When engineers and procurement teams buy power transformer equipment for an overseas project, the decision rarely comes down to price alone. Voltage ratio, impedance, cooling class, efficiency regulation, and site conditions all determine whether a unit performs for 25 years or becomes a maintenance liability. This guide explains how to specify and source transformers from a manufacturer that builds to IEC, IEEE, and GB standards — and shows how FIJ TECH approaches real export projects.
FIJ TECH is a transformer manufacturer supplying oil immersed and dry type units from 30kVA to 31500kVA, at 6kV, 10kV, 11kV, 20kV, 33kV, and 35kV, in both 50Hz and 60Hz designs. Whether you are an EPC contractor, a utility buyer, or an electrical engineer preparing a tender package, the sections below cover the technical checks that protect your project schedule.
What to Confirm Before You Buy a Power Transformer
Most procurement errors trace back to an incomplete specification. Before requesting quotations, confirm the primary and secondary voltage, rated capacity, vector group, impedance voltage, tapping range, cooling method, and the applicable efficiency standard for the destination market.
Efficiency requirements differ by region. China applies GB 20052-2020, the European Union enforces EcoDesign Tier 2, and the United States follows DOE 2016. A transformer that meets one standard may not satisfy another, so state the target regulation in your inquiry. Design and testing should reference IEC 60076 for power transformers, IEC 60076-11 for dry type units, and IEEE C57.12.00 where North American practice applies.
- Voltage levels: 6kV, 10kV, 11kV, 20kV, 33kV, 35kV
- Capacity range: 30kVA to 2500kVA standard; up to 31500kVA custom
- Frequency: 50Hz or 60Hz
- Cooling: ONAN, ONAF, AN, AF
- Quality system: ISO 9001:2015; CE marking available
You can review the full product catalog to match a standard model to your load calculation, or send a specification for a custom build.
Dry Type vs Oil Immersed: Choosing the Right Unit
The choice between cast resin dry type and oil immersed transformers is usually driven by installation environment, fire safety, and maintenance access. Dry type units suit indoor substations, basements, and commercial buildings where oil containment is impractical. Oil immersed units remain the economic choice for outdoor distribution, higher capacities, and harsh ambient conditions.
For indoor and fire-sensitive locations, browse the dry transformer range built to IEC 60076-11 with F-class or H-class insulation. For outdoor distribution networks, the oil transformer range covers standard and energy-efficient designs, including amorphous alloy cores.
| Parameter | Dry Type (Cast Resin) | Oil Immersed |
|---|---|---|
| Typical capacity | 30–2500kVA | 30–31500kVA |
| Cooling | AN / AF | ONAN / ONAF |
| Installation | Indoor, basement, no oil pit | Outdoor or indoor with containment |
| Reference standard | IEC 60076-11 | IEC 60076, GB 1094 |
One frequently specified oil unit is the SH15 Amorphous Alloy Oil Immersed Power Transformer, which reduces no-load loss compared with conventional silicon steel cores — useful where utilities penalise standing losses.
Matching Transformers with Low Voltage Switchgear
A transformer is only one half of a substation. The low voltage side must coordinate with switchgear rated for the transformer’s secondary fault current, and the protection settings must reflect the impedance voltage on the nameplate.
For compact substations and commercial distribution rooms, the GGD Low Voltage Distribution Cabinet is commonly paired with both dry type and oil immersed transformers. Compact substation assemblies can be designed to GB/T 17467 where an integrated package is preferred.
- Confirm switchgear breaking capacity exceeds prospective short-circuit current
- Verify cable and busbar sizing against transformer full-load current
- Check protection relay curves against transformer inrush
- Confirm IP rating suits the room environment
Case Study: 35kV SCB14 Dry Type Transformer, Saudi Arabia
A commercial complex in Saudi Arabia required a 35kV to 0.4kV step-down transformer for an indoor basement substation. The available footprint was tight, and local fire safety rules made oil containment difficult to justify. The project team needed a unit that could be installed indoors without an oil pit or fire suppression upgrade.
FIJ TECH supplied an SCB14-2500/35 cast resin dry type transformer rated 2500kVA, 35kV/0.4kV, with F-class insulation and an IP31 enclosure. The design was verified to IEC 60076-11, with CE marking and ISO 9001:2015 quality management behind the manufacturing process. Testing covered routine electrical tests before shipment.
The customer reported: “The dry type transformer fits our basement substation perfectly. No oil containment needed.” For projects with similar constraints — hospitals, data centres, tunnels, and high-rise buildings — cast resin dry type units remove the oil handling and fire risk variables from the design.
Voltage Drop & Short-Circuit Impedance Check
Impedance voltage (uk%) appears on every transformer nameplate, and it directly affects both protection coordination and voltage regulation. A mismatch here is one of the most common causes of nuisance tripping or failed motor starting on site.
- Verify transformer impedance voltage (uk%) matches switchgear breaking capacity.
- Typical 10kV distribution transformer: uk = 4%.
- Calculate voltage drop under load: ΔU = β × uk × (cosφ + sinφ × tanθ).
- Ensure voltage drop at full load stays below 5% at motor terminals.
In the formula, β is the load factor, cosφ is the load power factor, and tanθ relates to the transformer’s reactance-to-resistance ratio. For a 10kV transformer with uk = 4% at full load and a power factor of 0.8, the calculated drop should be checked against the allowable limit at the most remote motor. If the drop exceeds 5%, consider a larger capacity unit, a lower impedance design, or cable upsizing.
Higher impedance limits fault current but increases voltage drop. Lower impedance improves regulation but raises the duty on downstream switchgear. The correct value depends on the network, which is why FIJ TECH reviews impedance, vector group, and tap range against your single-line diagram before confirming an order.
Certifications and Compliance for Export Projects
Export buyers should confirm that the manufacturer’s quality system and product testing align with the standards named in the tender. FIJ TECH works to ISO 9001:2015, IEC 60076, IEC 60076-11, IEEE C57.12.00, GB 1094, and GB/T 17467 for compact substations. CE marking is available for European-conformity requirements, and VDE can be referenced as a project basis where specified.
- Routine tests: ratio, polarity, resistance, impedance, insulation, loss measurement
- Type tests available on request for project approval
- Documentation package: test reports, nameplate data, outline drawings, O&M manual
- Packing and marking per destination customs requirements
How to Request a Quote
To get an accurate quotation, send your capacity, voltage ratio, frequency, vector group, impedance, cooling method, installation environment, and the efficiency standard you must meet. If you have a single-line diagram or tender specification, include it — the engineering team will confirm the closest standard model or propose a custom design.
Ready to buy power transformer equipment for your next project? Visit FIJ TECH, review the transformer range, and submit your parameters for a technical response and quotation.
Related reading: oil transformer articles and dry type transformer articles.