What is the timeframe for a system operator to restore contingency reserve after recovery?

The correct timeframe for a system operator to restore contingency reserve after recovery is 90 minutes. This timeframe is critical in ensuring that the transmission system remains stable and capable of responding to any subsequent contingencies.

Contingency reserves are designed to provide backup power in the event of unexpected outages or loss of generation. The 90-minute requirement emphasizes the importance of prompt restoration, allowing system operators to maintain enough reserves to respond to potential disturbances or emergencies effectively. This is in line with reliability standards set by regulatory bodies, which aim to ensure that electric systems can withstand and quickly recover from unexpected failures.

Other options, while they represent shorter or longer timeframes, do not align with the established guidelines that require a thorough and timely restoration of reserves. Thus, understanding the 90-minute restoration timeframe is essential for effective transmission operations and maintaining system reliability.