PJM Studying Grid Performance During Challenging Autumn Heat


Generators, transmission operators and load management resources successfully worked with PJM operators to maintain reliability during a short, abnormal October heat wave that led to emergency procedures, a Performance Assessment Interval and the first call on demand-response resources in more than five years.

Rebecca Carroll, director – Dispatch.

An early operations analysis of grid performance also showed operations and potential forecasting and visibility challenges, and these are undergoing further study as the data becomes available, said Rebecca Carroll, director – Dispatch, in presentations last week (Oct. 16–17) to PJM’s Operating Committee and Market Implementation Committee.

Unusual temperatures into the 90s on Oct. 1 across much of PJM’s footprint resulted in peak demand that exceeded the load forecast by about 5,500 MW and peaked at over 125,500 MW.

The hot weather took place during the peak of fall shoulder season, which is when critical, planned maintenance activities take generators out of service and significantly trim the approximately 180,000 MW of total generating capacity in the PJM footprint.

As demand ramped upward at around 2 p.m. on Oct. 1, PJM called on spinning reserves for about 15 minutes, and imported an estimated 800 MW of power from the Northeast Power Coordinating Council region, which includes New York, New England and eastern Canada. Rising demand also incurred three intervals of shortage pricing, Carroll added.

Managing Through System Vulnerabilities for a Second Hot Fall Day

PJM used the experience of Oct. 1 to revise the forecast for Oct. 2, with record high temperatures expected in almost all areas except Illinois. Facing a peak of more than 131,000 MW on Oct. 2, on the evening of Oct. 1, PJM called a Maximum Generation Emergency/Load Management Alert, which provides an early alert that system conditions may require the use of the PJM emergency procedures.

On the morning of Oct. 2, a 765 kV line was automatically taken out of service to isolate failed equipment. Later in the morning, PJM was notified that as much as 2,000 MW of generation that was expected to be available would not be on-line for the peak of the day.

“We started to have concerns about being able to meet that peak load we were forecasting,” Carroll said. With congestion mounting on constrained facilities like the Peach Bottom-Conastone 500-kV line along the Pennsylvania-Maryland border, and the loss of generation that we were expecting to be available for the peak, PJM operators were concerned about capacity issues heading into the peak hours of the day.

At noon, PJM issued a Pre-Emergency Load Management Reduction Action to address capacity concerns over the peak. This would ease expected congestion impacted by load and generation in the territory covered by Dominion, Pepco, Baltimore Gas & Electric and AEP, with a request for load relief to begin at 2 p.m., and anticipated to continue through the peak.

A Pre-Emergency Load Management Reduction Action yields load relief using PJM-controllable load management programs. These include voluntary commercial, industrial and residential programs in which customers receive compensation for agreeing to shave electricity consumption. Once load relief is requested, that resource has to be offline for a minimum of one hour, Carroll said.

PJM’s early analysis shows an estimated 725 MW of demand response load relief from the Pre-Emergency Load Reduction Action called by PJM. Final demand response figures will be available in early December, Carroll said.

Performance Assessment Interval Study Underway

The Pre-Emergency Load Management Reduction Action also triggered a Performance Assessment Interval, or PAI, in which capacity resources in the affected zones are required to perform. It was PJM’s first PAI that will affect generation resources.

A PAI measures how well the generation resources that were committed to PJM to perform actually delivered when called upon. The PAI tool, a component of PJM’s Capacity Performance rules, helps ensure that energy is ready when it is needed most, particularly during extreme heat or cold.

Under Capacity Performance, resources that fail to meet their commitment during emergencies are assessed a penalty. Resources that exceed their obligation, and those that perform during an emergency despite having no capacity obligation, are entitled to receive some of the funds collected from underperforming units.

PJM has called for a PAI twice previously, but each event involved very small areas related to localized transmission issues, and no demand response was called, so no generation or load management resources were impacted.

“We are determining all of the generator performance that occurred during the Performance Assessment Interval in those four zones,” Carroll said, adding that a paper focusing on the operational decisions and pricing outcomes will be presented at the November Operating Committee meeting.

Market Conditions Scrutiny

Some stakeholders expressed concerns about market volatility, with prices spiking when energy demand ramped up steeply Oct. 1, and plunging during demand response activities Oct. 2. Carroll replied that PJM adhered to procedures and best practices to ensure grid reliability. Other stakeholders pointed out contributions from demand response.

According to PJM’s Tariff, a PAI is automatically triggered whenever a Pre-Emergency Load Management Reduction Action is called.

“We felt pretty comfortable calling [the load management procedures] because of the tripping of the 765 kV line, the units that had failed to start, and the way the anticipated congestion was going to bottle generation in the east.”

Actual Load Lower Than Expected

While PJM undertook emergency actions to assure reliable grid operations with cooperation by stakeholders, the Oct. 2 actual peak reached only 126,500 MW, significantly lower than the projected 131,000 MW forecast.

As a result, the call for the PAI ended by 3:45 p.m. in the Dominion, Pepco and BG&E zones, and 4 p.m. in the AEP zone.

The quick response of load-reducing resources, coupled with a cold front moving through Illinois and northeast Ohio, only partially explains how demand drastically slowed its climb in the afternoon. PJM is conducting a detailed analysis, or “backcasting,” to account for why total load that day came in only 1,000 MW higher than the day before, despite much higher overall temperatures.

 “We are trying to figure out what happened that day, and why the load did not materialize the way we anticipated,” she said of PJM’s query into missing load totaling some 3,000 MW. “Is there a lack of visibility into something that came into play?”

One variable PJM faced is how much relief the call for demand response would actually deliver.

“Since we were outside of the compliance period for some of the demand response resources that were called, we could potentially see as little as 15 percent of what we had requested,” she said. “The door was open to see if we would need to call more.”

Stakeholders can expect more details at the November Operating Committee meeting. Among issues to be addressed are how temperature and load progression informed decisions, stakeholders’ questions on pricing, information about demand response, and more.

Final demand response numbers will be available in early January, with the first month’s statements detailing non-performing charges or credits to be expected in February 2020.

A brief Q&A document about the event is available now.