the
transformer body should do the drying process under the following situations:
（1） after the change of winding or insulation.
（2） the result of the insulation test: the absorptance R60/R15 is less than 1.2 hour, ir the insulance ability drops greatly.
（3） the
transformer body exposed to the air for too long a time after core suspended, or excced the regulated time (12 hours in the humidity environment, and 16 hours in the dry air).
it should pay attention to the following when doing the drying process：
（1） winding average temperature should no higher than 95℃ when heating, and the upper oil temperature should no higher than 85℃ when doing the oil dreying.
（2） when doing the heating and dreying, it should measure the temperature, winding insulance and the oil withstanding pressure intensity of all parts every 2 or 4 hours to regulate the heating temperature, it can stop the drying process if the insulance continously rise and remian stable for 6hours.
（3） if possible, the tank can apply the insulation layer and equiped with the fire unit (FU).
（4） There should be exhaust passage to exclude the moisture produced during the process of drying.
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