The working temperature of dry-type transformers is influenced by the thermal endurance grades of insulating materials, with core parameters and operational requirements as follows:

　　I. Thermal Endurance Grades of Insulating Materials and Temperature Limits

　　The insulating materials in dry-type transformers are classified into multiple thermal endurance grades, each corresponding to different maximum operating temperatures and temperature rise limits:

　　Grade A: Maximum operating temperature of 105℃, maximum temperature rise < 60K

　　Grade E: Maximum operating temperature of 120℃, maximum temperature rise < 75K

　　Grade B: Maximum operating temperature of 130℃, maximum temperature rise < 80K

　　Grade F: Maximum operating temperature of 155℃, maximum temperature rise < 100K

　　Grade H: Maximum operating temperature of 180℃, maximum temperature rise < 125K

　　Grade C: Maximum operating temperature of 220℃, maximum temperature rise < 150K

　　Mainstream Choices: Modern dry-type transformers predominantly utilize Grade F or Grade H insulating materials, with maximum allowable temperatures typically at 155℃ (Grade F) or 180℃ (Grade H). Exceeding these temperatures accelerates insulation aging, posing risks of short circuits or fires.

　　II. Normal Operating Temperature Range

　　The actual operating temperature of dry-type transformers is influenced by load, cooling methods, and environmental conditions, generally ranging from 80℃ to 120℃:

　　Load Impact: Higher load factors result in faster temperature rises. For instance, temperatures may approach insulation limits under full-load operation.

　　Cooling Methods: Naturally cooled (AN) transformers exhibit higher temperatures, while forced-air cooling (AF) reduces temperatures by 10-20℃.

　　Environmental Conditions: Elevated temperatures may occur in summer or with poor ventilation; lower temperatures are typical in winter.

　　III. Critical Temperature Control Points

　　To ensure safe operation, dry-type transformers require temperature monitoring and protection devices, with typical control thresholds as follows:

　　80℃: Automatic shutdown of cooling fans (energy-saving mode).

　　100℃: Activation of forced-air cooling (preventing further temperature increases).

　　130℃: High-temperature alarm activation (prompting operational staff to inspect load or cooling systems).

　　150℃ (Grade F) or 180℃ (Grade H): Over-temperature trip (cutting off power to avoid equipment damage).

　　IV. Temperature Rise Calculation and Operational Management

　　Temperature rise refers to the difference between transformer temperature and ambient temperature and must be strictly controlled within allowable limits:

　　Calculation Formula: Temperature rise = Winding temperature - Ambient temperature

　　For example, a Grade F transformer operating in a 40℃ environment has a maximum allowable winding temperature of 155℃ (100℃ temperature rise + 40℃ ambient temperature).

　　Seasonal Management: Reduce load or enhance cooling in summer; increase load capacity appropriately in winter.

　　Long-Term Operation Recommendations: Lower temperatures are preferable to extend insulation lifespan. For instance, Grade F transformers are recommended to operate below 120℃ for prolonged use.

　　V. Handling Abnormal Temperatures

　　If temperatures remain abnormally high, immediate troubleshooting and corrective actions are required:

　　Check Load: Verify for overload conditions and adjust load distribution accordingly.

　　Clean Cooling Channels: Dust accumulation or blocked vents impair cooling efficiency.

　　Verify Temperature Control Devices: Ensure temperature sensors and protection circuits function correctly.

　　Contact Suppliers: If issues persist, engage professionals for inspection or component replacement.