  From a stability perspective, a renewable generation (RG)-rich power system
is a constrained system. As the quasistability boundary of a constrained system
is structurally very different from that of an unconstrained system, finding
the sensitivity of critical clearing time (CCT) to change in system parameters
is very beneficial for a constrained power system, especially for
planning/revising constraints arising from system protection settings. In this
paper, we derive the first order sensitivity of a constrained power system
using trajectory sensitivities of fault-on and post-fault trajectories. The
results for the test system demonstrate the dependence between ability to meet
angle and frequency constraints, and change in power system parameters such as
operating conditions and inertia.
