NYSEG Fraser Substation Upgrade: 345 kV to 115 kV Logic
Project Context: NYSEG Launches Oneonta South Area Grid Upgrade
On 10 September 2026, Transformer Magazine reported that New York State Electric & Gas (NYSEG) has completed the upgrade of the Fraser substation in Oneonta, New York, marking a key substation upgrade milestone as the first phase of its Oneonta South Area Improvements Project. The core work adds a new 115 kV substation yard to a site that previously carried only 345 kV switchgear, and installs a new power transformer in the existing 345 kV yard to support growing demand in the Fraser and Delhi areas.
The equipment scope is modest, one 115 kV yard and one transformer, but the project illustrates how US northeastern utilities are responding to the dual pressure of ageing 1960s–1970s infrastructure and 2-3 year domestic transformer lead times, by staging capital projects into reviewable, regulator-friendly phases.
For context on how another transmission utility is approaching a brownfield substation upgrade of similar scope, see our recent analysis of the Dublin 220 kV Poolbeg substation upgrade engineering logic.
1.1 NYSEG and the Avangrid / Iberdrola Framework
NYSEG, together with Rochester Gas and Electric (RG&E), sits within the Avangrid network of US utilities. Iberdrola completed the acquisition of the remaining Avangrid shares in 2025, making Avangrid a wholly-owned US subsidiary of the Spanish parent.
This structure directly shapes NYSEG’s capex cadence. Iberdrola-style T&D investments follow a five-year rolling plan with annual adjustments, each cycle requiring approval from the New York State Public Service Commission (NYPSC). Within the 2024-2028 cycle, Avangrid’s total New York State T&D capex is in the order of USD 4.7 billion, with NYSEG and RG&E each among the top five IOUs in the state by approved spend.
The Fraser substation upgrade is one of the more visible discrete projects inside that envelope.
For broader coverage of substation engineering, supply chain dynamics and grid investment patterns, browse our substation engineering archive.
1.2 The Original Role of Fraser Substation
The Fraser substation sits on Hamden Hill Road in Oneonta, Otsego County, New York, roughly 100 km southwest of Albany, home to about 13,000 residents. The site was originally commissioned in 1969 and is therefore 57 years old at the time of the upgrade.
Historically, Fraser functioned as a 345 kV through-substation along a state-level transmission corridor, carrying bulk transit power rather than serving significant local load. That “transit” role is why the original layout carried minimal transformation capacity and limited sub-transmission build-out.
Three structural shifts in the region since the mid-2010s have changed that calculus: distributed generation interconnection requests, modest data centre load growth in upstate New York, and capacity bottlenecks on the existing 46 kV sub-transmission network connecting Oneonta and Delhi. Together they drove NYSEG to overlay a 115 kV yard on a 345 kV site, converting a single-voltage transit node into a two-voltage hybrid station.
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1.3 The Wider Oneonta South Area Improvements Project
The Fraser upgrade is the first phase of the Oneonta South Area Improvements Project. The wider programme has three components:
| Phase | Scope | Status |
|---|---|---|
| Phase 1 (now complete) | Fraser 115 kV yard + new 345/115 kV transformer | Completed Sept 2026 |
| Phase 2 | Delhi substation (Sherwood Road) upgrade | Expected to start later 2026 |
| Phase 3 | 46 kV / 115 kV line rerouting and new build between Fraser, Delhi and Oneonta | 2026 H2 to 2027 |
The phasing is deliberate. Phase 1 delivers new distribution-side capacity first, Phase 2 reinforces the upstream source substation, and Phase 3 ties the three sites together with new sub-transmission lines. The advantage of this staging is that each phase produces usable transmission capacity on its own, insulating the overall programme from any single-phase schedule risk.
The Significance of Adding a 115 kV Yard and a New Transformer
2.1 What the New 115 kV Yard Adds Functionally
The original Fraser site had no intermediate voltage stage between 345 kV and the local 46 kV sub-transmission network. In North American practice, 46 kV is firmly sub-transmission, with predominantly wood-pole lines and limited thermal and reliability headroom.
The new 115 kV yard changes that. Once energised, Fraser can: accept 115 kV line connections directly, bypassing the existing 46 kV backbone; perform the 345 kV to 115 kV transformation on site to feed Oneonta, Delhi and downstream substations; and reserve 115 kV feeder positions for future distributed energy resource interconnections.
