How long does it take to respond to a post-contingency emergency voltage limit?

The response to a post-contingency emergency voltage limit needs to be immediate because voltage stability is critical to the reliable operation of the electrical grid. When a contingency occurs, such as the loss of a transmission line or a generator, the resulting voltage fluctuations can have significant repercussions. These can include an increased risk of equipment damage, potential blackouts, or cascading failures in the system.

Therefore, the protocols in place require system operators to take swift action to mitigate these risks. This may involve redistributing loads, reconfiguring the network, or activating reactive power resources such as capacitors or synchronous condensers to stabilize the voltage levels quickly. The emphasis on immediate action reflects the urgency of maintaining grid reliability and preventing further complications that could arise from delayed responses.

In contrast, the other options suggest a timeframe that would be too lengthy to address emergency conditions effectively, highlighting why immediate response is the appropriate and necessary choice.