ISO-NE successfully manages through July 5 capacity deficiency
ISO New England system operators utilized actions from a well-established operating procedure to balance supply and demand on the regional power system during a capacity deficiency in the evening peak hours of July 5, 2023.
Shortly after 6 p.m., a transmission equipment failure significantly reduced imported electricity coming to New England. At the same time, consumer demand for electricity was slightly higher than expected. This combination left the region short of the resources required to meet consumer demand and required operating reserves.
To mitigate this situation, system operators implemented Actions 1 and 2 under Operating Procedure No. 4, or OP-4, utilizing a portion of the region’s operating reserves and declaring an Energy Emergency Alert (EEA) Level 1, the lowest of three alert levels.
The capacity deficiency was mitigated within 30 minutes, and the region remained in OP-4 for 3.5 hours as peak demand receded and the power system returned to normal operations. To prevent going in and out of OP-4, operators can remain in the procedure until they are confident the issues on the system have been resolved.
An issue with the data that feeds ISO New England’s website and mobile app caused these platforms to report erroneously that system conditions were abnormal for several hours after the event. In reality, system conditions returned to normal at 10 p.m. on July 5.
The transmission outage occurring in the midst of the evening peak meant that sufficient resources were not able to respond quickly enough to avoid the capacity deficiency. Resources have different operating characteristics that affect the time it takes for them to start up.
ISO New England did not issue appeals for public conservation during this event; consumer conservation wasn’t necessary given the short duration of the event and the ability of reserve resources to make up the deficiency.
In and of themselves, capacity deficiencies are not always emergencies. They simply mean that ISO operators are taking additional actions to maintain system reliability. More information on capacity deficiencies, and how the ISO manages through them, is available on the ISO New England website.
ISO New England will provide more detailed information as it becomes available.