  Cascading failures are one of the main reasons for blackouts in power
transmission grids. The topology of a power grid, together with its operative
state determine, for the most part, the robustness of the power grid against
cascading failures. Secure electrical power supply requires, together with
careful operation, a robust design of the electrical power grid topology. This
paper investigates the impact of a power grid topology on its robustness
against cascading failures. Currently, the impact of the topology on a grid
robustness is mainly assessed by using purely topological approaches that fail
to capture the essence of electric power flow. This paper proposes a metric,
the effective graph resistance, that relates the topology of a power grid to
its robustness against cascading failures by deliberate attacks, while also
taking the fundamental characteristics of the electric power grid into account
such as power flow allocation according to Kirchoff Laws. Experimental
verification shows that the proposed metric anticipates the grid robustness
accurately. The proposed metric is used to optimize a grid topology for a
higher level of robustness. To demonstrate its applicability, the metric is
applied on the IEEE 118 bus power system to improve its robustness against
cascading failures.
