By Rich Heidorn Jr.

ISO-NE has identified a 160-MVAR reactor at National Grid’s Golden Hills 345-kV substation in Saugus, Mass., as a key part of its solution to Boston’s 2028 needs, the RTO’s Kaushal Kumar told the Planning Advisory Committee on Thursday. The reactor, at an estimated cost of $5.47 million, is intended to correct high-voltage violations found at minimum load levels.

Kumar, a senior transmission planning engineer, said the solution was chosen from four 115-kV and 345-kV alternatives in the RTO’s final review. All the finalists also require the installation of a 115-kV breaker in series with breaker 4 at Exelon’s Mystic generating plant to eliminate a breaker failure contingency, a project estimated at $3.25 million.

Together, the two solutions are estimated at $8.72 million (+50%/-25%).

Kumar said the cost estimate and expected in-service date were the most important factors in the RTO’s selection.

The winning project was the cheapest among the options that could be in service in 2021.

Because it is time-sensitive, it will be installed by National Grid. A need is considered time-sensitive — and excluded from competitive bidding — if the improvements are required within three years of a completed needs assessment.

Needs Update Reduces Thermal Violations

The RTO also briefed the PAC on its updated study of non-time-sensitive needs in the Boston study area, which will be the subject of a request for proposals in the fourth quarter. The update incorporates the Golden Hills reactor and system changes since the finalization of the Boston 2028 Needs Assessment in June.

The update made several changes to resource assumptions:

• The New England Clean Energy Connect (NECEC) and Revolution Wind offshore wind projects were added to the model after providing approved contracts to the RTO. NECEC, a transmission line that would deliver Canadian hydropower to New England, was modeled as a 1,090-MW injection at the Larrabee Road 345-kV substation in Maine. Revolution Wind was modeled as a 120-MW injection at the Davisville 115-kV line in Rhode Island. Both were modeled at 20% of their nameplate capacity.
• Resources that filed retirement and permanent delist bids for Forward Capacity Auction 14 were removed from dispatch assumptions.
• The model uses FCA 13 active demand capacity resources (ADCRs), updated from FCA 12.
• Resources outside Boston that filed retirement and permanent delist bids for FCA 13 have been removed from dispatch.
• An “asset condition” project to refurbish the 110-510/511 cables in downtown Boston was added.

The needs assessment posted on June 10 identified one N-1 and six N-1-1 thermal violations under peak loads, all considered non-time-sensitive needs. The updated analysis eliminated three N-1-1 thermal violations: on the Woburn-Wakefield Junction 345-kV and Stoughton-to-K Street 345-kV circuits 1 and 2.

Four other thermal violations identified in the June 2019 Needs Assessment remain:

• N-1 Thermal Overload: W. Amesbury–King St. 115-kV line;
• N-1-1 Thermal Overload: circuits 1 and 2 of the Woburn-North Cambridge 345-kV lines; and
• N-1-1 Thermal Overload: North Cambridge–Mystic 345-kV cable.

Mystic Reactor

ISO-NE’s Pradip Vijayan updated the PAC on revisions to the requirements for a 300-MVAR dynamic reactive device needed for system operations after the retirement of Mystic Units 8 and 9. Exelon announced last year that it would retire Mystic in 2022, but FERC approved a cost-of-service agreement between the company and ISO-NE to keep Units 8 and 9 operating through May 2024.

Since the Aug. 8 PAC meeting, RTO staff reduced the device’s requirement to provide full leading capability at 1.05 per unit voltage at the point of interconnection (POI), down from the original 1.1. The requirement to provide full lagging capability at 0.9 per unit voltage is unchanged.

Staff also amended some of the reactive power requirements for clarity, saying the device must provide continuous voltage control at the POI and must not stay in standby mode (providing no reactive power) under normal operating conditions.

The reactor is considered non-time-sensitive.

The RTO plans to finalize the Boston 2028 Solutions Study next month. Stakeholder feedback on the selection and the study report, which was posted Sept. 24, are due on Oct. 9. Comments should be sent to pacmatters@iso-ne.com.

“You can look for an RFP [on the non-time-sensitive needs] in December,” said the RTO’s Eva Mailhot. “That’s our Christmas present to you guys,” she joked.

Eastern Connecticut 2029 Needs Assessment

ISO-NE’s Jon Breard provided an update on the Eastern Connecticut (ECT) 2029 Needs Assessment, which was suspended in February because changes in the 2019 draft capacity, energy, loads and transmission (CELT) forecast indicated the net load figures in the ECT 2027 assessment were too high. The 2019 CELT shows changes in load, energy efficiency and solar PV from the 2017 CELT.

The revised ECT needs assessment considers future load forecasts, resource changes based on FCA 13 results, coordination with proposed Southeastern Massachusetts and Rhode Island (SEMA/RI) projects, and NERC, ISO-NE and Northeast Power Coordinating Council (NPCC) reliability standards.

Also included were NECEC and the Vineyard Wind and Revolution offshore wind farms.

The CELT 2029 90/10 summer peak load forecast is 32,468 MW, an increase of 1,663 MW over the 2022 forecast. However, net load excluding station service decreased by 100 MW because of increased forecasts for energy efficiency and PV production.

The report concludes that non-transmission options were not able to correct the reliability violations in ECT.

All needs are time sensitive and located on the systems of Eversource Energy, National Grid and Connecticut Municipal Electric Energy Cooperative, the RTO said.

The RTO plans to post the draft ECT needs assessment next month, with the final report expected to be posted in the fourth quarter.

The study found no N-0 violations in ECT or neighboring areas and one N-1 low-voltage violation and no N-1 thermal violations in the ECT area. Steady-state peak load results identified seven N-1-1 violations.

The RTO plans to post the final needs assessment report in the fourth quarter.

Transmission Planning Technical Guide Short-circuit Requirements

The RTO’s Faheem Ibrahim briefed the committee on proposed assumptions for conducting short-circuit analyses using an ASPEN OneLiner.

Such analyses are used in generator interconnection studies, system impact studies, needs assessments, solution studies, and NERC and NPCC compliance studies.

Ibrahim said having a single set of study conditions and solution parameters in the Transmission Planning Technical Guide will ensure consistency across the different studies.

Comments on the revised guide are due to pacmatters@iso-ne.com by Tuesday.