network planning methodology for electricity markets, based on a robust-optimization approach, which considers generation capacity uncertainty. In particular, we propose a robust network planning that considers the uncertainty in the time when new power generation plants are plugged into the power system. We illustrate our methodology using both a 3-nodes network and a 33-nodes stylized version of the main Chilean grid.