  This paper describes an area decomposition and a robust optimization strategy
for the planning of large-scale transmission networks considering uncertainty
in variable renewable energy (VRE) and hydropower generation. The strategy is
illustrated with a study of Brazil's power grid expansion from 2027 to 2036.
The country's network has over 10 thousand buses and 14 thousand circuits and
covers an area equivalent to the USA. A clustering scheme based on bus marginal
costs is used to decompose the grid into seven regions. Each regional planning
is then solved by a heuristic and Benders decomposition methods to produce a
robust least-cost plan for 3,000 dispatch scenarios.
