Binding Transmission Constraints — CY23 Study Results
| Interface | Zone | Constrained Element | Voltage | SDU / SUF Cost | Study Finding |
|---|
| LI Byway | K | Pilgrim-West Bus 138kV PAR + 2 UG cable circuits | 138kV | $295–334M SDU | Binding — All LI storage |
| Dunwoodie South | J | Mott Haven-Rainey East/West 345kV reconductoring | 345kV | $220M SUF | SUF Required |
| Dunwoodie South | J | Mott Haven 345kV — 2x20 MVAr shunt reactors | 345kV | $159M SUF | SUF Required |
| Dysinger East | A | Hillside 230kV PAR — headroom reuse | 230kV | $14.3M headroom | Headroom Payment |
| NY-PJM | C/A | Hillside-East Towanda 230kV PAR | 230kV | $14.3M headroom to Q596 | Headroom Payment |
| LIPA Import | K | Dunwoodie-Shore Road 345kV | 345kV | 1,621 MW normal limit | At Limit |
| Total East | E/F | Marcy-Coopers Corners 345kV | 345kV | No SUF triggered | Clear — CY23 |
| Moses South | D | Willis-Haverstock 345kV (Q1125) | 345kV | No SUF triggered | Clear — CY23 |
| Volney East | C | Edic-Princetown 345kV | 345kV | No SUF triggered | Clear — CY23 |
Fault Current Issues — Overdutied Breakers & Mitigations
Zone J — ConEd 345kV
Farragut, BCEH, Gowanus, East 13th St — Overdutied
Fault current exceeds lowest FID rating in ATRA case. Triggered by Q1016 EI Steinway 1, Q1017 EI Steinway 2, Q1199 El Steinway 1.1 at Mott Haven 345kV. Mitigation: switching on series reactors SR41 + SR42 at Gowanus 345kV substation. No separate SUF — operational measure.
CY23 Facilities Study Section 7.2, Table 23-24
Zone C/B — NYSEG 115kV
Hillside + New Gardenville — Overdutied Breakers
Not flagged in preliminary bus fault screening — identified only during individual breaker analysis (IBA). Hillside 115kV breaker 96212: $703K SUF (Q1036 Mainesburg ESS). New Gardenville 115kV breaker T10-12: $630K SUF (Q785 58% + Q852 42%).
CY23 Facilities Study Section 7.2, Table 22
Zone A/D — NGrid + NYPA
Edic 345kV, New Scotland 345kV, St Lawrence 230kV
Fault current exceeded lowest FID but upon review breakers were already scheduled for replacement by the TO. No additional SUF allocated to CY23 projects. No cost impact.
CY23 Facilities Study Section 7.2
Zone J/K — BPS Classification
7 New Buses Classified as Bulk Power System
NEW_AST_EST1 + EST2 345kV (Q1016/Q1017/Q1199 POIs), Ruland Road 345kV (Q680 POI), Q866 POI 345kV, Q1089/Q1115 POI 345kV, Q1183 POI 345kV, Q1184 POI 345kV. All designed to meet NPCC Directory 4/8/11 standards — no additional SUF required for BPS classification itself. Ruland Road 345kV BPS upgrade: $5.9M SUF to Q680 Juno Power Express.
CY23 Facilities Study Section 5.3, Table 20
SSTI Screening — Subsynchronous Torsional Interaction Risks
Q1016 / Q1017 / Q1199 — EI Steinway
Potential Interaction with Rainey GT10 + Ravenswood 3
UIF exceeds 0.10 threshold at N-4 to N-7 conditions. Developer must perform time-domain PSCAD simulations with multi-mass models. If damping unsatisfactory, HVDC/inverter control dynamics must be adjusted. Results to be provided to NYISO during detailed design phase.
CY23 Facilities Study Section 6.1, Table 21
Q1288 — CPNY-X
Potential Interaction with Rainey GT10 + Ravenswood 3
UIF 0.315 with Rainey GT10 at N-4 (highest of any CY23 project). Also 0.252-0.278 with Ravenswood 3-1/3-2. Same PSCAD simulation requirement as EI Steinway. Interaction is internal to NYSTS in most scenarios.
