After a disturbance, what action should be taken if 40% of the load is intact but frequency is declining?

In the context of electrical systems, after a disturbance, maintaining system stability is critical. If 40% of the load remains intact but there is a decline in frequency, it indicates an imbalance between generation and consumption. This decline typically signals that the generation capacity is insufficient to meet the existing load demand.

Shed load is the appropriate action to take in this scenario because it helps restore balance to the system by reducing the demand. By intentionally disconnecting a portion of the load, the system frequency can stabilize, decreasing the risk of a more severe overload condition or potential system collapse. This is particularly important in ensuring that the remaining infrastructure can handle the adjusted load without further frequency deterioration.

Generally, while it might seem logical to purchase additional interchange power or attempt to increase load, these actions would exacerbate the existing imbalance in the presence of declining frequency. Similarly, the option to "defeat your AULS" (Automatic Underfrequency Load Shedding) would contradict the goal of stabilizing frequency and could lead to further operational issues. Hence, shedding load strategically is the most effective and immediate response to improve system reliability following the disturbance.