According to the thermal process of transformer core and winding

this paper analyzes the compositions of core loss and load loss and their impacts on top oil temperature and hot-spot temperature of a transformer

and discusses the physical meanings of the parameters of the hot-spot temperature calculation equation recommended in the standard GB/T 15164-1994（loading guide for oil-immersed power transformers）.Moreover

the winding temperature exponent and oil temperature exponent of the recommended equation are corrected so that the physical significances corresponding to those items are more reasonable.The comparison results between the recommended equation and the improved equation indicate that the hot-spot temperature trends to being similar with small difference

and the improved equation shows higher reliability in security.