| lack of steady-state stability
NOTE 1 – Steady-state instability usually occurs due to excessive power transfers.
NOTE 2 – Under this condition, the derivative of the active power with respect to the angle of deviation between at least one generator's e.m.f. and the reference e.m.f. is negative.
NOTE 3 – A power system is steady-state unstable for a steady-state operating condition if, following any small disturbance, it fails to reach a steady-state operating condition.