  In the second part of this two-paper series, the stability margin of a
critical machine and that of the system are first proposed, and then the
concept of non-global stability margin is illustrated. Based on the crucial
statuses of the leading unstable critical machine and the most severely
disturbed critical machine, the critical stability of the system from the
perspective of an individual machine is analyzed. In the end of this paper,
comparisons between the proposed method and classic global methods are
demonstrated.
