Northern Virginia Data Center Disconnect Dumps 3 GW Off PJM Grid, Takes 10 Minutes to Stabilize

A transmission line fault in Ashburn, Virginia on July 22 caused more than 3 GW of data center load to disconnect from the PJM Interconnection grid simultaneously, removing roughly 3% of system demand and triggering a voltage disturbance that took 10 minutes to stabilize. PJM reported no formal reliability impacts, but residential customers in Northern Virginia experienced flickering lights and appliance disturbances. The incident, double the scale of a July 2024 event, has prompted PJM to pursue regulatory changes and NERC to develop mandatory modeling standards under a framework called PERC1.

Northern Virginia Data Center Disconnect Dumps 3 GW Off PJM Grid, Takes 10 Minutes to Stabilize - More than 3 GW of data center load disconnected from PJM simultaneously after a transmission line fault in Ashburn, Virginia on July 22 — roughly 3% of grid demand at the time 1 https://www.datacenterdynamics.com/en/news/pjm-grid-hit-by-voltage-disturbance-after-data-center-load-abruptly-drops-offline-report/ 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid - The grid took approximately 10 minutes to stabilize, versus the milliseconds typical for routine disturbances, with voltage anomalies detected from D.C. to Chicago 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 3 https://www.yahoo.com/news/science/articles/ai-data-centers-disconnecting-simultaneously-185616429.html - Dominion Energy confirmed data centers' own protection systems initiated the transfer to backup power — the utility did not disconnect them 4 https://www.datacenterknowledge.com/outages/fault-in-data-center-alley-triggered-3-gw-load-drop-on-pjm - The incident is roughly double the scale of a July 2024 event in which ~60 data centers dumped 1,500 MW, which prompted NERC to form a task force 3 https://www.yahoo.com/news/science/articles/ai-data-centers-disconnecting-simultaneously-185616429.html - PJM is pursuing regulatory changes to shift transmission and capacity costs onto data center developers, while NERC develops mandatory modeling standards under a framework called PERC1 3 https://www.yahoo.com/news/science/articles/ai-data-centers-disconnecting-simultaneously-185616429.html A transmission line fault in Ashburn, Virginia — the epicenter of the world's largest data center cluster — triggered a cascading grid event on July 22 that dumped more than 3 GW of load off the PJM Interconnection grid in seconds. Data centers' internal protection systems detected the fault and automatically transferred facilities to on-site backup generators, removing roughly 3% of PJM's total system demand almost simultaneously 1 https://www.datacenterdynamics.com/en/news/pjm-grid-hit-by-voltage-disturbance-after-data-center-load-abruptly-drops-offline-report/ 2 . The resulting voltage disturbance took approximately 10 minutes to resolve — orders of magnitude longer than the millisecond-scale corrections that grid operators typically execute for routine disturbances. Sensors operated by Ting Labs detected voltage anomalies across 1.4 million monitoring points stretching from Washington, D.C. to Chicago 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 3 . PJM Interconnection, the nation's largest regional transmission organization serving 67 million people across 13 states, reported no formal reliability impacts to the bulk power system. But residential customers in Northern Virginia reported flickering lights and audible disturbances from appliances during the event 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 3 . What Happened The fault originated on a transmission line serving the Ashburn area of Loudoun County, Virginia, home to 209 completed data centers with 43 more under construction — representing over 53 million square feet of capacity and no comparable market concentration anywhere in the world 4 . When the transmission line went out of service Wednesday morning, data centers' automated protection systems detected the grid fault and initiated transfer to on-site backup generators. The simultaneous disconnection of dozens of facilities created a sudden demand vacuum on the PJM system 1 https://www.datacenterdynamics.com/en/news/pjm-grid-hit-by-voltage-disturbance-after-data-center-load-abruptly-drops-offline-report/ 4 . Dominion Energy spokesperson Jeremy Slayton confirmed that 'no load was shed and Dominion Energy did not disconnect area data centers from the grid; the data centers' own control systems transferred them to backup power' 4 . Grid Impact and Stabilization The abrupt disappearance of 3 GW created what grid engineers describe as an oversupply condition: generators were still producing power that no longer had a destination, causing voltage spikes and frequency wobbles across the interconnection 3 . Bob Marshall, CEO of grid-monitoring firm Ting Labs, said his company's 1.4 million sensors registered widespread power quality degradation. 'The power quality took a pretty big hit,' Marshall said 3 . PJM registered a measurable frequency shift — the electrical equivalent of a cardiac arrhythmia — but stated that grid reliability was maintained throughout the event. Normal operating conditions were restored within minutes, though full stabilization took approximately 10 minutes 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 4 . Precedent: The July 2024 Incident The July 22 event is roughly double the scale of a similar incident in July 2024, when approximately 60 Virginia data centers disconnected simultaneously and dumped roughly 1,500 MW onto the grid. That event forced emergency action to avoid cascading outages and prompted the North American Electric Reliability Corporation NERC to form a dedicated task force 3 . NERC warned at the time that 'the grid is not designed to withstand the loss of 1,500 MW data centers. At some level it becomes too large to withstand unless more grid resources are added' 3 . The July 22 event also came less than three weeks after PJM issued its first-ever 'Emergency Use of Backup-Generator Warning' during a regional heat wave, underscoring the growing strain that concentrated data center load places on grid operations 4 . Regulatory Response NERC is developing mandatory modeling standards under a technical framework called PERC1, which would require high-resolution monitoring to give grid operators better visibility into large load concentrations before future disconnection events 3 . PJM is separately pursuing regulatory changes to shift transmission and capacity costs onto data center developers rather than spreading them across all ratepayers — a significant policy shift that would alter the economics of siting new facilities in the PJM footprint 3 . At the state level, Texas and Pennsylvania are weighing frameworks that would allow utilities to curtail large commercial loads before residential customers during grid emergencies. The NRDC and bipartisan legislators have also proposed requiring data centers to supply their own power capacity rather than relying on public grid resources 3 . Outlook PJM projects adding 5 to 7 GW of annual data center demand through 2032 but estimates only 2 to 3 GW of new supply will come online over the same period, creating a widening gap that risks reliability shortfalls as early as June 2027 3 . The July 22 incident demonstrates that the grid risk from data centers is not solely about total power consumption but about the instantaneous load dynamics of concentrated facilities. When multiple gigawatts of demand vanish in seconds, the resulting oversupply can destabilize transmission systems across thousands of miles — a risk profile that has no historical precedent in U.S. grid operations 2 https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 3 . Companies mentioned Further sources 1 Data Center Dynamics - PJM grid hit by voltage disturbance after data center lo… ↗ https://www.datacenterdynamics.com/en/news/pjm-grid-hit-by-voltage-disturbance-after-data-center-load-abruptly-drops-offline-report/ 2 Reuters via US News - Massive disconnect of power roils largest US electric grid ↗ https://www.usnews.com/news/us/articles/2026-07-22/massive-disconnect-of-power-roiled-largest-us-electric-grid 3 Yahoo News - How AI Data Centers Disconnecting Simultaneously Caused a 1,000-Mi… ↗ https://www.yahoo.com/news/science/articles/ai-data-centers-disconnecting-simultaneously-185616429.html 4 Data Center Knowledge - Fault in Data Center Alley Triggered 3 GW Load Drop on … ↗ https://www.datacenterknowledge.com/outages/fault-in-data-center-alley-triggered-3-gw-load-drop-on-pjm The stories that matter, in one email. Free — unsubscribe anytime.