Critical Inertia

Minimum level of system inertia necessary to ensure deployment of frequency responsive reserves.

Definition in a NERC Webinar by ERCOT

Source: ¹ (p31)

The minimum level of system inertia necessary to ensure that frequency responsive reserves (both FFR and PFR) have sufficient time to be deployed and prevent the operation of the first stage of UFLS after the largest credible contingency.

Tip

Generally, the largest credible contingency is referred to as the Resource Loss Protection Criteria in BAL-003.

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Last modified: 2025-06-20

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1. NERC (2020). Industry Webinar- White Paper: Fast Frequency Response Concepts and Bulk Power System Reliability Needs. https://www.nerc.com/comm/PC/IRPTF_Webinars_DL/2020-04_Webinar-FFR_White_Paper.pdf ↩