The operation of power systems can be divided into
the states normal, alert or emergency (Kundur,2014). The system normally
operates in the normal state, but enters the alert state if the system cannot
be expected to be robust to the contingencies that have been considered in the
design of the system. Such situations may occur for example due to unexpected
load increase or outage of some component, such that a single contingency may
force the system into the emergency state. The system enters the emergency
state if a severe enough contingency occurs, so that the system will experience
instability or exceeds operational limits unless emergency control actions are
taken. However, the system is still synchronized in the emergency state.
the states normal, alert or emergency (Kundur,2014). The system normally
operates in the normal state, but enters the alert state if the system cannot
be expected to be robust to the contingencies that have been considered in the
design of the system. Such situations may occur for example due to unexpected
load increase or outage of some component, such that a single contingency may
force the system into the emergency state. The system enters the emergency
state if a severe enough contingency occurs, so that the system will experience
instability or exceeds operational limits unless emergency control actions are
taken. However, the system is still synchronized in the emergency state.