Large Load Interconnection Studies — LLIS / RTP / RPG end-to-end
Three-tier engineering-study sequence governs every large-load interconnection at PJM (Manual M-14H), MISO (BPM-015), ERCOT (§25.494), and CAISO. Tier 1 Feasibility (60-120 d, $50-200 K) — high-level yes/no + cost range. Tier 2 System Impact Study / SIS (6-12 mo, $0.5-2 M) — powerflow under multiple scenarios + N-1 contingencies, dynamic stability for 3φ-fault transients (PSS/E + IEEE Std 1110-2002 models), short-circuit (ASPEN/CAPE) vs breaker ratings, harmonic analysis to IEEE 519 (PSCAD/HARMFLO) when power-electronic loads present. Tier 3 Facilities Study (4-8 mo, $0.5-5 M) — final engineering + binding cost estimate + executed Interconnection Agreement. Cost allocation: direct assignment (100% applicant) vs network upgrade (DFAX) vs postage-stamp (rare). Affected Systems Studies coordinate cross-RTO impacts at major seams (PJM-MISO, MISO-SPP, SPP-WECC, CAISO-WECC); ERCOT exempt. FERC Order 1920 (2024) expands long-term transmission scenario planning. Compliance documents: ISA / LGIA / ERCOT IA + NERC TPL-001-5.1 (P0-P7 contingencies), PRC-024 (V/freq ride-through), PRC-025, IEEE 2800-2022 (IBR standard), MOD-026/027/032 (model data). Violation penalties up to $1 M / day. Total studies → executed agreement: 12-30 mo; construction adds 12-36 mo.
Step 1 - Three study tiers: Feasibility, SIS, Facilities Study
Reference notes
Every large-load interconnection — whether under PJM Manual M-14H, MISO BPM-015, ERCOT §25.494, or CAISO — passes through three progressively detailed engineering studies: Feasibility → System Impact Study (SIS) → Facilities Study. Total time from initial feasibility through executed Interconnection Agreement: 12-30 months. Construction adds another 12-36 months. Use Next → to walk through the three tiers, what each study computes, cost allocation, Affected Systems Studies, and the final compliance documents.
Three study tiers
| Tier | Duration | Cost ($) | Output |
|---|---|---|---|
| 1. Feasibility | 60-120 days | $50-200 K | Yes/no feasibility + rough cost range |
| 2. SIS | 6-12 months | $0.5-2 M | Required upgrades list + cost |
| 3. Facilities Study | 4-8 months | $0.5-5 M | Final design + signed Interconnection Agreement |
Regional naming: PJM — Feasibility / SIS / Facilities Study · MISO — same with BPM-015 procedures · ERCOT — Pre-screening / Impact Study / Facilities Study under §25.494.
What studies compute
- Powerflow: steady-state bus voltages + line flows under defined L/G patterns · PSS/E, Power World, TARA · checks: 0.95-1.05 pu voltages, MVA < thermal under N-1
- Dynamic stability: time-domain simulation of 3φ fault cleared 4-6 cycles · PSS/E + IEEE Std 1110-2002 turbine-gen models · checks: rotor angle stability, V recovery to 0.9 pu within 0.5 s
- Short-circuit analysis: fault-current contribution from every source · ASPEN OneLiner, CAPE · checks: breaker interrupting + momentary ratings, relay coordination
- Harmonic analysis (required for power-electronic loads): PSCAD electromagnetic + HARMFLO steady-state · IEEE 519 — typically 5 % V THD at PCC limit
- Hyperscale relevance: data-center UPS + SMPS create complex harmonic signatures · pre-emptive harmonic compliance avoids expensive retrofits
Network upgrades + cost allocation
- Direct assignment: upgrades exclusively serving applicant (new substation, tap line, dedicated transformer) — 100 % applicant cost
- Network upgrades: regional benefits — DFAX (Distribution Factor Analysis) allocation among contributing parties
- Postage-stamp: rare — broad system-reliability upgrades, allocated zonally across all loads
- Transmission Revenue Requirement (TRR): recovered through wholesale transmission rates (PJM/MISO/SPP)
- ERCOT: sponsoring TDSP fronts cost · direct + socialized split via TDSP tariff + transmission cost-of-service
- Hyperscale range: 200 MW data center can face $5M-$100M direct upgrade cost depending on local grid strength
Affected Systems Studies + FERC seams
- Trigger: material impact on neighboring RTO/BA → that neighbor performs Affected Systems Study
- Major seams: PJM-MISO (Eastern) · MISO-SPP · SPP-WECC · CAISO-WECC
- FERC framework: Order 1000 (coordinated regional planning) · Order 1920 (2024 — long-term scenario planning)
- ERCOT exception: isolated Texas Interconnection — no cross-RTO Affected Systems Studies (DC ties only)
- Seam delays: +6-12 months and tens of $M for neighbor-side upgrades
- Strategy: engage neighboring RTO during feasibility phase to avoid late-stage surprises
Compliance documents
- ISA (Interconnection Service Agreement) — at PJM, tri-party among load/LSE, transmission owner, PJM
- LGIA (Large Generator Interconnection Agreement) — generator-side equivalent · FERC Order 845 + 2023 pro forma
- ERCOT IA — governed by ERCOT Nodal Protocols + PUCT §25.494 · TDSP counterparty
- NERC TPL-001-5.1 — P0-P7 contingency categories every facility must withstand
- NERC PRC-024 — voltage + frequency ride-through requirements
- NERC PRC-025 — protection-system loadability
- IEEE 2800-2022 — IBR (inverter-based resource) standard; increasingly referenced for hyperscale loads with BESS/PV
- NERC MOD-026/027/032 — dynamic model data submission
- Compliance enforcement: registered-entity audits · penalties up to $1M / violation / day
Why it matters for the AWS Grid Code Compliance Manager role
The executed Interconnection Agreement is the foundation. Every operating decision a data center makes for the life of its assets must trace back to commitments in that agreement and the underlying NERC obligations. Annual compliance reviews verify ongoing conformance and identify modifications needed as equipment ages or operating patterns shift. The compliance manager owns this trace — from initial Feasibility filing through 20+ years of operation.