The functional change is significant. Fraser shifts from a pure transit node to a hybrid transit-plus-local-supply node, with implications for both reliability metrics and operational flexibility.
2.2 Why a New 345 kV Side Transformer Is Required
Adding a 115 kV yard without a 345/115 kV transformer would amount to a stranded asset. The new transformer is therefore the lynchpin of the project.
Avangrid’s standard 345/115 kV transformer ratings on similar projects sit between 250 MVA and 450 MVA. The NYSEG release does not disclose the rating; only the fact that a new transformer has been added to the existing 345 kV yard. Industry typical values in this configuration would be 300 MVA or 350 MVA, with approximately 8-10% impedance and on-load tap-changer capability.
Three engineering functions are served: providing the 345/115 kV step-down path that the new yard depends on; forming an N-1 redundancy with any pre-existing 345/115 kV units; and reserving transmission capacity toward Delhi for future load growth.
2.3 Coexistence with 1969-Vintage Primary Equipment
Much of the original 345 kV bus, breakers and disconnectors at Fraser date to 1969 and are at or beyond typical 40-50 year design life. The new 115 kV yard and the new transformer, by contrast, are 2020s-vintage equipment with digital protection, SF6 or SF6-free GIS bays, and modern SCADA integration.
This “old site, new equipment” pattern is common across the US Northeast. A useful comparison is BC Hydro’s recently announced CAD 200 million Burnaby 60 kV substation modernisation, which retains the original 230 kV switchyard while comprehensively replacing the medium-voltage and protection system. The key difference is that Burnaby already had a 230/60 kV two-stage configuration, so the work there is a medium-voltage replacement; Fraser had only a single 345 kV stage, so the work here is the addition of an entirely new voltage tier.
Phase 1 Substation Upgrade Scope and Equipment Parameters
3.1 Scope of the Completed Phase 1 Works
Based on the NYSEG disclosure and Transformer Magazine coverage, Phase 1 consists of four work packages:
| # | Work Package | Voltage | Notes |
|---|---|---|---|
| 1 | New 115 kV substation yard | 115 kV | Bus, breakers, disconnectors, instrument transformers |
| 2 | New power transformer | 345/115 kV | Installed in the existing 345 kV yard |
| 3 | 115 kV transmission line interfaces | 115 kV | Positions reserved for multiple outgoing feeders |
| 4 | Protection, control and SCADA upgrade | Station-wide | Includes digital protection relays |
Combined, these packages convert Fraser from a single-voltage 345 kV station into a dual-voltage 345/115 kV station with multi-feeder 115 kV capability.
3.2 Topology and Voltage Tier Changes
The topology change is best understood as single-tier 345 kV becoming dual-tier 345/115 kV. Typical single-line implications: the 345 kV side retains its existing single-bus-with-bypass or breaker-and-a-half arrangement; the new 115 kV side adopts a single-bus sectionalised configuration with 4-6 feeder positions reserved; the transformer bay is terminated via SF6 breakers on both sides.
The choice of “high side untouched, low side built new” is common in US brownfield substation work because it minimises impact on the in-service 345 kV transmission corridor.
3.3 Service Area and Reliability Headroom
NYSEG’s public statement sets the project objective as “increasing transmission capacity and improving reliability for tens of thousands of customers in the region”. The expected reliability benefits fall into three categories: reduced loading on the Oneonta south and Delhi 46 kV sub-transmission feeders; reduced exposure to long 46 kV wood-pole line outages via direct 115 kV supply; and the availability of redundant supply paths under N-1 contingencies.
Quantitative SAIDI and SAIFI deltas will only become visible after NYSEG files its next rate-case performance report, but the structural reliability improvement is consistent with the equipment choices described above.
Phase 2 Delhi Upgrade and Phase 3 Line Reroute Outlook
4.1 Delhi Substation Upgrade Content
Delhi substation sits on Sherwood Road, roughly 25 km from Fraser, and is the other key node in the Oneonta south system. Phase 2 is expected to include transformer capacity addition or replacement, upgrade or new build of 115 kV switchgear, comprehensive protection and control system replacement, and associated transmission line interface modifications.
The existing Delhi voltage configuration is 46 kV. Once Phase 2 lands, Delhi will receive 115 kV supply from Fraser and step down to 46 kV locally, mirroring the 115/46 kV two-tier architecture that Phase 1 establishes at Fraser.
