Author: Aabid Sheikh
The November 19, 2025 SPP GIAG meeting focused heavily on strengthening the region’s interconnection and modeling framework as the system transitions toward high penetrations of inverter-based resources (IBRs). SPP outlined new technical requirements for plant-level dynamic models, expanded expectations for IBR verification and testing, and clarified parallel processes (HILLGA) governing large-load assessments and surplus capacity requests. Alongside these policy updates, SPP also provided a detailed status review of ongoing GI studies, highlighting an increasingly complex schedule of restudies, model freezes, and deliverability analyses that will shape development timelines heading into 2026. Below is a brief summary of the meeting’s key points and discussions.
Inverter Based Resource Framework
SPP is advancing a comprehensive framework for Inverter Based Resource (IBR) modeling requirements to support planning and operational reliability as IBRs increase across the system. The proposal focuses on detailed plant level dynamic modelling during the interconnection study phase, supported by unit-level type testing and OEM model validation, as well as plant-level model development, design and as-built evaluations, commissioning tests, post-commissioning validations, verification of testable features, and disturbance-based model validation.
To meet regulatory and reliability objectives, SPP proposes that interconnection customers submit a full modelling package at the time of request which includes:
- PSS/E standard library model
- PSS/E user defined model
- TSAT standard library
- TSAT user defined model
- PSCAD user defined model
The models should be consistent with FERC Order 2023 mandates, NERC FAC-002 revisions, and IEEE 2800-2022 expectations.
The framework establishes strict requirements for model usability, topology accuracy, and organized file packaging across modeling environments. It also outlines an extensive dynamic testing regime addressing initialization, voltage and frequency disturbances, balanced fault ride-through, high- and low-voltage ride through, frequency ride-through capabilities, protection performance and short-circuit ratio sensitivity to ensure models faithfully replicate real-world behavior.
Development of these requirements is led by the technical working group with support from RTWG, MWG, MDAG, and ORWG, and stakeholders are encouraged to submit comments by December 5, 2025, as SPP continues to refine a modeling framework intended to enhance consistency, accuracy, and system reliability in an evolving grid dominated by IBRs.
HILLGA and Surplus Priority Processing
Moreover, SPP procedures for High Impact Large Load Generator Assessment (HILLGA) and Surplus Priority Processing outline two complementary frameworks governing major interconnection requests and incremental capacity increases within the generation interconnection process. HILLGA, established under FERC Docket ER26-247 and implemented through Attachment BB Business Practice 7250, requires a HILL Delivery Point Study Agreement and extensive submission materials.
HILLGA Rules
To submit a HILLGA request, applicants must provide several required items through the Request Management System (RMS) to GI Special Studies. These include an executed HILLGA Study Agreement and special contract, which must be completed prior to FERC acceptance, along with a nonrefundable application fee of $20,000. In addition, a study deposit is required which includes $250,000 for projects up to 500 MW and $500,000 for those exceeding 500 MW. Applicants must also demonstrate site control as part of the submission package.
The submission requirements also include providing a detailed POI, Name plate capacity, Maximum injection capacity and Network resource deliverability. The HILLGA system impact study includes steady state, short-circuit, stability, and EMT screening analyses and identifies necessary network upgrades, with SPP delivering the SIS report and a draft HILLGIA within 90 days of the review period and allowing 45 days for negotiation.
Surplus Priority Processing
In parallel, Surplus Priority Processing—governed by filings ER25-3570, ER26-153, and ER26-156, offers an expedited, limited-duration pathway (sunsetting at the Commercial Pricing Point in March 2026) for existing generating facilities to request up to a 20% increase in Maximum Injection Capability. These requests require a PSIS Agreement, a $10,000 application fee, a deposit equal to 150% of standard study amounts, $8,000/MW in financial security, site control or equivalent security, and evidence of project readiness such as equipment orders, permits, and full financing, along with a COD within five years. The single-phase PSIS includes all typical DISIS Phase 1 and 2 analyses plus EMT screening and must be completed within 90 days, followed by a 15-day Priority Decision Point.
Surplus Priority requests receive queue priority and are studied for ERIS, with optional NRIS elections depending on upgrade availability.
Together, these processes require substantial financial commitments and technical documentation while ensuring robust system impact evaluation, EMT screening, and reliability protections, enabling SPP to manage both large new interconnections and incremental expansions in a transparent, timely, and reliability-focused manner.
Looking Ahead
The Generation Interconnection (GI) Status Update outlines an extensive set of ongoing and upcoming SPP interconnection studies, highlighting a tightly coordinated schedule spanning late 2025 through early 2026 for major efforts such as ERAS-2025, the DISIS-2023-001 Restudy, and DISIS-2024-001 Phase 1. The update provides draft and final report postings, model freezes, study starts, and review windows. It also maps out broader multi-year GI workflow activities from Phase 2 and Facility Analyses to Deliverability Projects (DP2), restudies, Final Studies (FS), and GIA negotiation periods across multiple clusters with overlapping timelines.
In parallel, numerous special surplus, modification, replacement, and sensitivity studies remain active, many operating on defined 30-, 43-, 60-, or 180-day schedules, with several surplus studies showing varied progress percentages and due dates contingent on updated customer model submissions. The report emphasizes the dynamic nature of the study schedule, driven by customer inputs, consultant reviews, and queued request withdrawals, and notes procedural elements such as cure windows, model freeze periods, and publicly accessible schedules.
Overall, the update underscores that SPP is managing a substantial portfolio of interconnection and special studies concurrently, each with defined milestones critical to supporting long-term system planning and generator integration, while providing clear points of contact for DISIS, AFS, and special-study inquiries to facilitate stakeholder coordination.
Access more on SPP, here.
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