[AI](/news/ai/)
[AI](/news/tag/ai/)
[AI INFRASTRUCTURE](/news/tag/ai-infrastructure/)
[DATA CENTERS](/news/tag/data-centers/)
[DOMINION ENERGY](/news/tag/dominion-energy/)
[GRID RELIABILITY](/news/tag/grid-reliability/)
[NORTHERN VIRGINIA](/news/tag/northern-virginia/)
[PJM](/news/tag/pjm/)
[POWER](/news/tag/power/)
[RIDE-THROUGH](/news/tag/ride-through/)
- Nearly 3,800 MW of Northern Virginia computational load transferred from PJM to onsite generation on July 22, the largest such event in PJM history. [1] - The event followed the automatic removal of a 230 kV transmission line after a mechanical failure; PJM said the fault was properly cleared. [1] - PJM restored its area control error within nine minutes and used generation reductions and reactive-power resources to manage voltage and frequency swings. [1] - PJM and Dominion Energy are evaluating ride-through requirements and other reliability enhancements for existing and future large loads. [1] - FERC directed NERC on July 16 to develop enforceable reliability standards for computational loads, with the first phase due by December 31, 2026.
[2] PJM Interconnection is evaluating new reliability requirements for data centers and other computational loads after nearly 3,800 MW of Northern Virginia demand transferred to onsite generation during a July 22 transmission disturbance. The event was the largest sudden large-load transfer in PJM’s history, according to the grid operator. [1]
The event began at 7:56 a.m. when a mechanical failure automatically removed a 230-kilovolt transmission line in Northern Virginia. After the fault was cleared, data centers in Dominion Energy’s zone transferred away from the grid in two waves. PJM said the first transfer involved approximately 2,970 MW, followed by another 1,099 MW as system voltage increased; it reported approximately 3,800 MW of large load disconnected and transferred in total. [1]
PJM said the grid experienced a high imbalance between generation and load, along with substantial voltage and frequency swings, but no significant reliability impact. Operators reduced generation, dispatched reactive-power resources and recovered the balancing-authority-area control error within nine minutes, compared with a 30-minute NERC requirement. [1]
The July 22 Event #
Dominion Energy told PJM that the transmission-line failure was a normally cleared system fault, not a utility-directed load-shedding action. Data center protection systems transferred facilities to backup generation in response to the disturbance. [1]
PJM’s observed system load fell from 99,984 MW to 96,205 MW. The operator reduced generation to rebalance supply and demand, restore frequency to 60 hertz and limit the effect of the transfer on the bulk system. [1]
PJM’s Reliability Review #
PJM and Dominion are jointly reviewing the event and its system impacts, with the work moving through PJM’s stakeholder process and Planning Committee. PJM Manager of Reliability Engineering Matthew Wharton said the review will consider existing and future industry ride-through standards and practices. [1]
Potential requirements could address voltage and frequency ride-through, protection coordination, dynamic load models, event telemetry, disturbance reporting, onsite-generation transfer behavior and coordinated reconnection. The aim is to prevent a normal transmission fault from triggering a larger system disturbance through simultaneous customer action. [3]
PJM’s review includes existing and future large loads, although PJM officials said technical requirements need to be established before new facilities enter service. [1]
Federal Standards Are Moving Separately #
The PJM review follows a July 16 order from the Federal Energy Regulatory Commission directing the North American Electric Reliability Corporation to develop reliability standards for computational loads connected to the bulk power system. FERC cited the unprecedented growth of data center demand as a reason for requiring a more certain standards-development process. [2]
PJM said the first phase of NERC’s work is due by December 31, 2026, but is not expected to establish minimum voltage- or frequency-ride-through requirements for computational loads. Those requirements are expected in a later phase of NERC standards work in 2027. [1]
NERC’s May 2026 Level 3 alert required registered entities to address computational-load modeling, studies, instrumentation, commissioning, operations, protection and control. [4]
A Repeated Northern Virginia Pattern #
The July event followed two earlier Northern Virginia incidents that each produced approximately 1,500 MW of sudden load transfers, in July 2024 and February 2025. The latest event was more than twice the size of either prior incident. [1]
NERC’s earlier incident review found that a transmission fault in the Eastern Interconnection caused roughly 1,500 MW of data center-type load to transfer to backup systems, producing frequency and voltage increases. The review identified the differing behavior of uninterruptible-power-supply systems and protection controls as a planning and operating challenge. [5]
For PJM, the reliability question is shifting from the size of a data center’s normal electricity demand to the facility’s behavior during a disturbance, including how much load remains grid-dependent, how quickly it transfers behind the meter and how it reconnects. [3]
Companies mentioned #
Further sources #
[[1] PJM, Dominion Review Large Load Transfer Event, PJM Inside Lines, August 11, 20… ↗](https://insidelines.pjm.com/pjm-dominion-review-large-load-transfer-event/)
[[2] FERC Order RD26-7-000 directing NERC to develop reliability standards for compu… ↗](https://www.ferc.gov/media/e-1-rd26-7-000)
[[3] 3.8 GW Load Drop Prompts Potential PJM Data Center Rules, Data Center Knowledge… ↗](https://www.datacenterknowledge.com/regulations/3-8-gw-load-drop-prompts-potential-pjm-rules)
[[4] NERC Large Loads Action Plan, including the May 4, 2026 Level 3 Computational L… ↗](https://prod.nerc.com/initiatives/large-loads-action-plan)
[[5] NERC Incident Review: Considering Simultaneous Voltage-Sensitive Load Reduction… ↗](https://www.nerc.com/pa/rrm/ea/Documents/Incident_Review_Large_Load_Loss.pdf)
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