Dry-Type vs Oil-Immersed Transformers: Export Selection Guide for EPC Buyers

Introduction

Dry-type and oil-immersed transformers solve different project problems. The best choice depends on installation location, fire strategy, efficiency target, environmental condition, maintenance capability and local authority approval.

This guide is written for overseas buyers, EPC contractors, consultants and local utility reviewers. It uses IEC 60076, IEC 60076-11 for dry-type transformers, IEC 60076-1 for oil-immersed transformers and local fire or utility requirements as the main technical language, with the final acceptance route defined by the project specification and local approval process.

1. Buyer Decision Points

Decision point	What to check before RFQ
Installation location	Indoor building, outdoor yard, kiosk or containerized substation
Fire strategy	Oil containment, fire wall or dry-type low-fire-load requirement
Cooling	Room airflow, outdoor radiator space or fan-assisted operation
Maintenance	Oil testing versus dry-type cleaning and inspection
Lifecycle cost	Purchase price, losses, maintenance and downtime risk

2. RFQ Data to Provide

• Rated kVA, voltage ratio, frequency and vector group.
• Indoor/outdoor installation and fire authority requirement.
• Loss guarantee and efficiency target.
• Ambient temperature, altitude and humidity/corrosion level.
• Enclosure, cable box and monitoring requirements.
• Routine test, type test reference and FAT requirement.

3. Supplier Documents to Request

• Datasheet and compliance matrix.
• General arrangement and foundation drawing.
• Oil quantity or dry-type insulation/PD data.
• Temperature monitoring wiring diagram.
• Installation and maintenance manual.
• Routine test report and FAT checklist.

4. Engineering Review Checklist

Review item	Why it matters
Fire risk	Often drives indoor dry-type selection
Cooling margin	Both types need site-specific thermal review
Maintenance access	Must match owner capability
Efficiency	Losses affect lifecycle cost
Authority approval	Local rules may restrict transformer type in buildings

5. Reference Standards and Local Approval

Use IEC 60076 for transformer requirements and IEC 60076-11 for dry-type units. Local building, fire and utility requirements should be checked before final selection.

Buyer Recommendation

Select transformer type from site risk and operating requirements, not from habit. For export projects, ask for fire, cooling, loss and maintenance documents before comparing price.