PJM initiated a load-shedding event Aug. 11 in the Baltimore Gas and Electric (BGE) region after the Brandon Shores substation went offline.

A PJM announcement states that the substation “experienced an unplanned disconnection” in the morning, after which transmission capability into the region was limited for much of the day and consumers were asked to conserve energy.

A voltage reduction action was initiated at 2:15 p.m. followed by a load-shed directive at 3:52 p.m. PJM’s emergency procedure page states that the directive was initiated due to an N-5 cascade risk identified on the Chestnut-Fredrick Road 115-kV line in BGE. The load-shed directive lasted 28 minutes, ending at 4:20, while the voltage reduction ended at 5:09.

“While BGE worked to address the transmission outage, electricity demand briefly exceeded the current capacity of the local transmission system as demand peaked in the afternoon. To prevent damage to equipment and the risk of cascading outages across a broader area, at 3:52 p.m. Eastern, PJM directed BGE to lower flows across overloaded lines by reducing electricity load. BGE concurred and implemented its load-reduction plan, resulting in limited outages,” PJM said in a notification to members.

Since the load shed was limited to BGE and did not extend to a full sub-zone, a performance assessment interval (PAI) was not initiated. PJM stated that some versions of its app incorrectly notified users of a PAI trigger.

BGE reported to PJM that transmission equipment that had been “inoperable” for much of the day had been brought back into service after the load-shed directive, allowing the action to be terminated. As of the 6:36 p.m. communication, some equipment still was offline.

“We expect that BGE will soon be returning to service those customers who were shed as part of our original directive. Continued reliable operation of the local transmission system will depend upon the operability of the transmission facilities that tripped this morning, but for now, the system is in a place such that we can serve our peak evening demand in the area,” PJM said.

The most recent load shed PJM had entered occurred on June 15, 2022, when storms damaged multiple transmission lines and put 200,000 customers along three 138-kV lines out of power. Following the December 2022 Winter Storm Elliott, PJM said it was one generation trip away from possibly having to implement a voltage reduction action. (See PJM Orders Load Sheds in AEP Following Storms and PJM Recounts Emergency Conditions, Actions in Elliott Report.)

Limited transmission capability in the Baltimore region contributed to the need for PJM to enter into a reliability-must-run (RMR) agreement with Talen Energy after it requested to deactivate its 1,289-MW Brandon Shores and the adjacent 843-MW H.A. Wagner generators.

Transmission violations identified with those units offline led to several transmission projects being added to the Regional Transmission Expansion Plan and a $180 million annual agreement to keep the two generators online.

The region also saw capacity prices surge above the rest of the RTO due to limited capability to import power from the rest of PJM. (See FERC Approves $180M Annually for RMR Deals with Brandon Shores and Wagner Plants and PJM Market Participants React to Spike in Capacity Prices.)