PJM Interconnection, North America’s largest Regional Transmission Operator (RTO), is mulling changes to interconnection reliability requirements for data centers and cryptocurrency mining facilities following a mass outage in Virginia late last month.

The outage occurred on July 22 and originated in northern Virginia, which is home to the highest concentration of data centers globally.

Reports at the time indicated that a transmission line went out of operation on the morning of the 22nd, prompting data centers in the area to disconnect their own systems from the grid and switch to backup power, according to Dominion Energy, the utility serving the region.

The outage brought nearly 4GW of data center capacity offline, and according to the RTO, it was the largest incident experienced across its footprint.

PJM said that during the outage, the grid did not experience significant reliability impacts but did experience a high imbalance between generation and load, seeing large swings in voltage and frequency.

Following the outage, PJM’s operating committee held a meeting with Dominion to discuss the preliminary findings from the event, system impacts, and work underway to develop standards to reliably integrate the operation of such computational loads on the bulk power system.

“This was a normally cleared fault,” PJM operating committee chair Emanuel Bernabeu 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.”

Bernabeu said that PJM and Dominion are continuing to jointly review the event and system impacts with an eye to stakeholder coordination for new standards.

“We are currently evaluating potential enhancements to reliability requirements, with consideration of existing and future industry ride-through standards and practices,” said Matthew Wharton, PJM manager, Reliability Engineering.

As data centers continue to proliferate, there is a risk that these outages become more commonplace. This is because data centers usually set their protection system to monitor for sudden changes or abnormal voltage levels and may rapidly switch to on-site backup generation in response to grid events. This can cause reliability issues for the grid by raising system frequency, causing an imbalance between generation and load, and increasing system voltage, which can damage physical grid infrastructure.

The Federal Energy Regulatory Commission has recognized these impacts, and in July it ordered the North American Electric Reliability Corporation to define and create the first phase of enforceable Reliability Standards needed to manage reliability risks posed by computational loads.