Power system is an indivisible whole. So when failures to
one branch happen, the transmission of power will be borne by
the other branches. But electrical equipments of the system
have limited constraints. When the network topology changes
because of the previous electrical equipment failure, the
distribution of flow in the system will definitely changes and
other electrical equipments will inevitably be affected. When
the influence extends beyond the constraints of themselves,
this will surely expand the failure and endanger the security
and stability of the system.
It is difficult to quantify the correlation between branches
caused by season, geography, environment and other factors.
Generally, we can only get an estimate value according to the
statistical analysis and experience. The correlation mentioned
in this article is mainly caused by the flow re-distribution after
the branch broken.
This article is based on the system with enough smart
switches and perfect secondary equipments.