NERC MOD-026 Small-Signal Stability Assessment Template

Small-signal stability refers to a power system’s ability to maintain synchronism under small, gradual disturbances—typically modeled using linearized differential-algebraic equations around an operating point. MOD-026 requires transmission planners and owners to perform eigenvalue-based modal analysis to identify low-damped or unstable oscillatory modes, especially those sensitive to inverter-based resources (IBRs), high-voltage direct current (HVDC) links, and reduced system inertia. The Excel template structures inputs (system topology, model types, operating conditions), analysis parameters (mode selection criteria, participation factors, damping sensitivity studies), and outputs (eigenvalues, damping ratios, mode shapes, contingency summaries) to ensure traceability and auditability. It mandates documentation of modeling assumptions—including generator excitation systems, power system stabilizers (PSS), IBR control dynamics (e.g., grid-forming vs. grid-following), and network representation fidelity—to support regulatory review. Compliance involves submitting completed templates to Regional Entities and the ERO for validation, with non-compliance triggering remediation plans or reliability assessments.