What values change instantaneously during a sudden loss of a large block of load?

• A. Actual Net Interchange
• B. Scheduled Frequency
• C. Scheduled Net Interchange
• D. Area Control Error

Answer: (C)

The correct answer reflects that during a sudden loss of a large block of load, the values that change instantaneously are related to how the system’s balance of generation and consumption is affected. Scheduled Net Interchange refers to the predetermined amount of power exchanged between different areas or entities within the grid. When a significant load is lost suddenly, the immediate impact is that the net interchange may be adjusted to reflect the new balance, which is critical for maintaining system reliability.

In contrast, Actual Net Interchange represents the real-time measurement of the power flowing across interconnections, which may take a moment to settle after such a disturbance. Scheduled Frequency does not change instantaneously; it typically requires changes in generation output to correct frequency deviations caused by the sudden load loss. Area Control Error is a measurement of how well the actual generation meets the scheduled generation, which involves a control response rather than an instantaneous change, as it adjusts based on overall system conditions over time.

Therefore, the correct answer highlights the immediate response of Scheduled Net Interchange to changes in system load, underscoring the importance of maintaining system balance in real-time operations.