"They Should Not Disconnect From the Grid": PJM's Account of the July 22 Load Transfer

PJM, the grid operator, published this account on its news site on August 11, 2026. It reports what PJM and Dominion discussed at the August 6 meeting of PJM's Operating Committee. The findings are called preliminary.

On the size of the event, its opening paragraph speaks of "a July 22 event that saw nearly 4,000 MW of data center load trip offline unexpectedly in Virginia. It was the largest such event in PJM history." The line under its headline, and a Dominion director further down, give about 3,800 MW.

At 7:56 a.m.

"According to Dominion's preliminary investigation, at 7:56 a.m. that Wednesday, a mechanical failure caused a 230 kV line to be automatically removed from service in Northern Virginia. As the fault was properly removed from the system, data centers in the Dominion zone unexpectedly disconnected from the grid. This caused spikes in voltage and system frequency."

The page then gives the sequence. On the word of a Dominion system operations director, "the first load drop of 2,970 MW took place when data centers started to transfer away, and system voltage increased."

The page goes on: "When these first Large Loads transferred to backup generation, the loss of their loads prompted high system voltage disturbances. In response, a second wave of 1,099 MW of data centers disconnected and transferred to on-site backup generation."

Within Nine Minutes

"PJM observed overall load drop from 99,984 MW to 96,205 MW. The PJM Control Center quickly dispatched generation down to balance the large change between generation and load, to restore system frequency to 60 Hz and to maintain grid stability."

"PJM recovered the Balancing Authority Area Control Error Limit within nine minutes, well within NERC standards of 30 minutes, and dispatched reactive power resources to lower system voltage."

The page's own summary: "The grid did not experience significant reliability impacts but did experience a high imbalance between generation and load and large swings in voltage and frequency."

A Normally Cleared Fault

The page quotes the chair of PJM's Operating Committee. "This was a normally cleared fault," the chair said. "They should not disconnect from the grid. These data centers are too sensitive to the kind of voltage that they like, and we feel they are disconnecting too early."

The page explains: "Computational loads on the grid, which include data centers, crypto mining facilities and others, set their protection system to monitor for sudden change or abnormal voltage levels and may rapidly switch to on-site backup generation in response to grid events, even during routine disturbances that are correctly cleared by transmission protection systems."

On earlier events: "Similar events in the Dominion zone caused sudden load transfers of about 1,500 MW each on Feb. 17, 2025, and July 10, 2024."

The First Phase

On the rules, the page says: "As it stands, computational loads are not subject to NERC Reliability Standards, and computational loads are not a NERC-registered entity."

It reports that FERC has ordered NERC to submit a first phase of new provisions by Dec. 31, 2026. A PJM reliability engineering manager is reported as saying that this first phase "will not address the minimum voltage or frequency ride-through requirements for computational loads." The page adds: "Those requirements are expected to be included in NERC Reliability Standards in 2027."

The page ends on a quotation from a PJM executive director, on why the work will go to the Planning Committee: "you really need these requirements in place before the load comes on the system."