An improved dynamic model of transformer hot spot temperature based on top oil temperature

The winding hot spot temperature of the oil-immersed power transformer is an important parameter.It has a great influence on the transformer insulation aging and a close relationship with the transformer top oil temperature.The changes of non-linear thermal resistance,open-circuit impedance,and oil viscosity and winding losses with temperature are also taken into account.An improved model added on the transformer top oil temperature to calculate transformer winding hot-spot temperature by using the viscosity and loss correction factors is proposed.Model parameters are estimated by Levenberg-Marquardt method.In the end,by comparing with the measured data tested under different conditions,the model shows good consistency under underload(90%),rated load(100%) and overload(110%) conditions respectively,and describes the temperature variation more accurately in the dynamic loading profiles.