Transformer Cooling Equipment Has Optimum Operating Conditions [includes discussion]

Transformer cooling equipment should be operated for maximum utilization of both the transformer and its cooling equipment. The term "transformer cooling equipment" refers in particular to the auxiliary fans that are applied to transformer radiators for cooling the radiator tubes. Many power transformers use auxiliary cooling fans to obtain increased ratings. It is desirable to operate these fans only when load and temperature conditions require the additional cooling. This is accomplished by automatic control of the fans from the transformer oil or winding temperature. This paper discusses the methods for obtaining satisfactory control of the cooling fans on oil-immersed air-cooled/forced-air-cooled (OA/FA) and oil-immersed air-cooled/forced-air-cooled/forced-air-cooled (OA/FA/FA) transformers only. The fans are considered to be actuated by a thermal image device simulating winding hot-spot temperature. The resulting conclusions apply only to the use of fans as auxiliary cooling equipment.