CY23 Facilities Study Section 6.1, Table 21
Q822 — Whale Square Energy Storage
Potential Interaction with Kent Ave (UIF 0.595)
Highest UIF among storage projects at N-6. Kent Ave UIF 0.595. Also Narrows GT1/GT2 and Gowanus units at various N-conditions. N-1 interaction with Narrows GT2 is internal to the generating facility — not a NYSTS concern.
CY23 Facilities Study Section 6.1, Table 21
Capacity Retirements Modeled in CY23 ATBA System
| Unit | Owner | Zone | CRIS MW (Summer) | Status | Reason |
|---|
| Indian Point 2 | Entergy | H | 1,026.5 | Retired | Nuclear retirement |
| Indian Point 3 | Entergy | H | 1,040.4 | Retired | Nuclear retirement |
| Somerset | Somerset Operating Co. | A | 686.5 | Retired | Coal retirement |
| Nassau Energy | ENGIE | K | 51.6 | Retired | Age/economics |
| Gowanus 1-1 through 1-8 | Astoria Generating | J | ~137 | Retired | DEC Peaker Rule |
| Gowanus 4-1 through 4-8 | Astoria Generating | J | ~138 | Retired | DEC Peaker Rule |
| Hudson Ave 3 + 5 | Con Edison | J | 31.1 | Retired | DEC Peaker Rule |
| Shoreham 1 + 2 | National Grid | K | 67.4 | Deactivated | DEC Peaker Rule (LIPA reliability waiver until May 2025) |
| Glenwood GT 03 | National Grid | K | 54.7 | Deactivated | DEC Peaker Rule (LIPA reliability waiver until May 2025) |
| Northport GT | National Grid | K | 13.8 | Deactivated | DEC Peaker Rule (LIPA reliability waiver until May 2025) |
| Gowanus 2-1 through 2-8 | Astoria Generating | J | 152.8 | Seasonal | DEC Peaker Rule — out May-Sep ozone season |
| Gowanus 3-1 through 3-8 | Astoria Generating | J | 146.8 | Seasonal | DEC Peaker Rule — out May-Sep ozone season |
| Narrows 1-1 through 2-8 | Astoria Generating | J | 309.1 | Seasonal | DEC Peaker Rule — out May-Sep ozone season |
| Arthur Kill GT 1 | NRG Power Marketing | J | 16.5 | Deactivated | DEC Peaker Rule compliance plan |
Key Transmission Additions — CY23 ATBA 5-Year Plans
Zone A/B — Q580
STAMP Substation + Dysinger 345kV PAR
NextEra Q545A Dysinger New Station + East Stolle New Station 345kV, 1,356 MVA summer rating, in service 2022. STAMP substation (Q580 NYPA/NGrid) 345/115kV 300 MVA in service 2024. Significantly improves Dysinger East transfer capability — West Central transfer increased 588 MW in CY23 ATRA.
CY23 Facilities Study Table 7
Zone F/G — Q543/Q556
New York Transco Knickerbocker + Van Wagner 345kV
Knickerbocker New Station to Pleasant Valley 345kV 54.5 miles, 3,844 MVA. Van Wagner New Station to Pleasant Valley 345kV. Dover Phase Shifter 345kV. Series capacitor at Knickerbocker. Total East and UPNY-SENY transfer capability significantly improved.
CY23 Facilities Study Table 7
Zone K — CY21 SDUs
Holbrook 138kV + New Bridge 138kV BPS Upgrades
CY21 Sunrise Wind funded Holbrook 138kV BPS upgrade $15.6M. CY21 EI Oceanside 2 funded New Bridge 138kV BPS upgrade $13.9M. Both are Contingent Facilities for CY23 — if delayed, impacts CY23 cost allocations. CY23 projects owe functional headroom to both.
CY23 Facilities Study Section 1.5
Zone A — Q1125 Moses-Adirondack
NYPA Moses-Adirondack 345kV Uprate — 2,177 MVA
Major upstate transmission expansion. Moses to Haverstock, Haverstock to Adirondack, Adirondack to Austin Road, Austin Road to Edic — all 345kV. In service 2025. Moses South transfer increased 331 MW in CY23 ATRA. Enables large upstate wind + solar interconnection.
CY23 Facilities Study Table 7, Q1125