Effects of voltage harmonic on losses and temperature rise in distribution transformers

The effects of harmonic pollution in the power system on distribution transformer losses and temperature rise have become an increasing concern. The pollution can be in the form of current and/or voltage harmonics present in the supply networks. Since the impact of voltage harmonics has hardly been investigated, this study examines the effects of distorted voltage excitation on oil-filled distribution transformers. Short-circuit and open-circuit tests were conducted on two distribution transformers. The results revealed significant increase in both losses and temperature. An equation is developed to quantify the power loss. This study also derives an equation to evaluate the resistance corresponding to the eddy-current loss.

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