How long must a balancing authority maintain an ACE above 100% for compliance?

The requirement for a balancing authority to maintain an Area Control Error (ACE) above 100% for compliance is based on a specific timeframe that aligns with regulatory standards. The correct choice reflects the need to maintain this level for every minute over the past 12 months. This duration is critical for monitoring and ensuring that balancing authorities operate within acceptable limits for reliability and operational performance.

Maintaining an ACE above this threshold consistently signifies that the authority is effectively managing the balance between supply and demand. Additionally, a year-long compliance standard allows for a comprehensive view of operational performance, which is valuable in assessing patterns and trends in grid reliability. Shorter timeframes, like weekly or monthly durations, would not provide the necessary data for substantiating long-term operational effectiveness or compliance with standards set forth by regulatory bodies.

Thus, the requirement to assess ACE against a backdrop of 12 months ensures that balancing authorities are not only managing immediate operational challenges but also adhering to ongoing compliance expectations over a significant period, thus promoting grid stability and reliability.