ISO-NE’s draft 10-year Capacity, Energy, Loads and Transmission (CELT) forecast is reducing projected summer loads in 2026 by nearly 6% in part because of a sharp increase in projected energy efficiency, RTO officials told the Planning Advisory Committee on Thursday.

The draft 2018 CELT reduces the net annual energy forecast by 4.5% lower in 2025 with the net summer 2026 50/50 forecast reduced by 6.0% and the summer 90/10 forecast cut by 5.8%.

The behind-the-meter solar photovoltaic forecast for 2026 is about 0.6% higher, with energy efficiency boosted by 16.2%. The new report foresees about the same regional economic growth through 2026 as last year’s forecast.

The gross 50/50 load forecast — calculated before reductions from passive demand resources (PDR) and behind-the-meter PV — was cut by 2.7%, and the gross 90/10 forecast was 2.8% lower. The gross annual energy consumption forecast increased by 0.3%.

The solar PV forecast included the expected impact of the tariffs imposed on solar panels by the Trump administration. It also includes a 0.5%/year PV degradation rate to account for solar panels’ declining conversion efficiency over time, based on research by the National Renewable Energy Laboratory.

The RTO develops the CELT 10-year forecast as part of its annual forecast process.

The finalized forecasts will be shared at the April 26 PAC and published by May 1.

Update on Transmission Projects

ISO-NE has put 22 upgrades in service since October, the RTO said in its transmission projects and asset condition update, including the new Scobie–Tewksbury 345-kV line and five other projects in the Boston area.

The RTO reported an $11.9 million increase in the estimate cost for Project 945–Adams in Central Western Massachusetts (installing two new 115-kV breakers and replace two existing 115-kV breakers and associated line relocations). The cost increased because of “an enhanced understanding of the multiple site condition impacts on the construction plan,” the RTO said.

That increase was more than offset by a $12.3 million reduction in the estimated cost of Pittsfield/Greenfield Projects 1662, 1664, 1665 and 1663 because of “project cost alignments.”

No new reliability or market efficiency-based transmission system upgrades have been added to the Regional System Plan project list since October. However, 36 new projects totaling $549.5 million have been added to the Asset Condition list, largely for the replacement of aging infrastructure.

Eastern Connecticut 2027 Needs Assessment

The PAC heard an update on the 2027 Eastern Connecticut (ECT) Needs Assessment, which is evaluating reliability needs for the 10-year period extending until 2027.

The draft needs analysis found violations of low-voltage and high-voltage reliability criteria for first and second contingencies as well as some severe thermal violations in some areas following second contingencies. All the violations were also found to be present in 2020.

ISO-NE announced the needs analysis last June. The previous ECT 2022 Needs Assessment report was finalized in June 2015 but work on solutions to address the region’s time-sensitive needs were suspended in February 2017 pending a review of RTO criteria, assumptions and methodologies impacting needs assessments and solutions studies.

The RTO said the review had “sufficiently progressed” to allow initiation of the new study.

The final scope of work was posted earlier this month, along with responses to stakeholder comments.

The study area is a rectangle bounded by the Long Island Sound on the south and the Massachusetts border on the north, with the eastern boundary the Rhode Island border and the western boundary just west of New London.

“This area hasn’t been studied in a long, long time,” said Brian Forshaw, a consultant for Connecticut Municipal Electric Energy Cooperative (CMEEC). “So, we’re glad to see things are progressing from a needs assessment to solutions studies.”

He said, however, that the needs assessment was “more limited than it should have been” and criticized the “top-down” load forecast.

The finalized needs assessment will be posted by May 31. The RTO will work with Eversource Energy and CMEEC to address the needs on their transmission systems.

Eversource Equipment Replacements

Eversource made a presentation on the replacement of its Montville 16X 115/69-kV transformer, which is at its end of life after 67 years. Total project cost is estimated at $6.3 million (-25%/+50%).

The company also provided an update on replacement of the Card Street 11F-5X autotransformer, which was originally presented in September.

The September PAC presentation recommended its replacement with a three-phase spare unit located at the Montville 4J Substation. Eversource said it conducted a re-evaluation that determined the summer long-term emergency rating of the replacement could be increased from 458 MVA to 512 MVA. The existing autotransformer is rated at 491 MVA. The estimated cost remains $8.6 million (+50%/-25%).

Transmission Planning Technical Guide

ISO-NE is continuing its revisions to the Transmission Planning Technical Guide, which was reorganized last year to a new format with four main sections: Introduction, Modeling Assumptions, Reliability Criteria and Guidelines, and Analysis Methodology.

Revision 2 was posted on the ISO website on Nov. 14, 2017.

Staff is now updating the appendices for consistency with the RTO’s style guide and publication template:

• App. A – Terms and Definitions (Expected Q2 2018): Adding/removing terms and definitions; adding references to NERC and Northeast Power Coordinating Council glossary of terms.
• App. B – Fast Start Generation List: Retired after change to probabilistic methods for base case dispatches of transmission needs assessments and solution studies.
• App. C – DR Modeling Guide (Expected Q2 2018): New terminology associated with price responsive demand (PRD).
• App. D – Damping Criteria: Retired after criteria moved to Section 3.3.3 of Technical Guide.
• App. E – Voltage Sag Guideline (Expected Q2 2018): Update to clarify methodology.
• App. F – 2000 STF Memo (Draft Posted March 2018): Updated diagrams for clarity.
• App. G – Phase Shifter Guide (Draft Posted March 2018): Changed name from Modeling Guide to Phase Shifter Guide to focus on content of appendix; remove Sackett Phase Shifter and 3rd Waltham Phase Shifter; update all descriptions to match current operating practices.
• App. H – No-Fault Contingencies (Draft Posted March 2018): Updated to current version of Planning Procedure No. 3.
• App. I – Transfer Methodology (Draft Posted March 2018): Reorganized structure to align with Technical Guide format; new terminology associated with PRD.
• App. J – Load Modeling Guide (Draft Posted March 2018): Added descriptions for solar PV modeling; added equations to explain methodologies; new terminology associated with PRD; adding Area-Owner-Zone-Bus assignments.

Stakeholders can provide comments for 15 days after the posting of each document on the PAC website to PACMatters@iso-ne.com. Comments on Appendices F, G and H are due April 3.

The PAC’s next meeting is April 26 at the Doubletree Hotel in Milford, Mass.

— Rich Heidorn Jr.