4.2 Transmission Line Rerouting and New Build
Phase 3 covers the rerouting and new build of 46 kV and 115 kV lines connecting Fraser, Delhi and Oneonta. Anticipated work includes retirement of selected 46 kV wood-pole lines, new 115 kV steel-pole or tubular-steel construction, and partial route realignment to avoid ecological and built-up constraints.
This “build new before decommission old” sequencing is standard practice in regions where the existing sub-transmission grid is more than half a century old.
4.3 Overall Project Milestones (H2 2026 to 2027)
| Stage | Timing | Key Milestone |
|---|---|---|
| Phase 1 (Fraser upgrade) | Completed September 2026 | Reported in this article |
| Phase 2 (Delhi upgrade) | Construction start later in 2026 | NYSEG-stated target |
| Phase 3 (Line reroute / new build) | H2 2026 to 2027 | Coordinated with Phase 2 |
| Overall project completion | 2027 | Programme-level target |
The defining feature is the overlap between Phases 1 and 2, with Phase 3 deliberately sequenced after Phase 2 because new line interfaces depend on the upgraded substation bays being available.
Supply Chain and Construction Logic in the US Northeast Upgrade Wave
5.1 NYSEG Capex and Regulatory Mechanics
As an investor-owned utility, NYSEG’s capex is regulated by the New York State Public Service Commission under a rate-case mechanism with typical review cycles of 10 to 14 months. The current cycle covers 2024 to 2028 with NYSEG company-wide capex of approximately USD 1.9 billion.
The regulatory mechanics influence project pacing in three ways: major capex requires NYPSC pre-approval; project execution must follow the approved budget and schedule, with material variances requiring regulatory explanation; and post-completion, investments undergo “Used and Useful” review. This combination pushes NYSEG toward staged filing, staged approval and staged construction, exactly the Oneonta South pattern.
5.2 Construction Pacing under 2-3 Year Transformer Lead Times
US domestic large power transformer lead times have remained at 2-3 years, and that supply tension directly affects procurement strategy for the new Fraser unit. Typical NYSEG responses include: placing the transformer order 18-24 months ahead of the energisation target; selecting a standardised MVA rating (300 or 350 MVA) to maximise the pool of qualified domestic manufacturers; and completing civil works and the 115 kV yard before the transformer arrives, so the unit can be installed and commissioned within weeks of delivery.
This “civil first, electrical later” sequencing is increasingly common across US IOUs.
5.3 Cross-Project Comparison with BC Hydro, TenneT and Elia
| Project | Owner | Investment | Voltage | Work Type |
|---|---|---|---|---|
| Fraser upgrade (this article) | NYSEG (US) | Estimated USD 100-200 million | 345/115 kV | New voltage tier on aged site |
| BC Hydro Burnaby upgrade | BC Hydro (Canada) | CAD 200 million | 230/60 kV | MV-side replacement on aged site |
| TenneT USD 3 B green bond | TenneT (Germany) | USD 3 billion | 380 kV HVDC | New offshore wind connection |
| EIB-financed Princess Elisabeth Island | Elia (Belgium) | EUR 1.2 billion | 380 kV AC + 220 kV DC | Artificial energy island grid link |
The common driver across these projects is the combination of ageing infrastructure and new demand, but the engineering strategies diverge. Fraser adds a voltage tier, BC Hydro replaces a voltage tier, TenneT builds a brand-new HVDC overlay, and Elia builds a special-purpose offshore grid link. The pattern suggests that US northeastern IOUs prioritise life extension and capacity addition, while European TSOs focus on new-build and renewable integration.
Conclusion: The Life-Extension Path for a 57-Year-Old Site
Beyond the mechanics of this particular substation upgrade, the Fraser project is mechanically simple, a new 115 kV yard plus a new 345/115 kV transformer, but its engineering significance extends well beyond the equipment count. It illustrates how utilities can add a voltage tier on a 1960s-vintage site to extend useful life and add capacity without rebuilding from greenfield.
The wider programme is scheduled for completion in 2027, at which point Fraser will have transitioned from a 57-year-old single-voltage transit station into a dual-voltage hybrid station capable of serving Oneonta south for the next 10-20 years. Read together with the BC Hydro Burnaby project, the TenneT offshore wind programme and the Elia Princess Elisabeth Island link, the Fraser upgrade is one more data point in the 2020s grid investment cycle across North America and Europe, with each utility applying a different engineering strategy to the same underlying “old assets, new demand” substation upgrade challenge.