The hot spot temperature of a transformer is one of the critical indicators reflecting its operating status. Accurate and fast calculation of hot spot temperature is significant for the online monitoring of transformers. Considering the low computational efficiency of the transformer’s numerical full model (FM)

this paper presents a model simplification method based on the equivalent thermal parameters of windings to expedite hot spot temperature computation. Initially

the representative volume element (RVE) reflecting the periodic structure of windings is selected to formulate a reduced model (RM) for the transformer. Subsequently

to achieve equivalence between the RM and the FM

the equivalent thermal parameters of the RVE are calculated

containing the equivalent thermal conductivity (ETC)

the equivalent density (ED)

and the equivalent specific heat capacity (ESHC). Finally

the validity of the RM is verified by the temperature rise test. The results show that

compared with the tested data

the maximum error of the hot spot temperature calculated by the RM is 2.56 K

demonstrating the accuracy of the hot spot temperature calculation by the RM. Compared with the FM

the computing time of the proposed RM is reduced to 1/189

which significantly improves the computational efficiency.