2000 kW Long-Duration Storage Substation: N+1 Main Transformer + 8 h/16 MWh, Grid-Code & Capacity Deep-Read
2000 kW PCS · 8 h/16 MWh LDES · 2×S13-M-2000/35 main transformer (N+1) · 35 kV feed · 83 clusters
1 · TL;DR Conclusion
Conclusion: this 2000 kW long-duration storage substation uses a 2000 kW PCS + 16063 kWh/8 h battery (83 clusters · 768 V DC) + 2×S13-M-2000/35 large main transformers (N+1) on a 35 kV grid. nMinus1 passes (84% loading after one transformer out); peak shaving ($0.13/kWh spread) saves ≈$379,600/yr; equipment ≈ $2,314,905, EPC ≈ $2,900,000 (feasibility-level).
- •LDES 2000 kW / 16063 kWh = 8 h, DOD 0.9 (17848 kWh rated), 83 clusters × 215 kWh, 768 V DC
- •Large main transformer 2×S13-M-2000/35 (N+1); nMinus1 passes — 84% loading after one unit out
- •Shaving: 2000 kW × 4 h × $0.13/kWh = ≈$379,600/yr (V24 basis)
- •35 kV feed; short-circuit LV 36.54 kA, breaking 50 kA (1.4×) · HV 25 kA (3×)
- •Losses 4,510,068 kWh/yr ($541,208/yr); SH15 amorphous upgrade pays back in just 2.4 yr
2 · Solution Overview
Long-duration energy storage (LDES) delivers 4+ hour — even multi-day — charge/discharge for multi-day peaking, frequency regulation and reserve, typically via flow batteries, pumped hydro or compressed air. This is a 2000 kW station with 8 h/16 MWh duration, on a 35 kV grid, with 2×2000 kVA main transformers (N+1).
| Source | Role | Share kW | Share |
|---|---|---|---|
| Grid 35 kV | base | 0 kW | 0% |
| BESS 2000 kW / 16000 kWh | variable | 1600 kW | 100% |
3 · Design Process & Rationale
1. Requirement identification
A long-duration station centers on duration and capacity (2000 kW · 8 h); the deciding points are the large main transformer and the grid-code basis — targeting multi-day peaking, frequency regulation and reserve.
2. Duration sizing
2000 kW PCS × 8 h = 16063 kWh usable (DOD 0.9 → 17848 kWh rated), 83 clusters × 215 kWh at 768 V DC; 8 h is a typical long-duration tier (pumped / compressed-air / flow).
3. Large main transformer
2000 kW / 0.95 ≈ 2105 kVA → 2×2000 kVA (N+1, one unit carries 84%), S13-M-2000/35 — meeting large-capacity connection and reliability.
4. Redundancy design
N+1 makes nMinus1 pass: after one transformer out, the remaining 2000 kVA covers 84% of load (sdKva 1684), ensuring continuous supply.
5. Protection & coordination
50/51 overcurrent grading; IEC 60909 short-circuit LV 36.54 kA, LV breaking 50 kA (1.4× margin) and HV 25 kA (3×), V19 passes.
6. Power quality
High-power PCS rectifier harmonics THDi 20% → detuned reactor + APF/SVG; reactive compensation holds PF ≥ 0.95.
7. Losses & economics
The large transformer loses 4,510,068 kWh/yr ($541,208/yr), a meaningful share; SH15 amorphous upgrade saves 6,920 kWh/yr and pays back in just 2.4 yr.
8. Grid code
35 kV high-side metering needs CT 0.2S / PT 0.2 (V12); LDES connection must be confirmed against the local grid code (ramp / primary frequency / LVRT).
