2009 Scenario Reliability Assessment - NERC

Scenario Reliability Self-Assessmentsobserve the actual way in which they have or would eventually operate, and as such, a historicalperspective is unavailable for both modeling and planning purposes.Table New England-1 provides a comparison between the Reference Case and the Scenario Casefor the various types of NERC Reserve Margins for the summer 2018 target assessment year.Table New England -1 – Comparison of 2018 Summer Margins:Reference versus Scenario Case2018 Summer Margins: ReferenceCase (%)Region/Sub-Region Target Capacity Margin N/A N/ARegion/Sub-Region Target Reserve Margin N/A N/AExisting Certain and Net Firm Transactions 7.1 7.1Total Potential Resources 53.2 28.0Adjusted Potential Resources 20.2 27.2Scenario Case(%)Due to the fact that ISO-NE uses a probabilistic methodology 46 to determine resource adequacyneeds, both the 2018 Summer Reserve Margin for the category Region/Sub-Region TargetCapacity and Reserve Margins are labeled “Not-Applicable (N/A)”, for both the Reference Caseand Scenario Cases. Within prior NERC Long-Term Reliability Assessment submittals, these twovalues have not applied, and unless ISO-NE changes its forward-going methodology todetermine New England’s annual resource adequacy requirements, they would not apply goingforward.The NERC 2018 Summer Reserve Margins for the category Existing Certain and Net FirmTransactions shows a 7.1 percent margin for both the Reference Case and the Scenario Case.This is because both the Reference and the Scenario Case have the same assumptions forExisting (Certain and Other) Capacity, Future (Planned and Other) Capacity and CapacityTransactions (Imports and Exports).The 2018 Summer Reserve Margins for the category Total Potential Resources shows a 53.2percent margin for the Reference Case and a 28.0 percent margin for the Scenario Case. Thisdifference is due to the fact that within both the Reference Case and the Scenario Case, 100percent of the identified Conceptual Capacity was added to the Total Potential Resourcesmargins. The Reference Case Conceptual Capacity (12,462 MW) is 7,808 MW greater than thatof the Scenario Case Conceptual Capacity (4,654 MW). The Reference Case Total PotentialResources margin (53.2 percent) is almost twice as much as that of the Scenario Case TotalPotential Resources margin (28 percent).The 2018 Summer Reserve Margins for the category, Adjusted Potential Resources, shows a20.2 percent margin for the Reference Case and a 27.2 percent margin for the Scenario Case.46 ISO-NE uses the Loss of Load Expectation (LOLE) method for determining New England’s annual resourceadequacy needs, which in short, accounts for the probabilistic variations in both load and resource availability.2009 Scenario Reliability Assessment Page 65