The air cooler reduce the working temperature of the transformer, high temperature will reduce the transformer's life, and even make insulation overheating, aging, then the transformer will be damaged. The air cooler which is forced oil circulation in transformer outdoor in substation has been monitored. The real-time monitoring of 24-hours indicates that the temperature changes in the range of 3 degrees C. The ambient temperature is lower than the temperature of fan about 1 degrees C. At the long-term of 479 days, the average daily temperature range of fan is 35.32 degrees C, the maximum temperature is 50.25 degrees C on August 18,2011, and the maximum temperature is 14.93 degrees C on January 17, 2011. The daily average of ambient temperature range is 37.59 degrees C, the maximum temperature is 51.16 degrees C on August 17, 2011,and the minimum temperature is 13.57 degrees C on January 17, 2011. The maximum difference between the temperature of fan and the ambient temperature is 12.48 degrees C on September 15, 2011. According to the relevant standards and monitoring results, the maximum threshold of fan temperature is defined to 80 degrees C, and the threshold of temperature rise is 20 degrees C.
