Power transformers are categorized by various criteria, but common types include oil-immersed, dry-type, and box-type substations. Today, we’ll explore dry-type transformers—their cooling/insulation mechanics, advantages/disadvantages, and key differences from oil-immersed counterparts.
How Dry-Type Transformers Cool and Insulate
Dry-type transformers stand out because their cores and windings aren’t submerged in insulating oil. So how do they manage heat and electrical isolation?Cooling: They use two methods:
- Natural Air Cooling (AN): Under rated capacity, heat dissipates via natural air convection—no extra equipment needed for long-term continuous operation.
- Forced Air Cooling (AF): When ambient temperatures hit ~80°C, temperature-controlled fans activate to boost airflow. This dramatically improves heat dissipation, enabling reliable performance in overloads or high-heat environments.
Insulation: Epoxy resin is the primary material, with specialized manufacturing processes to optimize performance. Common designs include epoxy quartz sand vacuum casting, epoxy alkali-free glass fiber reinforced vacuum casting, and alkali-free glass fiber wound impregnation.
Advantages of Dry-Type Transformers
- Superior Safety: No flammable oil eliminates fire/explosion risks—critical for sensitive spaces. Strong electrical insulation also prevents leaks or short circuits.
- Eco-Friendly: No oil-based cooling/insulation means zero pollution, aligning with sustainability goals.
- Energy Efficient: Optimized coil structures, high-performance insulation, and advanced manufacturing reduce losses, keeping operational energy use low.
- Reliable Longevity: Advanced materials and processes extend service life with a low failure rate, ensuring stable power system performance.
Disadvantages of Dry-Type Transformers
- Moisture/Dust Sensitivity: Poor resistance to humidity/particulates—may require protective covers or dedicated rooms in harsh settings to preserve insulation.
- Limited Harsh Environment Use: Primarily for indoor use. Outdoors, they need extra protection (e.g., weatherproof enclosures) to maintain function and lifespan.
- High Material Costs: Depend on expensive, high-thermal-conductivity insulation (e.g., treated epoxy resin), raising production expenses.
- Difficult Repairs: Damaged coils are nearly unfixable locally—usually requiring full replacement, increasing downtime and cost.
Key Differences from Oil-Immersed Transformers
- Visual Design: Oil-immersed transformers have metal casings hiding cores/windings; dry-type models leave cores and windings exposed.
- Cooling/Insulation Medium: Oil-immersed units use insulating oil for both cooling and insulation—dry-type relies on air.
- Size & Structure: Dry-type units are smaller/lighter (no oil tank) for easier transport. Their windings/core are wrapped in multi-layer insulation, while cores use laminated silicon steel to minimize flux loss.
- Application Scenarios: Dry-type excel indoors—ideal for fire/explosion-sensitive spaces (hospitals, malls) due to zero oil risk. Oil-immersed are preferred outdoors for large grids/substations: better heat dissipation, higher load/voltage tolerance, and suitability for rough outdoor conditions.