A dry-type transformer is a power transformer that does not use liquid cooling media. Its windings and iron core are directly exposed to the air, relying on air convection for cooling. Compared with oil-immersed transformers, dry-type transformers have the following prominent characteristics:
- Oil-Free Design: Does not use flammable insulating oil, eliminating the risks of oil leakage and fire, and improving safety.
- Environmental Performance: Contains no oil-based substances, avoiding soil and water pollution, and complying with modern environmental requirements.
- Easy Maintenance: No need for regular oil level and quality checks, reducing maintenance workload and costs.
- Flexible Installation: Relatively small in size and light in weight, allowing more flexible selection of installation locations.
- Strong Overload Capacity: Possesses strong short-term overload capacity to adapt to load fluctuations.
The primary factor determining whether a dry-type transformer can be used outdoors is its protection level (IP rating). Outdoor environments are subject to erosion by various natural factors such as rain, dust, and salt spray, thus requiring a high protection level:
- IP23: Protected against vertical falling water and water spray at a certain angle, suitable for outdoor environments with canopies.
- IP54: Dustproof and splash-proof, suitable for general outdoor environments.
- IP65: Fully dustproof and protected against water jets, suitable for harsh outdoor environments.
Modern dry-type transformers can achieve high protection levels through special design and manufacturing processes, meeting outdoor usage requirements.
Outdoor environments have large temperature variations, so dry-type transformers need to adapt to:
- High-Temperature Environments: In hot regions, transformers require good heat dissipation design, usually adopting forced air cooling (AN/AF) to enhance heat dissipation capacity.
- Low-Temperature Environments: In cold regions, it is necessary to consider the low-temperature brittleness of materials and changes in insulation performance, and select insulation materials suitable for low-temperature environments.
- Day-Night Temperature Differences: Frequent temperature changes may cause material expansion and contraction, requiring the selection of materials with good thermal stability.
In outdoor environments, transformers face:
- Salt Spray Corrosion: Coastal areas require salt spray protection measures, such as using stainless steel fasteners and special coatings.
- Industrial Pollution: Industrial areas need to consider the impact of acid rain and chemical corrosion.
- Ultraviolet Aging: Direct sunlight can cause aging of plastic parts and coatings, requiring the selection of UV-resistant materials.
Outdoor environments have large humidity changes, which are prone to condensation, potentially leading to:
- Reduced insulation performance
- Rust of metal components
- Risk of electrical short circuits
Solutions include:
- Built-in heaters to maintain internal dryness.
- Adoption of moisture-proof insulation materials.
- Design of reasonable ventilation structures.
To adapt to outdoor environments, dry-type transformers usually require the following special designs:
- Use stainless steel or galvanized steel sheet enclosures to enhance corrosion resistance.
- Design inclined top covers to prevent water accumulation.
- Add ventilation louvers to ensure heat dissipation while preventing rainwater ingress.
- Use insulation materials with better weather resistance.
- Add moisture-proof coatings.
- Adopt the Vacuum Pressure Impregnation (VPI) process to improve moisture-proof performance.
- Increase the number or power of fans.
- Design reasonable air ducts.
- Consider water-cooled auxiliary systems in high-temperature environments.
- Elevate the installation foundation to prevent water immersion.
- Consider shockproof measures.
- Design space for convenient maintenance operations.
- No need to construct a dedicated transformer room, saving civil engineering costs.
- Flexible installation location selection, allowing proximity to load centers.
- No fire risk, especially suitable for densely populated areas.
- Simple maintenance and low life-cycle costs.
- Relatively small capacity, with potential restrictions on large-capacity applications.
- Higher initial investment cost than oil-immersed transformers.
- Performance may be affected in extreme environments.
- Higher requirements for noise control.
- Urban Power Distribution Networks: Installed in densely populated areas such as residential districts and commercial areas.
- Industrial Plants: Places with explosion-proof requirements such as chemical and mining industries.
- Infrastructure: Transportation facilities such as tunnels, bridges, and subways.
- New Energy Field: Renewable energy projects such as photovoltaic power stations and wind farms.
- Temporary Power Supply: Temporary power needs for construction sites, event venues, etc.
To ensure the long-term reliable operation of outdoor dry-type transformers, the following recommendations are proposed:
- Check for corrosion and deformation of the enclosure.
- Clean dust and debris from ventilation openings.
- Inspect for loose electrical connections.
- Monitor operating temperature to ensure it does not exceed limits.
- Check the effectiveness of moisture-proof measures during the rainy season.
- Pay attention to antifreeze measures in winter.
- Regularly conduct insulation resistance tests.
- Inspect the operating status of the cooling system.
- Perform professional cleaning and maintenance when necessary.
With technological progress, outdoor dry-type transformers will show the following development trends:
- Intelligence: Integrate sensors for temperature, humidity, etc., to achieve remote monitoring.
- High Reliability: The application of new materials and processes will improve product lifespan.
- Environmental Friendliness: More environmentally friendly materials and recyclable designs.
- Modularization: Modular design for easy installation and maintenance.
- High Efficiency and Energy Saving: Lower loss design to improve energy efficiency levels.
Dry-type transformers can be fully used in outdoor environments, but it is necessary to select products with appropriate protection levels and special designs according to specific environmental conditions. Through reasonable product selection, correct installation, and regular maintenance, outdoor dry-type transformers can provide safe and reliable power supply.
