ISO-NE’s Regional Energy Shortfall Threshold (REST) will rely on a pair of metrics intended to capture the intensity and duration of energy shortfall risks in extreme weather scenarios, the RTO told the NEPOOL Reliability Committee on Nov. 19. 

The REST project is an effort to define an acceptable threshold for ISO-NE’s seasonal risk modeling, which will use the RTO’s newly developed probabilistic energy adequacy tool (PEAT). ISO-NE plans to use the REST to evaluate whether additional actions will be needed to support system reliability ahead of winter and summer seasons. 

The modeling features a “multiday rolling-horizon economic dispatch,” which includes both preventive and corrective measures from the RTO and incorporates generator opportunity costs. (See ISO-NE Boosts Energy Adequacy Modeling Capabilities.) 

In the seasonal outlook for the upcoming winter — which marks ISO-NE’s first time using the PEAT in a seasonal analysis — the RTO’s modeling found manageable shortfall risks. (See ISO-NE Sees Manageable Shortfall Risk for Upcoming Winter.) In the future, the REST and its associated metrics are intended to help standardize this evaluation. 

To assess the magnitude of shortfall risks, ISO-NE plans to calculate the normalized unserved energy (NUE), defined as total shortfall relative to demand, over the most extreme 72-hour cases identified by the model. This will indicate what percentage of load would experience shortfall in the low-probability events identified. 

To evaluate shortfall duration, the RTO will calculate the length of the most extreme scenarios, looking beyond the 72-hour window used to calculate intensity. 

Mike Knowland, manager of operations forecast and scheduling for ISO-NE, said the duration and magnitude metrics will complement each other and are both “critical metrics for assessing energy adequacy risk under extreme conditions.” He added that ISO-NE “is still evaluating how best to incorporate these two metrics into its REST proposal.” 

ISO-NE still is taking feedback on the proposed metrics, and it plans to continue stakeholder discussions on the proposal through January or February of 2025. Once the metrics are established, the RTO plans to present an initial proposal on risk thresholds in March or April. 

The establishment of the REST directly relates to how much the region is willing to spend to limit the potential reliability effects of low-probability weather events, and it could raise tough questions about the tradeoffs between reliability, affordability and decarbonization. ISO-NE has indicated it expects the states to play a major role in establishing this threshold. 

NECEC Agreements

Also at the RC, ISO-NE reviewed the Transmission Operating Agreement and Interconnection Operators Agreement for the New England Clean Energy Connect (NECEC) transmission line.  

The 1,200-MW line was solicited by Massachusetts and would facilitate additional imports from Hydro-Québec. Avangrid, the project developer, recently indicated the line has a best-case in-service date of January 2026. (See Avangrid Sues NextEra over ‘Scorched-earth Scheme’ to Stop NECEC.) 

ISO-NE plans to file the agreements with FERC in the first half of 2025 and seeks an advisory vote from the RC on the interconnection agreement, as well as a vote from the NEPOOL Transmission Committee on the transmission agreement.  

The TOA between ISO-NE and NECEC would give the RTO operating authority over the line, which includes responsibility for generation dispatch, real-time balancing, establishing operating limits and exchanging transmission security information to the relevant parties. 

The agreement also includes “a standard ‘grandfathered agreements’ provision,” which includes rights of Massachusetts’ electric distribution companies to receive power from the line, ISO-NE said. These rights can be overridden by “short-term reliability actions.” 

The interconnection agreement between Hydro-Québec and ISO-NE governs the “coordinated operation and scheduling of energy and ancillary services,” emergency energy exchanges, outage scheduling and the “treatment of inadvertent interchange.” 

While the NECEC contracts between Massachusetts’ EDCs and Hydro-Québec are intended to facilitate the one-way flow of power from Canada to the U.S., the line will be capable of sending power in both directions, ISO-NE said. This will allow for emergency south-to-north transmission, although the system impact of these flows still needs to be studied, the RTO added. 

The RC is scheduled to vote on the interconnection agreement in January 2025. 

Planning Procedure for Data Collection

Steven Judd, ISO-NE manager of resource adequacy and accreditation, outlined the RTO’s proposal for a new planning procedure (PP-14) focused on generator data reporting requirements, which is intended “to provide structure and guidance for lead market participants responsible for reporting monthly data.” 

“This procedure will describe the data submission timelines, reporting requirements and validation processes for the required data,” Judd said. He added that standardizing the reporting requirements and guidelines will help ensure system reliability. 

The RC will vote on the proposal in January 2025.