What are the two categories of emergency outlined in NERC Standard EOP-011?

The two categories of emergency outlined in NERC Standard EOP-011 are Capacity and Energy. This distinction is important for ensuring that the electric grid remains stable during critical situations.

"Capacity" refers to the ability of the system to meet peak demand and the generation resources available during moments when electricity use is at its highest. In contrast, "Energy" pertains to the total amount of electricity available over a specific time period and relates to the generation’s ability to sustain supply during prolonged periods of high demand.

Understanding the difference between these two categories helps operators determine appropriate responses during emergencies, ensuring both short-term and long-term reliability. In an emergency, addressing capacity issues requires resources that can quickly be brought online, while energy considerations may focus on stored resources or generation that can provide sufficient output over time to restore balance to the grid.