  Recently, there has been a growing concern about the overload status of the
power grid networks, and the increasing possibility of cascading failures. Many
researchers have studied these networks to provide design guidelines for more
robust power grids. Topological analysis is one of the components of system
analysis for its robustness. This paper presents a complex systems analysis of
power grid networks. First, the cascading effect has been simulated on three
well known networks: the IEEE 300 bus test system, the IEEE 118 bus test
system, and the WSCC 179 bus equivalent model. To extend the analysis to a
larger set of networks, we develop a network generator and generate multiple
graphs with characteristics similar to the IEEE test networks but with
different topologies. The generated graphs are then compared to the test
networks to show the effect of topology in determining their robustness with
respect to cascading failures. The generated graphs turn out to be more robust
than the test graphs, showing the importance of topology in the robust design
of power grids. The second part of this paper concerns the discussion of two
novel mitigation strategies for cascading failures: Targeted Load Reduction and
Islanding using Distributed Sources. These new mitigation strategies are
compared with the Homogeneous Load Reduction strategy. Even though the
Homogeneous Load Reduction is simpler to implement, the Targeted Load Reduction
is much more effective. Additionally, an algorithm is presented for the
partitioning of the network for islanding as an effort towards fault isolation
to prevent cascading failures. The results for island formation are better if
the sources are well distributed, else the algorithm leads to the formation of
superislands.
