PJM lost 3 GW in seconds. Ashburn is now a siting risk

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.