Summer has come, as factory management friends, you have not encountered the dry transformer temperature overshoot? What to do when the temperature of dry transformer exceeds the standard? What are the consequences? How to prevent transformer temperature overshoot? The following billion electric with you know how to solve transformer temperature overshoot.
At present, China's dry-type transformers are classified into insulation grades, including (A), (E), (B), (F), (H) and (C) :
Maximum permissible temperature: class 105 (A), class 120 (E), class 130 (B), class 155 (F), class 180 (H), class 220 (C).
Winding temperature rise limits: 60 (A), 75 (E), 80 (B), 100 (F), 125 (H), 150 (C).
Normally operating dry transformer (class A) temperature reaches 95℃, is considered high. If the transformer is always loaded at about 60% and the temperature is about 75℃, the main reason is that the cooling fan is broken and cannot be forced to dissipate heat. The temperature rise of low-voltage equipment is generally required not to exceed 60℃ (i.e., ambient temperature +60℃). High temperature will accelerate the aging of insulation and shorten the service life of equipment. The limit is 125K for class H insulation.
According to the national standard "dry-type transformer" gb6450-1986, the limit of temperature rise of dry-type transformer has been stipulated: for the coil of dry-type transformer, the maximum temperature rise should be less than 60K when the ultimate working temperature is 105℃ when the a-class insulation material is used. When E class insulation material is used, the maximum temperature rise should be less than 75K when its ultimate working temperature is 120℃. When B class insulation material is used, the maximum temperature rise should be less than 80K when its ultimate working temperature is 130℃. When F class insulation material is used, the maximum temperature rise should be less than 100K when its ultimate working temperature is 155℃. When H class insulation material is used, the maximum temperature rise should be less than 125K when the ultimate working temperature is 180℃. When c-grade insulation materials are used, the maximum temperature rise should be less than 150K when the ultimate operating temperature is 220℃. At present, most dry transformers are insulated with h-class material, so it is generally said that the temperature of dry transformers should be below 180℃ (the transformer in the field is F grade). The theoretical maximum temperature can reach 155℃.
If the transformer runs for a long time under the condition of high temperature, it will shorten the life of the insulation board inside, make the insulation board become brittle, easy to break, lose the insulation function and cause the breakdown and other accidents. Winding insulation aging seriously, and accelerate the deterioration of insulation oil, affect the service life. So can avoid high temperature to avoid as far as possible, really not, time should not be too long.
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