Investigation on impact of current harmonic contents on the distribution transformer losses and remaining life

Transformers are one of the main equipments of distribution systems. Increase in transformer loss is mostly the source of the damages, and caused by increased harmonic contents, especially current harmonic. These losses will result in an increase in temperature of various parts of transformer, especially its hot-spot temperature, and this temperature increase leads to insulation life reduction. Therefore, it seems necessary to know the harmonic orders and estimate hot-spot temperature of the transformer, which can help predicting the remaining life of the transformer. In this paper, relations associated with transformer life and losses are reviewed. The equivalent losses and capacity of a typical distribution transformer have been evaluated using simulation in MATLAB/SIMULINK based on its model under harmonic condition. Then, hot-spot temperature and remaining life of the transformer are estimated. In addition, the transformer has been simulated using Finite Element Method in MAXWELL software. Finally, results are discussed and compared.