The following pages depict the evolution of a simulated
failure of the Eastern Interconnect, one of three large-scale transmission grids in the United States, with tens of thousands buses (nodes) and lines (arcs). The cascade is initiated by disabling two high
power flow lines.
We evaluate a cascade
according to three criteria:
the yield, which is the percentage of
total demand still satisfied after the grid becomes stable
the time taken until the grid
becomes stable. We measure time in 'rounds'
the number of lines that become
outaged during the cascade.
We study two cases of the
cascade. In one case the cascade is uncontrolled, that is to say,
no action is taken and the cascade is allowed to run its course. In the
second case the cascade is governed by an affine, adaptive
load-shedding control. The control is constrained
in two ways:
demand can only be shed in
rounds 1 - 10 of the cascade, using time-dependent affine scaling rules
(see references below).
if at the end of the 20th round
some lines are still overloaded, then an 'emergency' load shedding is
carried out so as to remove all overloads.
material is found in this report (a short version, here).
This work was funded by DOE grant DE-SC000267.
The uncontrolled cascade becomes stable in the 34th round with a yield
of approximately 78% and 4425 outaged lines. The control
we consider in these pages is approximately optimal subject to the
above constraints. It sheds load in rounds 2 and 7 only; it achieves stability at
the 19th round with a yield of approximately
75% and 2598 outaged lines.
In the pictures, outaged lines are shown in black. The geometric
layout of the grid was not obtained using actual coordinates
(unavailable) but was instead computed using sfdp.