A heat wave that moved through the Northeast US coincided with transmission outages on Long Island to result in significant power price volatility, with real-time power prices bouncing from minus $3,800/MWh to over $1,500/MWh Aug. 11 and 12.
The local utility provider called on customers to cut power usage Aug. 13 as extreme heat continued to stress the power grid.
During a period of "sustained extreme heat and humidity and the successive failures of third-party owned supply systems," Public Service Enterprise Group Long Island is "now urging all customers on Long Island and in the Rockaways to reduce electric use as much as possible during the peak hours of 3 pm and 7 pm Aug. 13," the Long Island Power Authority said in a statement.
Peak power demand is "at risk of exceeding the available energy supply" and reductions in customer energy use are also required to reduce demand, LIPA said.
The New York Independent System Operator also activated Special Case Resources and Emergency Demand Response Program resources in Zone K Long Island 1-8 pm Aug. 13.
"The Y49 cable, which is owned by the New York Power Authority, came out of service Aug. 6," Jen Hayen, a spokeswoman with LIPA, said in an Aug. 13 email. "NYPA and PSEG Long Island (our service provider) are investigating the specifics of the failure."
The Y50 cable, jointly owned by LIPA and Consolidated Edison, came out of service in July because of a fault in Westchester County, New York, she said, adding Con Ed expects a return-to-service date around mid-September.
This loss of about 900 MW of net import capability from the outages of the Y49 and Y50 cables is in addition to the outage at NYPA's 150-MW Flynn dual-fuel power plant and a partial outage of the Neptune cable resulting from a failed transformer which is affecting about 300 MW of capability, Hayen said.
Neptune is a 65-mile undersea and underground high voltage direct current transmission line that extends from Sayreville, New Jersey to Nassau County on Long Island. The line's capacity is 660 MW, but it only delivered about 375 MW Aug. 12, NYISO data said.
Further compounding supply outages, the NYISO issued thunderstorm alerts late afternoon Aug. 12, during which there is a need to rely more on local capacity in case a transmission line is struck by lightning.
These operational changes resulted in some power pricing volatility, with real-time prices in NYISO Zone G briefly going into negative territory while Zone K Long Island real-time prices were above $1,200/MWh.
Temperatures were above 90 degrees Fahrenheit on Long Island around 3 pm Aug. 13 and the National Weather Service had issued a Heat Advisory for the region until 8 pm.
NYISO Zone K real-time power prices briefly jumped above $1,200/MWh around that time before falling back to $242/MWh, which remained above the rest of the state where real-time prices were around $50/MWh.
"An aging, non-flexible generation fleet and transmission constraints are some of the main challenges on Long Island," Peter Cavan, director of market development at developer Convergent Energy + Power, said in a phone call.
He called the week's extreme weather, along with power delivery and supply constraints that led to the pricing volatility, "an unfortunate combination of events."
NYISO power demand peaked at just under 30,000 MW Aug. 12, slightly below forecast. The Aug. 13 peak load forecast was slightly lower than the day before.
The NYISO's peak load forecast for Aug. 16 is 22,823 MW, which should relieve some stress on the grid.