You are noticing a voltage decline in a weak area of your system. After exhausting reactive resources, what should you do?

The most appropriate response to a voltage decline in a weak area of the system, after reactive resources have been exhausted, is to manually shed enough load to prevent voltage collapse. This action directly addresses the immediate risk posed by low voltage conditions, which can lead to serious reliability issues and potential system failures.

By manually shedding load, operators can decrease the demand on the system, thereby stabilizing voltage levels and preventing cascading failures or outages. This is crucial, especially in weak areas of a system where the voltage is more susceptible to fluctuations due to a lack of adequate reactive power support or strong transmission infrastructure.

In contrast, notifying customers of impending outages could lead to unnecessary panic and is not a proactive measure to address the underlying voltage issue. Automatic undervoltage load shedding may also be a viable option; however, it depends on pre-configured settings, and in an emergency, manual intervention allows for immediate control tailored to the situation. Opening circuit breakers on all three transmission lines could cause unnecessary disruption to service and would not specifically target the voltage problem at hand.

Therefore, the decision to manually shed load is a targeted response designed to promptly mitigate the voltage decline and maintain system integrity.