| stable state in which some system components are stressed beyond their ratings, or some bus voltages or system frequency are outside tolerances|
Figure 2 – Electric power system states
NOTE The arrows indicate the most important state transitions caused by credible events. Recovery transitions, in opposite directions, are effected by operator intervention.
Figure 3 – Examples of transitions within electric power system states
Figure 6 – Examples of electric power system states and corresponding system operation status
Note 1 to entry: In an emergency state, urgent actions (such as load shedding; reducing voltage; and starting emergency generators) are required to prevent equipment damage and/or further degradation of system state.
Note 2 to entry: Although loss of load can occur, it is not a criterion for an emergency state.
Note 3 to entry: This entry was numbered 191-22-05 in IEC 60050-191:1990.