Monitoring Grid Maintenance in ‘Shoulder Season’

Fall and spring bring the most work crews and cranes to the grid


As fall approaches, the days grow shorter, the nights grow cooler and milder temperatures prevail. That means less electricity demand on the grid. And that leaves opportunities to maintain or upgrade equipment and infrastructure for the bulk electric system that has served 65 million customers reliably throughout the heat of summer.

Between Sept. 16 and Dec. 31, PJM Interconnection and its members will operate during what we call a “shoulder season,” a term originally coined for the time between high- and low-demand seasons in the travel market. For PJM’s members, this happens twice a year, in autumn and spring, when lighter grid demand allows generators and transmission operators valuable time to temporarily disconnect and perform maintenance or make upgrades to their assets such as generators, transmission lines or substations.

From our Control Center in Valley Forge, PJM coordinates this crucial work. PJM reliability engineers and planning coordinators study proposed jobs and give the green light for when and how long facilities are deactivated so crews can get to work. They make sure they know if and when they can call equipment back to service for unexpected conditions, like a suddenly hot fall day or storm event.

As the regional transmission operator for 13 states and Washington, D.C., PJM manages transmission or adjusts generation as necessary to route power around thousands of maintenance jobs. This system work is crucial for PJM and our members so that the system is prepared to meet the rigors of peak demand days during the hottest summer days or coldest winter nights.

“Coordinating maintenance is one of the most important things that PJM does,” said Paul McGlynn, executive director – System Operations. “We need to let our operators build and maintain facilities so that the grid can be operated reliably throughout the peak season.”

Scheduling Work for Maximum Reliability

PJM coordinates all work on equipment tied to the bulk electric system, from a four-hour trip test on a substation breaker to the months-long construction timetable required to replace large transmission towers and lines.

For projects large and small, generators and transmission operators submit tickets to notify PJM well in advance, according to guidelines and timing dictated by Manual 3, “Transmission Operations.”  During these between-season periods, construction and repair work doubles, resulting in 6,000 separate maintenance jobs during the 2019 spring shoulder season alone.

The number of outage tickets increases between peak usage seasons.

Through daily communication, project analysis, monthly conference calls with transmission operators and more, PJM Reliability Engineering Manager Donnie Bielak’s team tracks job requests. This team charts how long a specific grid facility will be offline and, most importantly, whether the system can be operated reliably with the facility offline.

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

Fall shoulder season runs from Sept. 16 through year’s end. The late winter/spring shoulder season spans March 1 through June 14.

Special care is taken 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.

“Not all outages are created equal,” Bielak said, adding that planners must consider which outages have the most impact on the system. “Restoration time is something we consider when deciding whether to let a job proceed.”

Work Crews Most Active In October and April

Year round, PJM responds in real time to ensure seamless electricity delivery to customers. At any given time, an average of nearly 4 percent of generators may drop out of service temporarily for unforeseen events, like when generation equipment fails, breakers trip or storms disrupt service.

Managing the sheer volume of routine maintenance and capital improvements is a less glamorous but equally vital challenge quietly and consistently coordinated by PJM between its many members and neighboring regional transmission organizations. PJM’s manuals spell out the steps required for maintenance work on the grid to encompass lines, transformers, breakers, capacitors, reactors and all related equipment.

The maintenance activity peaks in October and April, with about 2,400 separate planned transmission outages during each of those two months and more than 50,000 MW of generator outages. That’s a significant chunk of PJM’s total generating capacity of about 180,000 MW.

Charting the Course of Grid Renewal

Some outages are also allowed in the summer and winter, though they are typically of shorter duration, with less of an impact to flows on the grid, and the equipment can be returned to service quickly if necessary. PJM will occasionally issue Hot or Cold Weather Alerts, which will request that generation and transmission owners suspend work and return their assets to service because those resources will be needed for higher loads driven by extreme weather.

PJM’s construction coordination challenge has mounted in recent years, with new projects required to maintain reliability, improve efficiency, interconnect new generators or replace aging equipment. Two-thirds of all system assets in PJM are more than 40 years old. “In shoulder season, everyone is trying to take advantage of milder weather to take care of what needs to be done,” said McGlynn. “Coordinating that work is a huge part of what we do.”