PJM lost 3 GW in seconds. Ashburn is now a siting risk
The physics arrived before the rulebook. Both are now priced into where a campus can go.
A single transmission line fault in Ashburn, Virginia, pulled more than 3 GW of data center load off the PJM grid in seconds on the morning of Wednesday, July 22. Nothing burned and nobody lost service. The campuses’ own control systems read the disturbance and transferred them to backup generation, which is exactly what they were built to do and exactly what a grid operator does not want them to do. PJM said the event produced “a measurable frequency change but no reliability impacts to the bulk power system.” Dominion Energy said its protections worked as intended.
Why it matters
That is the problem, not the reassurance. A generator of that size is required to ride through a normally cleared fault. A large load, today, is not, so 3 percent of the largest grid in the country can vote itself off the system on a fault it was never in danger from. Regulators will close that gap, and the closing mechanism is the interconnection agreement.
PJM’s Board floated the shape of it in January 2026, months before Ashburn made the case: new large loads either bring their own new generation or accept a connect and manage framework with earlier curtailment. Read that as a menu. Speed of energization is now something a developer buys with flexibility, and the price is set per site.
The numbers
More than 3 GW, roughly 3 percent of PJM demand at that moment, gone between 7:55 and 8 a.m. The voltage disturbance registered from Washington to Chicago and took about 10 minutes to settle. NERC’s May 2026 Level 3 Essential Action alert already directed entities to study and implement fixes that avoid nonconsequential loss of firm computational load from normally cleared faults. Responses to its 33 questions are due August 3, 2026, twelve days after the event that proved the point. FERC has ordered NERC to file mandatory reliability standards for computational loads by December 31, 2026.
What’s next
Underwrite ride-through as a capital item, not a utility footnote: EMT models of your UPS behavior, dynamic fault recording, commissioning tests before full load, and a curtailment provision you can actually operate against. Ask the interconnecting utility what it will require, in writing, before the land closes. The densest load pockets now carry the heaviest conditions, which is a real argument for secondary metros. More national coverage.
On the record
What we checked ourselves, and where you can check it too.
- Public recordPJM's Board had already proposed the remedy six months before the event. Its January 16, 2026 plan offers new large loads a choice between bringing their own new generation and taking a connect and manage framework subject to earlier curtailment, read directly from PJM's own announcement rather than from coverage of it.View the record on insidelines.pjm.com
- Our coverageThis is the reliability half of the PJM data center fight we covered on the cost side four days earlier, when five state advocates told FERC it was failing to keep data center transmission costs off household bills. Same load pocket, second gate.Read our earlier story →
Sources
- Data Center KnowledgeFault in Data Center Alley Triggered 3 GW Load Drop on PJM
- RTO InsiderLine Fault Causes 3 GW in Data Center Load to Drop in Virginia
- PJM Inside LinesPJM Board Outlines Plans To Integrate Large Loads Reliably
- Morgan LewisNERC Alert Moves Data Centers From Emerging Risks to Planning Obligations
- POWER MagazineFERC Orders Mandatory NERC Reliability Standards for Data Center and Other Computational Loads