Study on the Effect of Harmonic Current on the Vibration Characteristics of Oil-Immersed Transformer

With the rapid development of power system and the application of new electrical equipment, the harmonic problem of power system is becoming more and more serious. In order to study the influence of harmonic current factors on the vibration characteristics of oil-immersed distribution transformers, this paper proposes a vibration simulation calculation method for the body of oil-immersed transformers based on Comsol Multiphysics finite element software. Taking the oil-immersed transformer model SFSZ11-25000/110 as the research object, firstly, the structure and vibration mechanism of the power transformer are analyzed theoretically and the equivalent mathematical models of transformer winding and core are established respectively. Then, based on the geometric model and internal structure of the oil-immersed transformer, we modeled the solid model and analyzed the influence of harmonic current on the vibration acceleration and stress field of the transformer based on the multi-physical field coupled vibration model of electric-magnetic-structural force field. The analysis results show that the average flux density of the transformer core increases slightly with the increase of superimposed harmonic current content, but the increase of the average flux density of the core is not significant with the increase of the harmonic current frequency. At the same time, the transformer winding current changes significantly after the injection of harmonics, and the effective acceleration of the transformer winding increases gradually with the increase of the superimposed harmonic current content and harmonic frequency, and the stress on it increases by two orders of magnitude compared with the fundamental wave condition.