Analysis of Operation Modes for Dry-Type Transformers

　　Dry-type transformers are widely used in commercial buildings, data centers, industrial plants, and other applications due to their oil-free, fire-resistant, and environmentally friendly characteristics. Their operation modes must be optimized based on equipment specifications, load requirements, and environmental conditions to ensure safety and cost-effectiveness. Below is an analysis from four dimensions: operation modes, load management, environmental control, and maintenance strategies.

　　I. Classification of Operation Modes

　　Continuous Long-Term Operation

　　Application Scenarios: Data centers, hospitals, airports, and other facilities with high demands for uninterrupted power supply.

　　Key Points:

　　Ensure the ambient temperature does not exceed 40°C (IEC standard) and maintain good ventilation.

　　Install a temperature control system (e.g., forced air cooling via fans) that activates when winding temperature exceeds a threshold (e.g., 110°C).

　　Regularly monitor insulation resistance (recommended every six months) to ensure it is ≥100 MΩ (at 20°C).

　　Intermittent Operation

　　Application Scenarios: Factory production lines, shopping mall lighting, and other scenarios with fluctuating loads.

　　Key Points:

　　Avoid frequent startups and shutdowns (recommended interval of ≥5 minutes between startups) to reduce thermal stress on insulation.

　　Equip with an intelligent control system that automatically adjusts operation modes based on load changes (e.g., switching to natural cooling under light loads).

　　Emergency Standby Operation

　　Application Scenarios: Backup power systems for fire protection equipment, emergency lighting, etc.

　　Key Points:

　　Conduct monthly no-load test runs (≥15 minutes) to check for abnormal temperature rises and sounds.

　　Ensure insulation materials (e.g., epoxy resin) are not aged (no cracks or discoloration).

　　II. Load Management Strategies

　　Load Rate Control

　　Optimal Operating Range: 50%–70% of rated load, where efficiency is highest (approximately 98%–99%).

　　Overload Limitations:

　　Short-term overload (e.g., 1.2 times rated load) is permissible for up to 2 hours, but temperature rise must be monitored (core temperature ≤155°C).

　　Prolonged overload shortens insulation life (life halves for every 8°C increase, according to Montsinger's Rule).

　　Three-Phase Balance

　　The unbalance degree of single-phase loads should not exceed 10%; otherwise, local overheating may occur (e.g., winding temperature in one phase may rise by over 20°C).

　　Install a three-phase current monitoring device for real-time alarming of unbalance.

　　III. Environmental Control Requirements

　　Temperature and Humidity

　　Temperature: The operating ambient temperature should not exceed 40°C; otherwise, derating is required (e.g., 5% derating for 40°C–50°C).

　　Humidity: Relative humidity should not exceed 90% (no condensation). In high-humidity environments, dehumidification devices should be installed.

　　Ventilation and Dust Control

　　Ventilation volume should meet ≥5 m³/min·kW (for natural cooling) or ≥8 m³/min·kW (for forced air cooling).

　　The dust protection rating should be ≥IP2X to prevent metallic particles from entering and causing partial discharge.

　　IV. Maintenance and Monitoring Strategies

　　Regular Inspections

　　Frequency: Monthly checks for physical condition (no abnormal sounds or odors) and tightness of connection bolts (torque values should meet standards).

　　Infrared Thermography: Conduct quarterly checks for hot spots; abnormal temperature rises (e.g., exceeding ambient temperature by 40°C) require immediate investigation.

　　Preventive Testing

　　Insulation Resistance Test: Conduct annually using a 2500V megohmmeter; results should be ≥1000 MΩ (at 20°C).

　　Partial Discharge Test: Conduct every three years; discharge magnitude should be ≤5 pC (at 1.1 times rated voltage).

　　V. Handling of Abnormal Conditions

　　Abnormal Temperature Rise

　　Immediately shut down the transformer to inspect fans, ventilation ducts for blockages, or check for overload.

　　Example: A data center experienced winding temperatures reaching 180°C due to fan failure, resulting in carbonization of insulation materials and eventual replacement of the entire transformer.

　　Abnormal Sounds

　　Increased humming may indicate loose iron cores, requiring tightening of clamps.

　　Cracking sounds may indicate partial discharge, necessitating immediate power shutdown and inspection.

　　Conclusion

　　The operation modes of dry-type transformers must be tailored to load characteristics, environmental conditions, and maintenance capabilities. By implementing load rate control, environmental monitoring, and preventive maintenance measures, the service life of the equipment can be significantly extended (design life typically ≥30 years). It is recommended that users establish a digital operation and maintenance platform to collect real-time data on temperature, load, etc., enabling predictive maintenance.