Under which category do the NERC “FAC” standards fall?

The NERC "FAC" standards, which focus on facility ratings, deal specifically with the standards needed to ensure that the elements of the power system, such as transmission lines and substations, are rated appropriately to handle expected operating conditions and load scenarios. These standards establish the requirements for determining the thermal, voltage, and stability ratings of transmission facilities, ensuring that they can operate reliably and safely under specified conditions.

The emphasis of these standards is on maintaining the integrity and reliability of the bulk electric system by ensuring that facilities are correctly rated to support operational needs. This involves not only evaluating the physical and electrical characteristics of the facilities but also ensuring compliance with these ratings during normal and abnormal operating conditions.

In the context of the other categories, transmission planning and operations encompass a broader scope of system operation and management, generator performance and compliance focus on individual generating units, and environmental impact assessments are centered on the environmental effects of energy generation and transmission. Therefore, the "FAC" standards are specifically aligned with the performance and rating of facilities, reinforcing why this category is the correct choice.