A fault on a 230-kilovolt transmission line in Dominion Energy’s service territory triggered the largest single load-loss event in PJM’s recorded history this July. The regional grid operator shed 3.8 gigawatts of demand in two waves, pulling total system load from roughly 100,000 megawatts down to 96,205 megawatts \u2014 a 3.8 percent drop.<\/p>\n
Dispatchers contained the imbalance in nine minutes, well inside the 30-minute window set by the North American Electric Reliability Corporation, but only after emergency dispatch of reactive power resources to steady frequency and voltage.<\/p>\n
The episode exposed a structural problem concentrated in northern Virginia, the world’s densest cluster of data centers. Although the fault itself was cleared through normal procedures, data center equipment disconnected en masse anyway. PJM’s operating committee found that facility protection settings are calibrated to react to even minor voltage deviations \u2014 causing computational loads to drop offline far sooner than the situation required.<\/p>\n
The pattern is not new. Comparable abrupt load swings of up to 1.5 GW had already been recorded in Dominion’s zone during 2024 and 2025. PJM is now weighing expanded reliability requirements, including ride-through standards that would require facilities to stay connected through transient disturbances.<\/p>\n
Regulatory action remains months away at best. NERC will not finalize minimum voltage and frequency ride-through rules before next year. On a separate but related track, NERC is developing registration criteria and baseline reliability standards for attaching large computational loads \u2014 data centers and cryptocurrency mining operations \u2014 to bulk transmission infrastructure, with a December 31 target for final criteria.<\/p>\n
PJM executive director of system operations David Souder put the urgency plainly: “These requirements really need to be in place before the load shows up in the system.”<\/p>\n