Title: Resilient Transmission Grid Design: AC Relaxation vs. DC approximation,
Abstract: As illustrated in recent years (Superstorm Sandy, the Northeast Ice Storm of
1998, etc.), extreme weather events pose an enormous threat to the electric
power transmission systems and the associated socio-economic systems that
depend on reliable delivery of electric power. Besides inevitable malfunction
of power grid components, deliberate malicious attacks can cause high risks to
the service. These threats motivate the need for approaches and methods that
improve the resilience of power systems. In this paper, we develop a model and
tractable methods for optimizing the upgrade of transmission systems through a
combination of hardening existing components, adding redundant lines, switches,
generators, and FACTS and phase-shifting devices. While many of these
controllable components are included in traditional design (expansion planning)
problems, we uniquely assess their benefits from a resiliency point of view.
More importantly, perhaps, we evaluate the suitability of using
state-of-the-art AC power flow relaxations versus the common DC approximation
in resilience improvement studies. The resiliency model and algorithms are
tested on a modified version of the RTS-96 (single area) system.