PJM proposes ride-through rules for data centers after 3,800 MW drop-off

PJM Interconnection has proposed adding voltage and frequency ride-through requirements for large computational loads, a category that includes data centers and crypto-mining facilities per PJM's description, in a presentation its generator modeling staff gave the Planning Committee on September 8, 2026. The proposal would require these loads to stay connected through the voltage and frequency excursions that follow normally cleared transmission faults, and PJM's own write-up of the meeting says it plans to file proposed solutions at FERC in November. The trigger was a July 22, 2026 fault on a single 230 kV line in the Dominion zone after which, according to the deck PJM presented to its Operating Committee on August 6, approximately 3,800 MW of load transferred to backup power; Dominion's preliminary findings in the same deck identify it as data center load in the Loudoun and Prince William load pockets in northern Virginia.

Under the deck's proposed voltage envelope, a load consumes power at its pre-disturbance level inside the continuous operating range; in the sags below it, the load may reduce consumption in proportion to the voltage drop, or as needed in the deepest zone, but shall return to more than 90% of its pre-disturbance level within 2 seconds after voltage returns to between 0.9 and 1.1 per unit. Cooling load is allowed to trip when voltage falls below 0.35 per unit, and overcurrent during a sag shall not exceed 150% of the facility's maximum current consumption during normal operations. On frequency, the deck sets a continuous operating range of 58.8 to 61.2 Hz in which loads maintain pre-disturbance power, and says a load "should continue to consume active power within 10% of the pre-disturbance level during frequency deviations requiring ride-through."

The requirements would apply to existing and future large loads, and PJM's write-up says Byoungkon Choi, the principal engineer in its generator modeling group, told stakeholders that staff intends to work with existing facilities on a transition plan. "PJM plans to establish these requirements as soon as possible," Choi said. The deck's timeline runs from an education session on September 15 and a second review of manual and tariff language on October 6 to the November filing, with ramp-rate requirements in the first quarter of 2027 and a full design envelope for stakeholder endorsement by the third quarter of 2027.

The August 6 deck, presented by PJM's reliability engineering manager, carries Dominion's preliminary findings. At 7:56 a.m., a single sub-conductor of a double bundle pulled free from its compression sleeve; the apparent cause was improperly torqued bolts. Protection cleared the fault in two to three cycles, and during the line's reclosing attempts data center load in the Loudoun and Prince William load pockets transferred away from the grid: an initial loss of 2,970 MW at 7:56:33 and, after the resulting high voltage, a second loss of 1,099 MW at 7:57:40. Those two event-log entries sum to 4,069 MW; the findings' separate load-transfer approximation, the difference between readings of 17,448 MW at 7:56 and 13,579 MW at 7:57, is 3,869 MW. The findings record the load back on the grid within 30 minutes, and one data center back-fed the fault three times.

PJM's event review gives the system-wide numbers: load fell from 99,984 MW to 96,205 MW, and PJM recovered its area control error limit within nine minutes against a NERC standard of 30. It was the largest such transfer in PJM's history, after events of about 1,500 MW each on July 10, 2024 and February 17, 2025. "This was a normally cleared fault," Operating Committee chair Emanuel Bernabeu said, per the review. "They should not disconnect from the grid." On September 8, David Souder, PJM's executive director for system operations, called it the third separate measurable event in two years and, per PJM's write-up, "unsustainable."

The transfer PJM now wants to prevent is one it has twice asked to be able to order. PJM's account of the May heat event says it obtained Department of Energy orders under section 202(c) of the Federal Power Act in January and on May 17 letting it direct transmission owners, as a last resort before load shed, to curtail data centers and other large loads that have backup generation; neither was used. The difference in July was who threw the switch.

Where the rules come from

FERC's June 18, 2026 order in docket EL26-67-000 opened a section 206 proceeding on how PJM's tariff handles transmission service for large loads. Among its concerns, the Commission wrote that "the Tariff does not specify ramp rate or ride-through requirements with which the transmission customer taking transmission service on behalf of the large load must comply." On August 14, FERC held the proceeding in abeyance for 90 days at the request of PJM and its transmission owners, moving responses to November 16, 2026; PJM told the Commission it intends to make section 205 filings by early to mid-November after an advisory stakeholder vote at the October 28 Members Committee, and a filing made by November 16 suspends the filer's obligation to respond. Separately, per PJM's event review, FERC on July 16 ordered NERC to file a first phase of enforceable standards for computational loads by December 31, 2026, and PJM's Matthew Wharton said, per the review, that phase will not cover minimum ride-through, expected in NERC standards in 2027.

PJM is not first. Its deck compares the proposal with ERCOT's PUCT-approved envelope, MISO's draft, and terms Dominion and AEP already impose. ERCOT's requirements, in the deck's summary of them, do not apply to loads that meet certain conditions, for example those operational or approved to energize on or before November 14, 2025, or with an interconnection agreement signed before that date with a transmission service provider or, if co-located, a generation resource; the deck refers readers to NOGRR282 for the full exemption conditions. MISO's draft asks for return to more than 90% within 1 second where PJM's proposal allows 2.

Ride-through is also the standard at the center of Oklo's August complaint against PJM, in which the company says PJM applied a low-voltage ride-through test meant for inverter-based resources to its whole 750 MW project. Inverter-based generators, mostly wind and solar, have had PJM's voluntary ride-through guidelines since 2019, per the event review; the load side is getting its first.

Outlook

The transition plan for existing facilities is where the proposal's reach will be decided. PJM's deck reproduces ERCOT's example exemptions, including loads operating or approved before November 14, 2025, without saying whether it will copy them; the deck gives no energization dates for the load that tripped on July 22, so how much of it a cutoff like ERCOT's would leave outside the new envelope, and dependent on the transition plan Choi described, is not knowable from the cited documents. The deck puts the full design envelope in 2027, about when NERC's ride-through standard is expected, so the November filing will likely carry the minimum envelope and leave the detail to the stakeholder process.