Dry-type transformers for small substations

   Dry-type transformers for small substations are power transformers that use air or solid insulating materials (such as epoxy resin) for cooling and insulation, and they have the characteristics of safety, environmental protection, and low maintenance. The following is the collation of its core information:

 I. Main Characteristics

1. **Oil-free Design**

   - Adopt epoxy resin casting or impregnation insulation, avoiding the risks of oil leakage and fire of oil-immersed transformers.

   - Suitable for indoor and densely populated areas (such as residential communities and commercial centers).

2. **High Efficiency and Energy Conservation**

   - Low losses (the no-load loss is about 30% lower than that of oil-immersed transformers), meeting national energy efficiency standards (such as GB 20052).

3. **Low Noise**

   - The iron core is made of high-quality silicon steel sheets and advanced processes, and the operating noise is usually lower than 60dB.

4. **Moisture-proof and Anti-fouling**

   - The epoxy resin casing has a protection level of IP20-IP54, adapting to humid and dusty environments.

 II. Application Scenarios

- **Residential Communities**: 10kV/0.4kV power distribution, with a capacity usually ranging from 200 to 1600kVA.

- **Commercial Buildings**: Power supply systems of shopping malls, hospitals, and office buildings.

- **Industrial Field**: Step-down, isolation, or special power supply requirements within factories.

- **Rail Transit**: Auxiliary power supply for subways and high-speed railway stations.

 III. Key Points for Model Selection

1. **Capacity Selection**

   - Calculate according to the load current, formula:  with a reserved overload margin of 10%-20%.

   - Example: If the load current is 100A and the voltage is 10kV, then the capacity is approximately  and 2000kVA can be selected.

2. **Voltage Levels**

   - Common inputs: 10kV, 20kV; outputs: 0.4kV (three-phase) or 0.23kV (single-phase).

3. **Cooling Methods**

   - **Natural Air Cooling (AN)**: No additional equipment is required, suitable for light loads.

   - **Forced Air Cooling (AF)**: Cooling through fans, which can be overloaded by 30%-50% for a short time.

4. **Protection Levels**

   - IP20: Protects against finger touch; IP30: Protects against vertical water droplets; IP54: Protects against dust and water jets.

 IV. Maintenance and Fault Handling

1. **Daily Maintenance**

   - **Cleaning**: Blow off the surface dust with compressed air every six months.

   - **Temperature Monitoring**: The temperature rise of the winding does not exceed 100K (epoxy resin), and the hot spot temperature ≤ 130°C.

   - **Insulation Test**: Use a 2500V megohmmeter, and the insulation resistance ≥ 100MΩ (between windings and to the ground).

2. **Common Faults and Countermeasures**

 V. Safety Precautions

1. **Overload Protection**: Configure a temperature controller (such as the BWD3K series), which will automatically alarm or trip when the temperature exceeds the limit.

2. **Heat Dissipation Design**: The transformer room needs to have good ventilation, and the temperature difference between the air inlet and the air outlet ≤ 15°C.

3. **Grounding Requirements**: The neutral point and the casing must be reliably grounded, and the grounding resistance ≤ 4Ω.

 Summary

Dry-type transformers have become the mainstream choice for small substations due to their safe and environmentally friendly characteristics. When selecting a model, it is necessary to combine the load requirements, environmental conditions, and maintenance costs. During operation, it is necessary to focus on monitoring the temperature and insulation status. In case of complex problems (such as winding faults), it is recommended to contact WanKong or a professional maintenance team for handling.