How is EMS data exchange conducted between PJM and members?

The correct answer is that EMS data exchange between PJM and its members is conducted by exception, and upon demand. This method allows for real-time data sharing and responsiveness to specific situations that may arise in the operations of the electrical grid. It ensures that members receive up-to-date information as needed rather than adhering to a regular schedule. This flexibility is crucial for maintaining the reliability and efficiency of the transmission system, as conditions can change rapidly and require immediate attention.

The other options suggest timing or frequency constraints that don't align with the operational needs of a transmission organization. For instance, limiting exchanges to scheduled maintenance periods would mean that critical information could be delayed, potentially leading to issues in grid management and reliability. Monthly or annual updates would also be inadequate for the dynamic and sometimes immediate requirement for data in managing electrical transmission systems effectively. By using a model that allows for exception-based communication, PJM can ensure that its members are promptly informed and can act on important data without unnecessary delays.