On July 22, 2026, a 230 kV line in Northern Virginia was automatically removed from service after a mechanical failure. The fault was properly removed from the system. Data centers in the Dominion zone then disconnected from the grid and transferred to backup generation. PJM called it the largest such event in its history. (PJM Inside Lines, August 11, 2026)
Update and correction
This article originally carried a headline that said no equipment failed. That contradicted PJM’s account. PJM, citing Dominion’s preliminary investigation, says a mechanical failure caused the 230 kV line to be removed from service at 7:56 a.m. (PJM Inside Lines, August 11, 2026)
The figures, as PJM states them
PJM says nearly 4,000 MW of data center load tripped offline. Brian Starling of Dominion Energy, quoted by PJM, gives a first load drop of 2,970 MW and a second wave of 1,099 MW. He puts the total at approximately 3,800 MW. (PJM Inside Lines, August 11, 2026)
PJM observed overall load fall from 99,984 MW to 96,205 MW. It dispatched generation down to restore system frequency to 60 Hz and dispatched reactive power resources to lower system voltage. It recovered its Balancing Authority Area Control Error limit within nine minutes. NERC standards allow 30 minutes. (PJM Inside Lines, August 11, 2026)
The grid did not see significant reliability impacts. It did see a large imbalance between generation and load, and large swings in voltage and frequency. (PJM Inside Lines, August 11, 2026)
How a cleared fault becomes a load loss
Dominion says the first transfers raised system voltage. The rise prompted the second wave to disconnect. (PJM Inside Lines, August 11, 2026)
Emanuel Bernabeu, chair of PJM’s Operating Committee, called it “a normally cleared fault.” He said the data centers “should not disconnect from the grid” and are “disconnecting too early.” (PJM Inside Lines, August 11, 2026)
The event was not the first. PJM reports similar transfers of about 1,500 MW each in the Dominion zone on July 10, 2024 and February 17, 2025. (PJM Inside Lines, August 11, 2026)
PJM describes the mechanism. Computational loads set their protection to watch for sudden change or abnormal voltage. They may switch rapidly to on-site generation, even for routine disturbances that transmission protection has cleared correctly. (PJM Inside Lines, August 11, 2026)
In Texas, ERCOT’s NOGRR282 has been in effect since August 1, 2026. It bars a large computational load from tripping or transferring solely because of a number of sags or swells in a period of time, where the load must ride through each one. If equipment limits force such a scheme, the load must be able to stay connected through at least six within 90 seconds. (ERCOT NOGRR282) (ERCOT NOGRR282, PUCT report)
Ride-through belongs to stored energy
A regulated power supply holds its output power, so its input current rises as voltage falls. (3DFS Data Centers and Compute) Nicholas Ingarra reports a test of an inverter under a constant-power load in which the current rose as its input voltage fell, and expects the higher current to add Joule heating. (In Compliance Magazine, 2026) An uninterruptible power supply carries a load through a sag, and a series sag corrector restores the missing voltage. (3DFS Resilience) Correction at the panel changes only one share of the drop: the share that the loads’ reactive, harmonic and unbalanced current makes across the plant’s own impedance. (3DFS Data Centers and Compute) A deep sag from the utility side stays with stored energy. (3DFS Resilience)
What comes next
FERC ordered NERC on July 16, 2026 to file computational load standards by December 31, 2026. (FERC order, Docket RD26-7-000) Matthew Wharton, PJM’s manager of reliability engineering, said that first phase will not address minimum voltage or frequency ride-through for computational loads. PJM reports that those requirements are expected in NERC standards in 2027. (PJM Inside Lines, August 11, 2026)
NERC’s Board of Trustees adopted the computational load standards on October 26, 2026. NERC will now file them with FERC. (NERC newsroom, October 27, 2026) The explanation is in NERC computational load standards explained.
Where this stands
PJM and Dominion continue their joint review. Their preliminary findings say the data centers disconnected after the fault was properly removed from the system. (PJM Inside Lines, August 11, 2026) A 3DFS panel controller does not ride through an interruption and does not hold the voltage the source delivers. (3DFS Data Centers and Compute) The first step for a site is one week of measurement at one power distribution unit.
Critical perspective
Transmission protection removed the fault properly on July 22, and the grid still lost about 3,800 MW (PJM Inside Lines, August 11, 2026). The decision to leave sat inside the facilities, whose protection watches for sudden change or abnormal voltage (PJM). No tariff rule stopped them. FERC’s June 18 order said it was “concerned that the Tariff does not specify ramp rate or ride-through requirements” (PJM Inside Lines, September 10, 2026).
PJM’s draft answers with numbers. It covers computational loads of 50 MW or more, with at least 25 MW behind power electronics, and sets voltage and frequency envelopes (PJM Planning Committee, October 6, 2026). It bars transfer schemes that act solely on a count of sags (PJM). It says shifting consumption to other resources does not by itself count as compliance (PJM).
The gaps matter as much. Sites already operating would have until January 16, 2028, or one year after commercial operation (PJM). PJM can cut that to 90 days for a site that contributes to a reliability criteria violation (PJM).
Working group recommendations that PJM presented note that all observed events involved facilities already in operation (PJM, October 6, 2026). The duty sits with the transmission customer serving the load, and each Transmission Owner may set stricter terms (PJM). PJM has not yet stated the consequence of failing to comply (PJM). FERC must still accept a filing that PJM targets for November (PJM).
The sites that tripped get the latest fixed deadline in the draft, unless PJM uses its 90-day power. An operator in Northern Virginia should treat January 2028 as a ceiling, not a plan. The sag-counting and undervoltage settings belong to the operator, and the audit can start now.
Frequently asked questions
Did equipment fail on July 22? Yes. PJM, citing Dominion, says a mechanical failure removed a 230 kV line from service. Protection removed the fault properly. The data centers then disconnected. (PJM Inside Lines, August 11, 2026)
How much load was lost? PJM says nearly 4,000 MW. Dominion reports waves of 2,970 MW and 1,099 MW and a total of approximately 3,800 MW. PJM load fell from 99,984 MW to 96,205 MW. (PJM Inside Lines, August 11, 2026)
Is there a national ride-through rule for data centers? Not yet. Computational loads are not subject to NERC Reliability Standards today, and the first NERC phase will not set minimum voltage or frequency ride-through. PJM reports that those requirements are expected in 2027. (PJM Inside Lines, August 11, 2026)
