Which scenarios could lead to planned automatic load shedding?

Planned automatic load shedding is typically implemented to preserve the stability of the power grid during abnormal conditions. The scenario that involves low frequency and low voltage is particularly significant because it indicates that the system is experiencing under-frequency or under-voltage conditions, which can pose serious risks to the integrity and reliability of the electrical grid.

When frequency drops too low, it's an indication that supply is falling behind demand, which can lead to a grid collapse if not managed. Similarly, low voltage often suggests that there is not enough reactive power on the system to support the load, which could lead to equipment damage and other operational issues. In these cases, to maintain stability, load shedding is initiated as a preemptive action to reduce demand and help restore desirable operational conditions.

In contrast, the other scenarios involve conditions that do not typically lead to planned load shedding in a similar way. While high frequency or over generation can lead to other corrective actions in a power system, they do not directly imply the urgency that low frequency and low voltage scenarios do, where load shedding becomes a necessary response to stabilize the system.