In modern power systems, thermal management of transformers is critical to ensure stable operation and prolong equipment lifespan. As power load demands increase, efficient and safe cooling has become a key concern in transformer design and maintenance. The two most common cooling methods are dry-type (air-cooled) and oil-immersed (liquid-cooled) transformers. This article compares their performance from several perspectives.

Cooling Principles

1.Dry-Type Transformers

Dry-type transformers rely on natural air convection or forced-air cooling. Without a liquid medium, heat is transferred from the core and windings to the external casing, and dissipated by surrounding air. Some models include fans to increase airflow and enhance cooling efficiency.

2.Oil-Immersed Transformers

Oil-immersed transformers use insulating oil as a cooling medium. Heat generated inside the transformer is transferred to the oil, which rises and circulates, releasing heat through external radiators. Some systems include forced oil circulation with pumps and fans to further improve cooling.

Cooling Efficiency

1.Thermal Conductivity

Insulating oil has much higher thermal conductivity than air, allowing oil-immersed transformers to dissipate heat more quickly. Therefore, they perform better under high loads and continuous operation conditions.

2.Environmental Adaptability

Dry-type transformers are more affected by ambient temperature and ventilation conditions, with cooling efficiency dropping in summer or enclosed spaces. Oil-immersed transformers offer better adaptability and stability in extreme environments.

Operational Costs

1.Energy and Consumables

Dry-type transformers have lower operational costs, with no need for oil changes and minimal energy use for fans. Oil-immersed transformers require regular oil checks and replacements, plus power for pumps and fans, leading to higher operating costs.

2.Initial Investment and Service Life

Oil-immersed transformers have a more complex structure and higher upfront cost. However, their superior cooling contributes to longer service life and lower failure rates, potentially balancing long-term investment.

Safety Considerations

1.Fire Hazards

Dry-type transformers use no flammable materials, making them ideal for high-rise buildings, subways, and malls. Oil-immersed transformers require strict fire prevention measures due to their use of flammable oil.

2.Environmental and Leakage Risks

Dry-type transformers are more environmentally friendly and pose no leakage risk. Oil-immersed models require proper management to prevent oil spills and environmental contamination.

Maintenance Requirements

1.Routine Inspections

Dry-type transformers require minimal maintenance, mainly checking fan operation and dust levels. Oil-immersed transformers need regular monitoring of oil levels, quality, electrical performance, and cooling system functionality.

2.Operational Complexity

Dry-type transformers are suitable for small substations or unattended installations. Oil-immersed transformers are better for industrial or main grid stations and require skilled personnel.

Application Recommendations

Comparison Item	Dry-Type Transformer	Oil-Immersed Transformer
Cooling Efficiency	Moderate, air-dependent	High, suitable for heavy load
Operational Cost	Low, easy maintenance	High, requires oil and system upkeep
Safety	High, fire-safe and eco-friendly	Needs fire control, leakage risk
Recommended Use	Indoor, commercial, small substations	Industrial, large-scale power systems

Purchase Advice

• Dry-type transformers are ideal for locations prioritizing safety, environmental protection, and low maintenance—such as hospitals, malls, and public transit facilities.
• Oil-immersed transformers are suitable for high-power, long-duration operations, especially in harsh environments with demanding cooling requirements.

When selecting a transformer, users should consider the operational environment, load conditions, and available maintenance resources to choose the most suitable cooling method.

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