As inverter-based resources (IBRs) continue to reshape the Bulk Power System, the industry’s ability to accurately model, verify, and validate generation behavior has become a reliability imperative—not just a planning exercise. The technical rationale behind NERC Reliability Standard MOD-026-2 makes one thing clear: legacy modeling approaches are no longer sufficient for today’s grid.
MOD-026-2 represents a significant evolution from MOD-026-1 and MOD-027-1, consolidating and modernizing requirements to better reflect how generators, IBRs, flexible alternating current transmission systems (FACTS), synchronous condensers, and HVDC facilities actually perform under real-world conditions. At its core, the standard is about confidence—confidence that the models used in planning studies accurately represent in-service equipment and can be relied upon during both normal operations and large system disturbances. 
Why the Change?
The driver for MOD-026-2 is well documented. Industry reviews, disturbance reports, and FERC Order No. 901 all point to the same conclusion: inadequate modeling of IBR controls, protections, and large-signal behavior has contributed to unexpected tripping and reduced system resilience. Events like the Odessa disturbances demonstrated that traditional positive-sequence models alone cannot fully capture inverter behavior during unbalanced faults, weak-grid conditions, or fast control interactions.
Clear Roles, Clear Expectations
MOD-026-2 formalizes coordination across functional entities. Generator Owners and Transmission Owners are responsible for providing verified and validated models that reflect actual field settings. Transmission Planners and Planning Coordinators must clearly define model requirements—positive sequence and EMT—and apply transparent, documented acceptance criteria.
Positive Sequence and EMT
MOD-026-2 formally integrates electromagnetic transient (EMT) modeling for IBRs, FACTS, and HVDC facilities where appropriate. EMT models are essential for understanding large-signal behavior, unbalanced faults, control interactions, and inverter protection responses that cannot be represented with sufficient fidelity in RMS simulations. EMT models become the benchmark for validating positive-sequence models, ensuring planning tools remain credible as IBR penetration increases.
Lifecycle Model Management
MOD-026-2 reinforces that model accuracy is not a one-time obligation. Verification and validation periodicity requirements recognize that equipment changes, control updates, and plant modifications can materially affect dynamic performance. The 10-year maximum validation cycle—shorter when changes occur—promotes continuous model quality management rather than reactive compliance.
From Compliance to Reliability Value
Better models lead to better decisions. Accurate representation of generator and IBR behavior enables planners to identify instability risks earlier, assess mitigation options more effectively, and avoid surprises during real disturbances.
For Generator Owners, Transmission Owners, and planners alike, MOD-026-2 is not just another compliance checkbox. It signals that modeling is now a frontline reliability function.