Comparative Analysis of Large Load Interconnection Requirements Across U.S. Transmission Entities

Overview

The rapid growth of large loads, especially AI-driven data centres, is creating unprecedented demands on the North American electric grid. Data centres account for nearly 80% of large-load interconnection requests in the Western Interconnection, and DOE projects U.S. data-centre use of 325-580 TWh by 2028. Despite this, technical interconnection requirements for large loads have not yet matured and contain gaps. The paper compares eleven entities across seven technical categories: large-load definition, load data and modelling, fault ride-through, load curtailment and shedding, dispatchability, power quality and reactive power control.

The lowest large-load threshold is 10 MW (SPP, loads at 69 kV); LIPA uses 20 MW and 50 MW is the most common threshold. ERCOT's proposed VRT: continuous 0.90-1.10 pu, current during disturbances not above 150% of normal maximum for no more than 0.5 s, and return to at least 90% of pre-disturbance consumption within 2 s after voltage exceeds 0.90 pu. SPP requires staying connected through at least six fault-clearing attempts within 90 s and prohibits constant-power control during disturbances; Dominion requires riding through at least six reclosing attempts of 50-70 ms. CAISO requires up to 6.0 s ride-through in the 0.70-0.90 pu band, roughly 3× the 2.0 s required by ERCOT, SPP, MISO and LIPA; all five numeric envelopes permit tripping above 1.20 pu.

Ramp-rate limits: Southern 20 MW/min, Duke 10 MW/min, MISO 30 MW/min (plus 10 MW max change in a sliding 5 s window), SPP 20 MW/min, LIPA 20 MW/min, CAISO 20 MW/min. Southern Company FFT oscillation limit: 10 MW max per 0.1 Hz bin for 0.1-5 Hz and 2.5 MW for 5-55 Hz; LIPA caps any two adjacent bins at 10 MW and all bins at 20 MW in 0.1-5 Hz, and 3.5 MW in 5-55 Hz. MISO's proposal requires withstanding three voltage disturbances within 10 s and phase-angle jumps up to 25 degrees.

The maturity assessment finds LIPA covering all categories and Dominion/Duke close behind, while dispatchability and oscillation limits remain inconsistent. The authors argue that on-site generators and BESS let hyperscale sites act as grid resources rather than only loads. Limits: rules are evolving quickly and measurement methods differ between entities; it is a preprint.

Key points

1. Data centres make up nearly 80% of large-load interconnection requests in the Western Interconnection; DOE projects U.S. data-centre use of 325-580 TWh by 2028.
2. The lowest large-load threshold is 10 MW (SPP, loads at 69 kV); LIPA uses 20 MW and 50 MW is the most common threshold.
3. ERCOT's proposed VRT: continuous 0.90-1.10 pu, current during disturbances not above 150% of normal maximum for no more than 0.5 s, and return to at least 90% of pre-disturbance consumption within 2 s after voltage exceeds 0.90 pu.
4. SPP requires staying connected through at least six fault-clearing attempts within 90 s and prohibits constant-power control during disturbances; Dominion requires riding through at least six reclosing attempts of 50-70 ms.
5. CAISO requires up to 6.0 s ride-through in the 0.70-0.90 pu band, roughly 3× the 2.0 s required by ERCOT, SPP, MISO and LIPA; all five numeric envelopes permit tripping above 1.20 pu.
6. Ramp-rate limits: Southern 20 MW/min, Duke 10 MW/min, MISO 30 MW/min (plus 10 MW max change in a sliding 5 s window), SPP 20 MW/min, LIPA 20 MW/min, CAISO 20 MW/min.
7. Southern Company FFT oscillation limit: 10 MW max per 0.1 Hz bin for 0.1-5 Hz and 2.5 MW for 5-55 Hz; LIPA caps any two adjacent bins at 10 MW and all bins at 20 MW in 0.1-5 Hz, and 3.5 MW in 5-55 Hz.
8. MISO's proposal requires withstanding three voltage disturbances within 10 s and phase-angle jumps up to 25 degrees.

Using it in design

• Design data-centre UPS and load control to the most restrictive entity's requirement: 6.0 s ride-through at 0.70-0.90 pu (CAISO), six fault-clearing attempts within 90 s (SPP), six 50-70 ms reclosings (Dominion), and the ban on constant-power control (SPP).
• Make ramp limits (10-30 MW/min) and FFT oscillation limits (Southern: 10 MW per bin at 0.1-5 Hz, 2.5 MW at 5-55 Hz) inputs to the load profile and storage sizing.
• Add the post-disturbance recovery target (ERCOT proposal: at least 90% within 2 s) to UPS and load-reconnection logic.
• Verify the large-load definition (10-50 MW thresholds) early in application scoping.

Who should read it

Grid engineers and designers preparing large data-centre load interconnection across several U.S. entities.

Document contents

1. 1. Introduction
2. 2. Comparative Findings of U.S. Transmission Entities (2.1 Large load definition, 2.2 Load data and modeling, 2.3 Fault ride-through, 2.4 Load curtailment and load shedding, 2.5 Dispatchability, 2.6 Power quality, 2.7 Reactive power control)
3. 3. Conclusion

Related standards

• IEEE 2800-2022
• NERC PRC-029-1
• ITI (CBEMA) curve
• IEEE 519
• IEEE 1453

Read the document

Publication details

Authors

Rafi Zahedi; Rahul Anilkumar; Amin Zamani

Publisher

CIGRE US National Committee, 2026 Grid of the Future Symposium (arXiv preprint)

Year

2026

Document number

arXiv:2610.36645

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.48550/arXiv.2610.36645

Licence

CC0 1.0 — public domain dedication; free to reuse

Licence evidence

arxiv.org

Citation