Best Practices for Large Load Interconnections: A North American Perspective on Data Centers

Overview

Large loads are expanding rapidly across North America, led by data centres, cryptocurrency mining, hydrogen production facilities and heavy-duty charging stations. Data centres draw particular attention as AI deployment drives unprecedented capacity growth; their scale, duty cycles and converter-dominated interfaces introduce new challenges for transmission interconnections regarding disturbance behaviour, steady-state performance and operational visibility. In July 2024 a 230 kV fault in the Eastern Interconnection tripped 1,500 MW of data-centre load; between late 2023 and early 2025 ERCOT and the Eastern Interconnection recorded 25 crypto-mining load losses of 100-400 MW each.

The authors extract explicit numeric limits at the point of interconnection and compare them. Large-load thresholds differ: Dominion ≥50 MW for power-electronic loads, ERCOT ≥75 MW per site with a 25 MW substation visibility threshold, Southern ≥50 MW above 40 kV, SPP >10 MW at 69 kV or >50 MW at higher voltage. Southern Company is the only entity in this review with a numeric ramp cap, ≤20 MW/min under normal operation. Power quality: Dominion ≤3% instantaneous voltage fluctuation at the POI; Ameren uses IEEE 519 and IEEE 1453; PG&E Rule 2 limits THD ≤5% and ~10% imbalance.

SPP's VRT curve is 0.90-1.10 pu continuous with short-duration tolerance down to ~0.50 pu for ~0.15 s; Dominion requires ride-through of several reclosing shots of ~50-70 ms with undervoltage pickup near 85%. SPP FRT example: continuous 58.8-61.2 Hz, extended tolerance for 299 s outside that band, trip permissible above ~61.8 Hz or below ~57.0 Hz. ERCOT is the only entity with a numeric recovery target: ≥90% of pre-disturbance load restored within 1 second once V_POI ≥ 0.9 pu (proposal). Only SPP and ERCOT publish explicit POI-based VRT envelopes; load FRT is mostly tied to UFLS schemes.

The finding is that protection and power-quality rules are fairly mature and converge on IEEE 519/1453, whereas ride-through envelopes, ramp limits, recovery targets and even the definition of a 'large load' vary widely; the authors argue for harmonised VRT/FRT envelopes and telemetry similar to European practice. Limits: a review of seven entities' published guidance; rules are evolving fast, and it is a preprint.

Key points

1. In July 2024 a 230 kV fault in the Eastern Interconnection tripped 1,500 MW of data-centre load; between late 2023 and early 2025 ERCOT and the Eastern Interconnection recorded 25 crypto-mining load losses of 100-400 MW each.
2. Large-load thresholds differ: Dominion ≥50 MW for power-electronic loads, ERCOT ≥75 MW per site (25 MW substation visibility threshold), Southern ≥50 MW above 40 kV, SPP >10 MW at 69 kV or >50 MW at higher voltage.
3. Southern Company is the only entity in this review with a numeric ramp cap: ≤20 MW/min under normal operation.
4. Power quality: Dominion ≤3% instantaneous voltage fluctuation at the POI; Ameren IEEE 519 and IEEE 1453; PG&E Rule 2 THD ≤5% and ~10% imbalance.
5. SPP's VRT curve: 0.90-1.10 pu continuous with short-duration tolerance down to ~0.50 pu for ~0.15 s; Dominion requires ride-through of several reclosing shots of ~50-70 ms with undervoltage pickup near 85%.
6. SPP FRT example: continuous 58.8-61.2 Hz, extended tolerance for 299 s outside that band, trip permissible above ~61.8 Hz or below ~57.0 Hz.
7. ERCOT is the only entity with a numeric recovery target: ≥90% of pre-disturbance load restored within 1 second once V_POI ≥ 0.9 pu (proposal).
8. Only SPP and ERCOT publish explicit POI-based VRT envelopes; load FRT is mostly tied to UFLS schemes.

Using it in design

• In a large-load interconnection application, verify the relevant entity's large-load threshold (10-75 MW) and ramp limit (Southern ≤20 MW/min) early; definitions differ widely between entities.
• Check data-centre ride-through design against the VRT envelopes at the point of connection (SPP: 0.90-1.10 pu continuous, ~0.50 pu for ~0.15 s; Dominion: several ~50-70 ms reclosing shots) and FRT bands.
• Design for power quality at the point of connection to IEEE 519 and IEEE 1453, and plan permanent power-quality metering and telemetry.
• Add the target ERCOT proposes for post-disturbance recovery (≥90% within 1 second) to UPS and load-reconnection logic.

Who should read it

Grid engineers and designers preparing large data-centre load interconnection applications and comparing entities' technical requirements.

Document contents

1. 1. Introduction
2. 2. USA Large Load Technical Interconnection Requirements
3. 3. European Experience and Vision
4. 4. Conclusion

Related standards

• IEEE 519
• IEEE 1453
• IEEE 2800-2022
• IEEE 1668-2017
• NERC PRC-029-1
• ITI (CBEMA) curve

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Publication details

Authors

Rafi Zahedi; Amin Zamani; Rahul Anilkumar

Publisher

CIGRE US National Committee, 2025 Grid of the Future Symposium (arXiv preprint)

Year

2025

Document number

arXiv:2601.12686

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.48550/arXiv.2601.12686

Licence

CC0 1.0 — public domain dedication; free to reuse

Licence evidence

arxiv.org

Citation