Selecting the right transformer is not just a technical decision—it directly impacts safety, reliability, and lifecycle costs. Many project owners face the same question: Should I choose a dry-type transformer or an oil-immersed transformer?
At TAILI ELECTRIC, we've supported countless projects worldwide, and we know that making the wrong choice can lead to higher maintenance costs, safety risks, or even project delays. This guide highlights the key factors you must know before deciding.
1. Safety First
Dry-Type Transformer: Fire-resistant, non-flammable, suitable for crowded indoor spaces such as hospitals, malls, and high-rise buildings.
Oil-Immersed Transformer: Uses mineral oil that may pose fire hazards if not managed properly. Fire barriers and oil containment pits are usually required.
Avoid this mistake: Don't install oil-immersed transformers in basements or enclosed areas without proper fire safety design.
2. Performance Comparison
Here's a chart of dry-type and oil-immersed transformers compare provided by Taili Electric.
| Key Parameter | Dry-Type Transformer | Oil-Immersed Transformer |
| Capacity Range | ≤ 2500 kVA | From small to several hundred MVA |
| Voltage Level | 6–35 kV | Covers 6–220 kV and above |
| Efficiency | 97–98% | 98–99% |
| Losses | Slightly higher copper losses | Lower losses, better cooling |
| Noise Level | Low (≈ 50–60 dB) | Medium (≈ 60–70 dB) |
| Service Life | 20–30 years | 25–35 years |
| Fire Safety | Excellent, flame-retardant | Moderate, oil is flammable |
| Maintenance | Low, almost maintenance-free | Higher, requires oil monitoring |
| Installation | Best for indoor use | Best for outdoor/large capacity |
| Cost | Higher upfront investment | Lower purchase, higher O&M cost |
3. Visual Performance Overview
Dry-Type excels in Safety, Fire Resistance, Maintenance.
Oil-Immersed leads in Capacity, Efficiency, Initial Cost.
4. Application Scenarios
Dry-Type Transformers:
-High-rise buildings, hospitals, airports, subways, shopping malls.
-Indoor projects where fire safety and environmental concerns are critical.
Oil-Immersed Transformers :
- Outdoor substations, heavy industry, utility networks.
- Projects requiring large capacity and high efficiency.
5. Cost Analysis
- Dry-Type: Higher initial cost but reduced maintenance, better lifecycle value in indoor/public applications.
- Oil-Immersed: Lower purchase cost, but consider expenses for oil monitoring, fire protection, and periodic servicing.
6. Bushing & Connection Design
Most dry-type transformers typically adopt epoxy resin insulators combined with copper bars for outgoing connections, ensuring reliable mechanical strength and easy integration with switchgear or bus ducts.
In contrast, oil-immersed transformers generally employ porcelain bushings, particularly on the high-voltage side, while the low-voltage side may use either copper bars or bushings depending on the installation requirements.
7. Quick Decision Guide
Choose Dry-Type Transformer if:
✓ Your project is indoors
✓ Fire safety is critical
✓ People density is high (schools, hospitals, airports)
Choose Oil-Immersed Transformer if:
✓ Your project is outdoors
✓ Capacity demand is high
✓ Long-term efficiency is top priority
The right transformer is not always the cheapest—it's the one that ensures safety, reliability, and long-term performance.
With over 30 years of expertise, TAILI ELECTRIC designs and manufactures both dry-type and oil-immersed transformers under IEC standards. Our company is certified with three ISO quality management systems, our products are backed by CE certificates and test reports, and our oil-immersed transformers are type-tested by ASTA.
Whether you are building a city skyscraper or a utility substation, we can help you avoid costly mistakes and select the solution that truly fits your needs.
TAILI ELECTRIC – Powering a Safer World
