Electromagnetic and Mechanical Characteristics of Transformer under Multiple Short-Circuit Impacts

The short-circuit withstand capability of the transformer is crucial to the reliability of power systems. Research on the short-circuit characteristics of windings is the basis for improving the stability of power transformers. Although many studies focus on electromagnetic force and cumulative deformation of two-winding transformers, there is a lack of careful comparison of the electromagnetic and mechanical characteristics of three-winding transformers, as well as the cumulative effect of stress, displacement and strain. In this paper, the model is established to study temporal response and spatial distribution of the electromagnetic and mechanical properties under short-circuit impacts. The results show that the short-circuit effects on medium and low-voltage windings are more severe than on high-voltage windings. The first current peak will lead to the greatest threat. Second, the influences of iron core and pre-stress on short-circuit characteristics are investigated. The characteristics of windings differ between inside and outside the iron core window, which is pronounced for high-voltage winding. Besides, the greater pre-stress is not better for the stability of windings. Finally, it is found that the residual stress and displacement continue to accumulate and the plastic strain appears under multiple short-circuit impacts. This work is helpful for the analysis of short-circuit withstand capability of transformers. (C) 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.