Abstract :
TOP OIL temperature and winding temperature, where the heating is caused by resistance, are determined by direct measurements when a heat run is made on a transformer in accordance with the American Standards Association Test Code for Transformers.1 However, the average oil temperature is not directly measureable. The Test Code states that the average oil temperature may be approximated by subtracting one-half of the tank temperature gradient (as determined by measurement of the temperature at the top and bottom surfaces of the external cooling means) from the top oil temperature.
