Access historical data for each instance since 1999 in which ISO New England has had to implement ISO Operating Procedure No. 4: Action During a Capacity Deficiency (OP 4). The reports cover which OP 4 actions were taken, a brief summary of the reasons for the actions, when they were implemented, and when they were canceled.
ISO New England implements this procedure when available resources are insufficient to meet anticipated electricity demand plus required operating reserves. The procedure includes 11 steps that the operators can take to either increase the available supply of electricity for the region or reduce the actual real-time demand for electricity. These steps can be implemented in any order depending on the circumstances of the capacity deficiency. In addition, some of the steps can be implemented in advance of an anticipated capacity deficiency situation. OP 4 can be implemented New England-wide, by local control center area, by state, or targeted to specific area. The potential New England load relief resulting from implementing all 11 steps of OP 4 is about 2,000–4,500 megawatts (MW) and is dependent on factors such as circumstances surrounding the appeals, including timing and the amount of advanced notice that can be given.
It is important to note that OP 4 is an implicit part of the reliability design of the power grid in New England. It was envisioned that instances would occur when required operating reserves could not be maintained and that appropriate contingency measures needed to be in place.