The Evaluation of Transformer Lifespan Under Nonlinear and Unbalanced Loads

Authors: Büşra Nur Emre, Güven Kömürgöz Kırış

Abstract:

In recent years, the widespread use of electronic devices has led to a significant increase in nonlinear loads in power systems. These nonlinear loads generate harmonics, which degrade power quality and adversely affect the operation of transformers. Harmonic currents produced by nonlinear loads cause additional losses, leading to issues such as derating, overheating, and even transformer failures. Overheating, particularly the rise in hottest spot temperature during operation, is a critical consequence of harmonics. The hottest spot temperature is one of the most important factors influencing the operational lifespan of transformers. In this study, the additional load losses caused by nonlinear loads on transformers are analyzed. Following the analysis of these losses, their impact on the transformer hottest spot temperature and overall lifespan will be investigated. The study utilizes data from three-phase 6 MVA transformer with varying phase currents and harmonic content across the phases. The findings aim to provide insights into how harmonics exacerbate losses and thermal stress, ultimately affecting transformer performance.

Keywords: Harmonics, harmonic loss factor, hottest spot temperature, k-factor, transformers.

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