3-D FEM Analysis of Loss and Temperature Distribution in Steady State for 550kV Oil Immersed Current Transformer

High voltage (HV) current transformer with oil-impregnated paper insulation is one of the most important electrical apparatus in power substation, where the temperature distribution as well as maximum hot-spot temperature have significant impacts on its long-term safe operation. In the current work, the loss and temperature distribution of 550kV inverted current transformer with oil-impregnated paper insulation are investigated by three-dimensional (3-D) finite element method (FEM) and computation. The electro-magnetic-thermal field coupling model is designed according to the rated operation condition. The computational results show that the Joule loss of conductive rod on the primary side is 180W which is the main heat source of the transformer in rated operation. The dielectric loss of insulating layer and the eddy current loss of cores are 63.2W and 69.3W, respectively, which cannot be ignored. The hot-spot temperature of current transformer is near the core. And the maximum temperature rise is obtained as 31K relevant to the rated current of 4000A.