SFZ-25000/63-35 — 25 MVA (25,000 kVA) 63/35 kV OLTC Power Transformer | YUANGUANG (YGT)

Short catalog card (for product list)

Model: SFZ-25000/63-35

Rated power: 25,000 kVA (ONAF); 16,600 kVA (ONAN)

Rated voltage: HV 63 kV / LV 35 kV

Tap changer: 21-tap OLTC (motor-driven) — ±10 × 1.5%

Cooling: ONAF (fans) — ONAF capacity 25,000 kVA; ONAN 16,600 kVA

Vector group: YNd11

Winding: Copper (HV & LV) — interleaved / continuous design

Core: Grain-oriented silicon steel (CRGO) — step-lap / epoxy bonded

Key performance: No-load 37.5 kW; Load loss 140 kW; Impedance 11.8%; Top-oil rise 55°C; Winding rise 60°C

Standards: IEC60076 (parts 1,2,3,5,10)

Origin: Zhejiang, China — Supply ability: 5,000 sets/year

YUANGUANG’s SFZ-25000/63-35 is a utility-grade 25 MVA (25,000 kVA) OLTC power transformer engineered for primary substations, power plants and demanding EPC projects. Designed around a high-permeability CRGO core with precise step-lap joints and epoxy-bonded laminations, the SFZ-25000 delivers low no-load loss and suppressed audible noise while providing the mechanical rigidity and thermal performance required for heavy duty operation.

The transformer features an interleaved-continuous HV winding and a zig-zag oil-guide structure that forces oil circulation into otherwise stagnant zones — reducing hotspot rise and extending insulation life. A motor-driven 21-tap OLTC (±10 × 1.5% tap range) enables accurate on-load voltage regulation for grid stability under variable loading. The SFZ series is vacuum-dried and VPI-impregnated to guarantee complete varnish penetration and excellent moisture resistance — a decisive benefit in coastal or humid climates.

Performance targets were validated in factory acceptance tests: no-load loss 37.5 kW, load loss 140 kW (total losses 177.5 kW), short-circuit impedance 11.8% and PD / noise control consistent with utility requirements. The unit complies with the IEC60076 family and ships with full FAT documentation, calibration certificates and certified CoG and lifting drawings for safe logistics and rapid site installation

High capacity with flexible cooling — ONAF rating 25,000 kVA (ONAN 16,600 kVA) for robust overload performance.

Low losses — lower OPEX — optimization yields significantly reduced no-load losses vs generic designs.

Low partial discharge & low noise — design and manufacturing controls keep PD and acoustic emissions within strict limits.

Superior thermal control — zig-zag oil guide and interleaved winding reduce hotspot and improve thermal uniformity.

Robust OLTC — 21-tap motorized OLTC for precise on-load voltage regulation.

Strong mechanical design — epoxy bonded core, bracing plates and impregnation to withstand transport and short-circuit forces.

Turnkey deliverables — FAT pack, traceability certificates, CoG & certified lifting plan, easy commissioning.

Packing: accessories in seaworthy wooden cases; silica gel & anticorrosion applied. Main tank shipped naked for oversize shipment, or crated to buyer instruction.

Logistics: Certified CoG and lifting plan; low-loader shipment and port handling instructions.

Site readiness: Concrete pad and earthing per GA; recommended skid mounting and crane lift using specified sling angles.

Routine: oil sampling & dielectric test, silica gel replacement, fan & radiator checks, OLTC inspection and contact check.

Periodic: thermography inspection, oil dissolved gas analysis (DGA) for large units, OLTC maintenance per cycles.

O&M documents: included: manual, fault tree, FAT summary and commissioning checklist.

No-load loss: 37.5 kW

Load loss: 140 kW

Impedance: 11.8%

Top-oil / winding rise: 55 °C / 60 °C

PD & noise: PD < 80 pC (design); noise ≤ 58 dB(A) measured per FAT

Full numeric tables and test certificates available in the FAT pack.