A Framework for Assessing Harmonic Effects on Transformers under Various Loading Conditions

The presence of harmonics in power networks has detrimental effects on transformers, such as increased losses, heat generation, and accelerated aging of insulation, reducing their life. To effectively monitor aging and remaining service life, transformer hot spot temperature is commonly used to calculate aging acceleration rates. This paper proposes a framework that examines the impact of harmonics on transformers by assessing capacity reduction and life reduction. The framework utilizes the IEEE thermal model to analyze harmonics influence and emphasizes the importance of considering various loading conditions, including climate and operation. Simulation results on a transformer feeding a six-pulse converter and a real distribution network reveal that harmonics significantly decrease the maximum permissible load and transformer life. Neglecting different operating conditions can lead to erroneous results and incorrect decisions concerning transformer operation. Therefore, the presented framework provides a comprehensive approach to address this issue.