PJM has created a new emergency procedure and is testing a software fix following poor generator response to a minimum generation event July 5, officials told the Operating Committee last week.
Extremely mild temperatures and a holiday weekend resulted in an RTO peak of 61,300 MW — unusually light but in line with PJM’s forecast — forcing PJM officials to curtail 2,000 MW of imports and order cuts of 100% of reducible generation.
Of about 200 generation owners, only 31 (16%) responded to the eDart minimum generation report. Of those that responded, only half reported an emergency reducible value greater than 0 MW.
But only 1,458 MW of the 1,665 MW of reducibles — units that said they were willing to go below their economic minimum — responded, PJM’s Chris Pilong told the committee.
Among combined-cycle owners that responded, all reported economic minimum ratings — the lowest level a unit can achieve while following economic dispatch — equal to their emergency minimum — the minimum generation that can be produced by a unit while maintaining stability.
“We only know what the generation operators, owners tell us,” said Mike Bryson, executive director of system operations.
Pilong said the responses indicate the need for additional training. “We really need to be sure we have the right rules in place so that people are reporting the real emergency min and not the eco min.”
Low Prices
Pilong said many generators entered low-priced offers for the weekend, wanting to keep running over the holiday to capitalize on hot weather forecast for the following week. Pilong said operators also were stressed by the inability of PJM’s dispatch engine to set proper price signals for wind units bidding below $0/MWh.
The RTO is testing a software fix to allow prices as low as -$60/MWh, which should help incent wind units to respond automatically via automatic generation control (AGC). Currently, some wind operators do not respond to AGC signals, requiring phone calls from PJM operators.
In addition, PJM has created a new minimum generation advisory procedure that it can issue one or two days in advance of anticipated light load days.
Minimum Generation Event Chronology
PJM declared a minimum generation alert at 10:25 p.m. July 4, saying the RTO was within 3,286 MW of normal minimum energy limits.
At 12:25 a.m. July 5, a Saturday, operators issued a minimum generation emergency declaration, reducing prices to $0/MWh and indicating a need to cut generation at 3 a.m.
Shortly before 3 a.m., operators declared a minimum generation event, ordering a 50% cut in reducible generation. Generators were encouraged to sell energy outside the control area.
Thirty-five minutes later, operators upped the call for reducible generation cuts to 100%. It remained there until shortly before 8 a.m., when it was reduced to 50%.
Before then, at 3:30 a.m., operators manually ordered all remaining wind (1,000 MW) to zero and ordered three other generators offline. All hydro was either offline or pumping into storage.
Hot Water Heaters
John Farber of the Delaware Public Service Commission said the incident illustrated why PJM should create a resource category for thermal storage, such as hot water heaters, that can provide load. “PJM could help [the Department of Energy] move off the dime,” Farber said.
Farber was referring to DOE’s pending decision on whether to exempt large capacity grid-interactive water heaters from current energy efficiency standards or regulate them under a separate category.
