Abstract：Harmonic loss is one of the main causes of safety accidents in excitation transformers. If the loss

value is too large，it can easily affect normal substation and transmission. Therefore，a method based on wavelet

packet decomposition and reconstruction was proposed to calculate the additional loss of rectification harmonics in

excitation transformers. By obtaining wavelet packet decomposition and reconstruction coefficients，the additional

losses of two types of harmonics in excitation transformers were analyzed. The open circuit and short circuit

experiments were used to obtain the equivalent circuit parameters of the excitation transformer，and the wavelet

packet decomposition and reconstruction algorithm was used to calculate the resistance and reactance under

different harmonic frequencies，and compare them with the reference value to obtain the additional loss value of the rectification harmonic of the excitation transformer. Finally，a certain type of excitation transformer was selected

and used the proposed method to calculate its additional loss value under different harmonic frequencies. The

results show that the calculated loss value is very close to the actual results，verifying the high practical value of the

proposed method.

      Key words：wavelet packet decomposition and reconstruction；rectification harmonic；calculation of additional

losses；excitation transformer；equivalent circuit parameters；nonlinear load