Influence of Frequency Components of Short-Circuit Electromagnetic Force on Vibration Characteristics of Power Transformer Windings

Abstract

The safe operation of power transformers is critical for the stability of power grid. The external short circuit is one of the major threats of the transformers. When an external short circuit occurs, the transformer windings would endure large electromagnetic force and vibrate violently. Accurate calculation of winding vibration is necessary for better designed windings with improved mechanical and insulation strength. The short-circuit electromagnetic force consists of DC component, fundamental frequency component and double frequency component. Different frequency components have different amplitudes and produce different displacement and stress distribution in the windings. In this paper, the influence of frequency components on vibration characteristics is investigated. The displacement distributions under the effect of different components are obtained. According to the results of the case study, it is worth to notice the influence of the fundamental frequency component on the short-circuit vibration process. For the spatial distribution, the amplitudes of vibration parameters are larger at certain positions, which implies that more attention should be paid to these positions in order to improve reliability of power transformers. The distribution characteristics are in accordance with the mode shape theory.