Spring Means ‘Shoulder Season’ in PJM

Scheduling Equipment Outages for Needed Repairs Requires Coordination


The first day of spring on March 19 falls in the middle of “shoulder season” for PJM and other grid operators. Now is the time when milder temperatures and lower electricity use enable transmission and generator owners to take equipment offline to perform necessary grid maintenance, repairs and upgrades.

Shoulder season happens twice a year in PJM, between more energy-intensive winter and summer peak seasons. During the coldest and hottest weather, routine grid outages are restricted to maximize the generation and transmission available for higher electricity demand, or load. The first shoulder season of 2024 runs from Feb. 29 through June 10. Overall, April, May and October tend to be the busiest times for shoulder season outages and associated grid upgrades.

As the regional transmission operator for 13 states and Washington, D.C., PJM is responsible for coordinating maintenance performed by its member transmission and generation owners while maintaining the reliable flow of power.

During the winter and summer peak season, PJM coordinates with transmission and generation owners to keep as much equipment in service and available as possible. On average during the peak winter and summer days, PJM approves 30 transmission jobs daily. During fall and winter this number increases exponentially to approximately 200 jobs a day. Most of the major transmission jobs start at the beginning of the week.

Among generation resources, PJM averaged about 28,000 MW worth of daily outages in spring 2023 with highs reaching over 50,000 MW in outages on any given day, which is more than 25% of total system capacity. The daily average generation outage last fall was about 33,000 MW.

PJM reliability engineers and planning coordinators study proposed outages in order to give the green light for when and how long facilities may be deactivated so crews can get to work. PJM engineers make sure they know if and when they can call transmission or generation equipment back to service to keep the lights on during unexpected conditions, like a suddenly hot or cold spring or fall day or storm event.

PJM manages transmission or adjusts generation as necessary to route power around maintenance jobs. Coordination of this system work is crucial for PJM and our members, preparing the system to meet the rigors of peak demand during the hottest summer days or coldest winter nights.

For projects large and small, generators and transmission operators submit job tickets to notify PJM well in advance, according to guidelines and timing dictated by Manual 3, “Transmission Operations.”  PJM’s reliability engineers then chart how long a specific grid facility will be offline and, most importantly, whether the system can still be operated reliably.

Any transmission outages exceeding five days are scheduled, wherever possible, six months to one year in advance. Shorter jobs should request PJM’s go-ahead at least one month prior.

PJM takes special care during the beginning and ending days of any shoulder season, when unusually hot or cold climate conditions or storms are most likely to spark a sudden demand for power.

Should PJM forecast such a spike in electricity demand due to unseasonable extreme heat/cold, PJM may issue a maintenance outage recall. When PJM calls generation facilities back to meet system requirements, generation owners have 72 hours to restore those assets to service. This happened during hot temperatures over the Memorial Day weekend in 2022.

Some outages are also allowed to take place in peak seasons, summer or winter, as needed. These maintenance jobs are typically shorter, with less system impact, and the equipment being worked on can be quickly returned to service if necessary.