Region’s supply of electricity was insufficient to meet consumer demand
System operators implemented well established procedures Christmas Eve to maintain New England’s power supply during an unanticipated electric capacity deficiency, according to a report from ISO New England.
The operator blamed unexpected generator outages and reductions, and power providers who failed to meet their contractual obligations, for the shortfall, which started with an Abnormal Conditions alert being issued at 4 p.m. The capacity deficiency ended at 7 p.m.
Underperformance by contracted resources is penalized at a rate of $3,500 per megawatt-hour, the report says, and may result in assessments of approximately $39 million being charged to providers who failed to meet their supply obligations during the Christmas Eve event.
ISO New England controls the bulk power system and transmission lines in Connecticut, Massachusetts, Maine, New Hampshire, Rhode Island and Vermont. The report “December 24, 2022 OP-4 Event and Capacity Scarcity Condition” was prepared by its Executive Vice President and Chief Operation Officer, Vamsi Chadalavada, and released Jan. 5.
According to the report, the capacity deficiency was declared when approximately 2,150 megawatts of scheduled power resources became unavailable at the same time as approximately 1,100 megawatts of net power imports were below expectations.
A capacity deficiency means the region’s supply of electricity is insufficient to meet consumer demand along with required operating reserves, the report says. In a news release, the ISO noted that this differs from energy emergencies, which typically occur when a significant amount of resources lack the fuel to produce electricity over an extended period that can last until fuel supplies are replenished.
That morning, the ISO had forecast a peak load demand of 17,510 megawatts. The load actually peaked at 17,524 megawatts.
In its release about the event, the ISO noted that electric grid operators across North America faced significant supply challenges Christmas Eve resulting in widespread outages to distribution systems. The situation was particularly severe in North and South Carolina, where Duke Energy had to initiate rolling blackouts that affected about 500,000 customers and, in some case, last hours.
For ISO New England, the situation resulted in the unusual condition of it being more economical to use oil-fired generation, rather than gas, which typically provides most of the region’s electricity.
Many dual-fuel generators switched to burn fuel oil, the report says, with approximately 29 percent of the region’s energy demand being met by oil-fired generation.
Prices in the Real-Time Energy Market averaged approximately $484 per megawatt-hour over the course of the day, the report says, with averages reaching $2,200 per megawatt-hour during the 5 p.m. hour.
By comparison, at 5 p.m. Monday, ISO New England showed market prices of approximately $82.50 per megawatt-hour, with no oil-fired generation.
Under its 11-step table of actions for responding to a capacity deficiency, known as Operating Procedure No. 4, ISO New England reached Action 4 – Power Watch. At this stage, it asks for voluntary load curtailment from market participants and is authorized to make a public appeal to conserve electricity.
The ISO said that because of the short duration of the event, it did not call for public conservation.
A summary of the day’s events in the report notes that temperatures across New England were colder than forecast due to an arctic air mass that moved further east than projected. At 5 p.m. Dec. 24 the temperature was 15 degrees in Hartford, according to the weather site CustomWeather.
Throughout the day, and continuing after the power deficiency occurred, generators experienced outages or reductions, causing ISO New England to commit all available remaining offline resources to come online.
“Causes of generator outages and reductions varied; some reported cold weather-related outages or reductions,” the report states.
The report concludes saying 21-day energy supplies remain adequate and the recent cold weather did not result in a significant depletion of regional liquefied natural gas inventories.