Evaluation of Distribution Transformer Losses and Remaining Life considering Network Harmonic, Based on Analytical and Simulation Methods

Transformers are one of the main parts of power systems and their damages can cause serious harms to the system. 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 brings about insulation life reduction. Therefore, it seems necessary to know the harmonic orders and decrease in transformer loading capacity, and calculating hot-spot temperature of the transformer, which can help predicting the remaining life of the transformer. In this paper, relations associated with transformer losses and life assessment are reviewed and analyzed. The equivalent losses and capacity of a typical 15 KVA single phase transformer is evaluated using analysis and simulations in MATLAB/Simulink-based on a valid model of transformers under harmonic condition. Also, hot-spot temperature and remaining lives of the transformer are estimated based on a MATLAB written algorithm. Finally, results are compared.