  The transmission system operators (TSOs) are responsible to provide secure
and efficient access to the transmission system for all stakeholders. This task
is gradually getting challenging due to the demand growth, demand uncertainty,
rapid changes in generation mix, and market policies. Traditionally, the TSOs
try to maximize the technical performance of the transmission network via
building new overhead lines or physical hardening. However, obtaining public
acceptance for building new lines is not an easy step in this procedure. For
this reason, the TSOs try to capture the capabilities of existing assets. This
paper investigates the use of modular FACTS devices (to alter the line
characteristics) for improving the capability of transmission network in
serving the uncertain demand without the need for building new overhead lines.
The proposed method considers the uncertainty of demands and controls the
utilization of existing transmission assets. The mathematical results obtained
are validated with a complete non-linear simulation model of three transmission
networks.
