Winding Temperature indicator (WTI) :
1.The thermometer bulb is located in a pocket near the winding The bulb is surrounded by hot circulating oil. The bulb is also heated by central heater
2.The heat given to the bulb is a function of load current as well as temperature of oil near winding
3.The device is matched with the heating curve of the transformer winding
4.The reading of hot spot thermometer is related to actual thermal condition of transformer than that of oil temperature indicator.
