Dry Type vs. Oil Immersed Transformer: A Comparative Guide for Electrical Procurement

 

The Core of Reliability: Making the Crucial Transformer Choice

The transformer is the silent workhorse of the electrical grid, essential for stepping up or stepping down voltage to enable efficient power transmission and utilization. When designing a new substation or upgrading an industrial facility, one of the most fundamental decisions is selecting between a Dry Type Transformer (DTT) and an Oil Immersed Transformer (OIT). This choice impacts everything from safety regulations and maintenance budgets to the physical placement of the unit.

Understanding the distinct advantages and limitations of each type is critical for ensuring long-term operational integrity and cost-effectiveness. At Degatech, we provide guidance and components for both applications, ensuring that your choice is protected by reliable switchgear solutions.

1. Dry Type Transformers (DTT): Safety and Simplicity

Dry Type Transformers are characterized by the absence of a liquid coolant. The windings are typically insulated by solid materials and cooled by air.

  • Superior Fire Safety: This is the primary advantage. Without flammable oil, DTTs have a significantly lower fire risk. They are often cast in Epoxy Resin Insulation (VPI or Cast Resin), which is self-extinguishing and non-toxic. This makes them ideal for indoor, densely populated, or high-risk locations.

    • Ideal Applications: High-rise buildings, hospitals, schools, data centers, underground substations, and chemical plants.

  • Environmental Friendliness: They pose no risk of oil spills or leaks, offering a minimal environmental footprint.

  • Maintenance: Maintenance is straightforward, involving routine cleaning and inspection, and eliminating the need for oil sampling and filtration.

  • Drawbacks: DTTs generally have higher initial costs and are typically limited in size and voltage class compared to OITs due to air's lower thermal capacity.

2. Oil Immersed Transformers (OIT): Efficiency and Endurance

Oil Immersed Transformers use mineral oil (or sometimes synthetic fluid) as both a coolant and an insulator.

  • Exceptional Cooling Efficiency: Oil is highly effective at dissipating heat, allowing OITs to be built to much larger sizes and higher voltage levels (up to EHV) without overheating. This translates to higher power ratings and better overload capacity.

  • Longer Service Life: The oil protects the cellulose insulation of the windings from moisture and oxygen, slowing down degradation and often giving OITs a longer operational life, especially in harsh outdoor conditions.

    • Ideal Applications: Large utility substations, outdoor distribution grids, generation stations, and heavy industrial plants.

  • Drawbacks: OITs require a robust containment structure (like fire walls or sumps) due to fire risk and potential environmental contamination from leaks. Maintenance is more complex, requiring regular oil analysis.

3. Protection Strategy: The Role of the Vacuum Interrupter

Regardless of the type, both DTTs and OITs are high-value assets requiring robust protection. The Vacuum Interrupter is crucial for ensuring the swift isolation of both types of transformers from damaging fault currents.

  • Speed: VCBs, powered by the Vacuum Interrupter, clear faults in milliseconds, limiting the fault current's duration and minimizing thermal and mechanical damage to the transformer windings.

  • Reliability: For OITs, which are often connected to complex overhead lines, the reliability of the VCB is paramount for managing transient overcurrents and ensuring system stability.

4. Integration with SF6 Gas Insulated Switchgear

Both transformer types must interface with switchgear. SF6 Gas Insulated Switchgear (GIS) is often chosen for its compactness, particularly in conjunction with large OITs in space-constrained substations. However, DTTs, due to their fire-safe nature, can be placed closer to non-GIS indoor switchgear, optimizing the facility layout.

Conclusion

The choice between a Dry Type Transformer and an Oil Immersed Transformer hinges on weighing long-term operational costs and safety needs against initial capacity requirements. DTTs excel in safety-critical, indoor roles, leveraging solid insulation like Epoxy Resin Insulation. OITs dominate high-power, outdoor utility applications. Both require the superior, rapid fault clearance provided by the Vacuum Interrupter within the protective switchgear. For detailed specifications on transformer protection devices and to ensure the longevity of your assets, visit chinadegatech.com.

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