SZ-2500/115kV — High-Voltage Transformer for Small Loads
Problem
Following infrastructure damage in parts of Ukraine, many small factories required fast, reliable power restoration. The sites had modest local loads but only high-voltage 110–115 kV lines nearby. Building traditional substations or major civil works would delay restart and increase cost.
Solution
We supplied SZ-2500/110kV units configured for direct 110 kV connection. Precision copper winding, vacuum drying and VPI ensured insulation reliability. The compact skid-mounted design and certified lifting points reduced transport and foundation requirements. Factory Acceptance Tests (FAT) were witnessed and commissioning followed a modular plan to speed deployment.
Result
Factories resumed production faster with reliable HV feed. The SZ solution reduced civil works and logistics complexity while offering lower operational losses vs legacy transformers.
Key advantages
Precision winding & tight air-gaps — reduces stray flux and noise; improves short-circuit robustness.
VPI + vacuum drying — factory impregnation and drying for superior insulation stability and durability.
Proven OLTC and monitoring — OLTC mechanical endurance ≥ 500,000 cycles; built-in HV CTs and optional online monitoring for predictive maintenance.
| Rated power | 2500 kVA |
| Rated voltage (HV/LV) | 110 kV / 0.415 kV |
| Vector group | YNd11 |
| Cooling | ONAN (ONAF optional) |
| Winding material | Copper |
| Active part weight | 5,000 kg |
| Oil weight | 7,950 kg |
| Tank & fittings | 8,000 kg |
| Total weight | 20,950 kg |
| Shipping weight | 15,500 kg |
| Temp rise (Top-oil / Wdg) | 55 K / 65 K (typ.) |
| OLTC | Motor-driven; mechanical endurance ≥ 500,000 cycles; electrical endurance ≥ 100,000 cycles (see TDS) |
| HV CTs | per GA (example ratios & accuracy shown in GA) |
Full Technical Table and drawing
Core & Winding
Design philosophy
The SZ-2500/110kV employs a low-loss, high-precision magnetic core and precision winding strategy to minimize no-load losses and stray flux. The core is built from high-grade cold-rolled grain-oriented (CRGO) electrical steel, with controlled lamination thickness and a step-lap joint to reduce air-gap flux leakage and magnetostriction noise.
Core construction
Material: High-grade CRGO steel, annealed and stress-relieved.
Lamination: Optimized lamination thickness and edge-treatment to minimize eddy current and inter-laminar losses.
Step-lap assembly: Step-lap joints at limb interfaces reduce flux concentration and audible noise while improving flux continuity.
Core clamping & insulation: Core clamping arranged to maintain mechanical integrity under short-circuit forces; inter-laminar insulating sheets and varnish prevent core circulating currents.
Winding technology
Conductor: Electrolytic copper conductors (standard). Aluminum available on request.
Geometry: Tight coil geometry, high turn count on the HV side with relatively small conductor diameter—engineered for small capacity/high voltage applications to meet insulation requirements in compact packages.
Banding & bracing: Each coil is mechanically banded and reinforced to withstand short-circuit mechanical stresses; radial and axial bracing methods used where required.
Insulation system: Multi-layer pressboard/paper and varnish systems; typical insulation class: Class F (with optional H-class upgrade) — final selection per TDS.
VPI & curing: Coils undergo vacuum drying and Vacuum Pressure Impregnation (VPI) to ensure full varnish penetration, remove entrapped moisture and secure mechanical bonding for long service life.
Quality controls: Winding tension, coil geometry and clamp dimensions are checked against templates; coil balance and turn count verified before impregnation.
Manufacturing & FAT (with gallery)
Manufacturing & FAT (detailed with gallery)
Manufacturing overview — traceable, repeatable
The SZ-series manufacturing line is configured for traceability and repeatability. Key production steps are documented and recorded for each unit to ensure consistent performance from core to final test.
Typical manufacturing flow
Core processing — lamination cutting, core leg & yoke stacking, step-lap assembly, annealing.
Winding — automatic winding machines, controlled tension, coil forming and insulation application.
Vacuum drying — coils baked under vacuum to reduce moisture to target ppm.
Vacuum Pressure Impregnation (VPI) — three-stage impregnation with controlled resin/temperature cycle and vacuum/pressure profile.
Assembly — core mounting, coil insertion, bracing, tank assembly and welding, installation of bushings/CTs/OLTC and auxiliary equipment.
Oil handling — vacuum degassing & filtration, controlled oil filling, sample testing per IEC 60296.
Routine & Type Testing — electrical and mechanical tests, temperature rise, impulse, short-circuit, noise measurement.
FAT — full FAT protocol execution with optional customer witness.
Quality & traceability
Material traceability: steel batch numbers, copper coil certificates, varnish/resin batch.
Process records: winding tension logs, VPI cycle logs, oven logs, assembly torque logs.
Calibration: instruments calibrated traceable to national standards; calibration certificates included in FAT pack.
FAT (Factory Acceptance Test) — scope and deliverables
Routine tests (per unit):
Ratio & polarity — within specified tolerance.
Winding DC resistance — within design tolerance.
No-load loss & current — measured at rated voltage.
Load loss & impedance — measured at rated current.
Insulation resistance — megger test per IEC.
Oil dielectric strength — per IEC 60296 (for oil units).
Visual & mechanical inspection — paint, bolts, seals.
Type tests (per design family):
Temperature-rise (hotspot and top-oil)
Lightning impulse withstand
Short-circuit withstand (3 s and peak)
Noise measurement (IEC 60076-10)
Partial discharge test (optional / if specified)
FAT pack deliverables:
FAT protocol & measured values table (CSV/PDF)
Instrument calibration certificates
Test photos (high-res) with timestamp & witness signature page
Material certificates & traceability lists
Packing & CoG drawing for transport
FAT acceptance criteria (examples)
Ratio & polarity: within drawing tolerance (e.g., ±0.5%).
No-load loss: not to exceed TDS stated value (± specified tolerance).
Load loss & impedance: measured values must be within TDS/contract tolerance.
Temperature rise: hotspot and top-oil within type test limits.
(Exact numeric tolerances per contract/TDS — replace with project values.)
Installation, Packing & Logistics
Operation & Maintenance (O&M)
FAQ
Q: Is SZ-2500/110kV suitable for tropical/coastal environments?
A: Yes — tropical epoxy painting, silica gel breathers and corrosion protection are available as standard options.
Q: What is OLTC endurance?
A: Mechanical endurance ≥ 500,000 cycles; electrical endurance ≥ 100,000 cycles at rated current (≤1000 A). See OLTC datasheet.
CTA & Contact Block
Request a Quote
— RFQ form: Company / Contact / Country / Product / Model / kVA / Voltage / Quantity / Drawings upload / Decision date.
— RFQ form: Company / Contact / Country / Product / Model / kVA / Voltage / Quantity / Drawings upload / Decision date.
Technical Contact: Orin Fang
— orin.fang@cnyge.com
— orin.fang@cnyge.com
— WhatsApp: +86-15305704090
