PJM cut loads in Indiana, Michigan, Ohio and Pennsylvania Tuesday as 90-degree temperatures pushed loads to the highest ever for September, stressing the grid at a time when much generation and transmission was offline due to planned outages.
Load peaked at 144,370 MW Tuesday and would have been higher Wednesday but for demand response. PJM said it tapped almost 6,000 MW of demand response resources Wednesday –- an all time record, equivalent to five nuclear plants –- limiting the day’s demand to 142,071 MW.
Demand for the two days was higher than any day this summer except July 18, when load hit 157,509 MW. (See Focus on AEP Transformer, Prices in Heat Wave Review; Imports, Not DR, Caused Heat Wave Price Crash.)
Last year, September loads never exceeded 130,000 MW.
Tuesday’s peak load was almost 3% above the RTO’s 140,500 MW forecast. “We under-forecast by quite a bit,” Adam Keech, director of wholesale market operations, told the Market Implementation Committee in a briefing Wednesday.
The large change in temperatures from Monday to Tuesday made load forecasting more difficult, officials explained yesterday. “We look closely at the patterns of the previous day’s temperatures and load when forecasting for a day, and, when they greatly differ, it’s much more difficult to estimate the day’s load,” said PJM spokesman Ray Dotter.
In response to a question from the Michigan Public Service Commission at the MIC meeting, PJM officials acknowledged they had ordered Indiana Michigan Power to shed load. But they provided members no specifics and did not mention that the RTO had cut loads in four states.
That disclosure came when PJM issued a press release later Wednesday, in which it said that the “unusual, extreme heat combined with local equipment problems to create emergency conditions in Indiana, Michigan, Ohio and Pennsylvania. “
The RTO said it was forced to cut load in those areas “to avoid the possibility of an uncontrolled blackout over a larger area that would have affected many more people.”
“We sincerely regret that conditions on the grid yesterday required us to call for emergency reductions in consumer demand,” the release quoted PJM CEO Terry Boston.
The initial statement provided no details on the location, size or duration of the cuts. PJM told RTO Insider Thursday the cuts totaled about 150 MW and ranged from one to eight hours: the Erie South substation, in Penelec, was off for about 6 hours; the Tod substation, in FirstEnergy’s ATSI zone, about 1.5 hours; the Summit substation, in AEP’s Indiana Michigan Power, 1 hour and I&M’s Pigeon River substation, about 8 hours.
According to local media reports, Indiana Michigan Power (I&M) reported more than 3,300 customers in Northwest Fort Wayne lost power at 7:15 p.m. Tuesday, with power was restored by 8:30 p.m.
I&M also cut power to about 1,072 customers in White Pigeon, Michigan, beginning about 1 p.m. Tuesday. All customers were returned to service by 9 p.m.
Wednesday, PJM called on emergency demand response but did not issue any additional load shed orders.
PJM issued a hot weather alert in the west beginning Monday. On Tuesday, it deployed emergency demand response in ATSI from 15:50 to 21:30. Keech said DR set marginal prices at $1,800/MWh “for the better part of peak.”
PJM also had an unusually long spin event — about one hour — because of difficulty maintaining its Area Control Error (ACE). “We under-forecast load… we had to make it up somewhere,” Keech explained.
The Northeast Power Coordinating Council (NPCC) responded to a call for shared reserves with 800 MW.
Keech said the Cleveland interface was a major challenge with multiple transmission lines tripping.
Wednesday brought a maximum generation alert for the entire RTO, with PJM activating emergency DR in both the AEP and ATSI zones. Keech noted that forecasts called for thunderstorms that had the potential of quickly dampening load.
“If the storms come in during the peak we potentially get stuck holding the bag for emergency DR,“ Keech said.
Officials did not provide members any details about the amount of transmission and generation out of service for maintenance. However, the Nuclear Regulatory Commission reported that four nuclear plants in or near PJM – Exelon’s Peach Bottom 3 and Braidwood 1; Dominion’s North Anna 1, Detroit Edison’s Fermi 2 — were out of service today.