Pain Points → Solution → Evidence
Large-capacity connection demands high transformer reliability/redundancy
2×2000 kVA main transformers in N+1, nMinus1 passes
nMinus1 verdict=pass · sdKva 1684 · 84% loading after one out
8 h long-duration battery is huge and capital-heavy
2000 kW × 8 h = 16 MWh (83 clusters · 768 V DC)
capacitySummary storageHours=8; storageBattery 83 clusters
Large-transformer losses drive up long-run bills
SH15 amorphous main transformer saves 6,920 kWh/yr
transformerTco.upgrade: 2.4 yr payback · $830/yr
Grid-code requirements (ramp / frequency / LVRT) unclear
35 kV high-side metering + IEC compliance + grid-code confirmation
V12 metering requirement; toConfirm gridCodeNote pending
4 · Key Parameter Deep-Read
| Parameter | Value | Basis | Impact & Boundary |
|---|---|---|---|
| Main transformer | 2×2000 kVA (S13-M-2000/35) | 2000 kW / 0.95 ≈ 2105 kVA → N+1 dual 2000 kVA | 84% loading after one out, nMinus1 passes Longer duration / higher power needs 2500/3150 kVA tier |
| PCS power | 2000 kW | Grid-following high-power charge/discharge | Shaving + frequency capability PCS must match grid dispatch commands |
| Storage energy | 16063 kWh usable / 17848 kWh rated | 2000 kW × 8 h; DOD 0.9 | 8 h long-duration multi-day peaking Flow / pumped / compressed-air technology caps the duration |
| Battery clusters | 83 × 215 kWh | 768 V DC · 240 series · 3.2 V cell · 280 Ah | Large-scale cluster paralleling Inter-cluster consistency / BMS balancing is the O&M focus |
| Short-circuit level | LV 36.54 kA · 50 kA breaking | IEC 60909 · Ssc 500 MVA assumption | LV breaking 1.4× · HV 3× Actual Ssc to confirm with grid company |
| Losses | 4,510,068 kWh/yr · $541,208/yr | No-load 1.12 kW + load 17.4 kW · 84% loading | Large-transformer losses are material SH15 amorphous pays back in 2.4 yr |
5 · Drawing Deep-Read
The following drawings are shown for reference (full set in the configurator “View design document”):
6 · Operation Demo (Deep-Read)
Energy flow
At valley the 35 kV grid charges the 16 MWh battery through the main transformer and PCS rectification; at peak the battery discharges through PCS inversion → main transformer → 35 kV bus (2000 kW), with 8 h support covering wider peak/valley windows.
24h operation
A typical-day curve: long-duration charge/discharge covers wider windows, shaving 2000 kW × 4 h with 8 h supporting multi-day peaking and reserve — showing the LDES time-order effect.
Economics
2000 kW × 4 h × $0.13/kWh = ≈$379,600/yr; equipment $2,314,905, EPC $2,900,000; LDES adds multi-day peaking / frequency / reserve value on top.
LCC (life-cycle cost)
At 6% discount, S13 → SH15 amorphous saves 6,920 kWh/yr (≈$830), 2.4 yr payback — the large-transformer upgrade has the best cost-benefit.
Other views (shown): Power quality & harmonics · Voltage profile · Scheme features · Environmental derating
7 · Economics & Payback
Equipment total ≈ $2,314,905, EPC ≈ $2,900,000 (incl. BESS/main transformers/distribution). Peak shaving 2000 kW × 4 h × $0.13/kWh saves ≈$379,600/yr; losses cost $541,208/yr (large-transformer heavy), SH15 amorphous saves 6,920 kWh/yr ($830/yr, 2.4 yr payback). The engine's main economic model is PV-centric; use the shaving + frequency/reserve basis for LDES value (feasibility-level).
8 · FAQ
What main transformer for long-duration storage?
How is the 8 h battery configured?
Long-duration vs short-duration storage?
How much does it save?
Why use N+1 redundancy?
What about high large-transformer losses?
Is the 35 kV short-circuit capacity enough?
What grid-code points to watch?
When does it pay back?
How are harmonics handled?
Special Considerations
- LDES connection must confirm ramp rate, primary frequency response and LVRT against the local grid code (toConfirm gridCodeNote).
- Large-transformer losses are high ($541,208/yr); the SH15 amorphous upgrade has the best cost-benefit (2.4 yr payback).
- 83 clusters in parallel — inter-cluster consistency and BMS balancing are the O&M focus (same for second-life / flow long-duration tech).
- N+1 nMinus1 passes, but confirm the actual Ssc with the grid company (36.54 kA is based on the 500 MVA assumption).
- Feasibility-level estimates; drawings are schematic, pending design-institute refinement.
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