大型变压器直流偏磁下电磁振动特征研究

Research on Electromagnetic Vibration Features of Large-scaled Transformer Under DC Bias

为准确掌握直流偏磁下电力变压器铁心的振动特性,文中通过建立变压器电磁—结构多物理场耦合有限元分析模型,计算了变压器直流偏磁前后铁心磁通密度分布和励磁电流,分析了麦克斯韦力和磁致伸缩力作用下不同直流偏磁时的铁心振动特征,定义了S变换相对能谱熵来描述变压器铁心振动随直流偏磁程度的变化规律。对某500 kV三相五柱式自耦变压器的仿真计算结果表明,随着直流电流增加,变压器铁心振动幅值增大,振动频谱分量增多,但随后呈现饱和趋势,且铁心心柱和旁柱振动信号的S变换相对能谱熵变化各异。研究结果可为变压器直流偏磁耐受能力评估提供重要依据。

For accurate mastering the vibration features of power transformer core under DC bias,the magnetic flux density and excited current of core before and after DC bias of the transformer is calculated by way of setting up electromagnetic-structure multi-physics coupling model finite element analysis model of transformer.The vibration feature of core at different DC bias under the action of the Maxwell force and magnetostrictive force generated are analyzed.The S transform relative energy spectrum entropy is defined to describe the variation tendency of core vibration of transformer with degree of DC bias.The simulation results of a 500 kV three-phase five-column auto-transformer show that,with the increase of DC current,the vibration amplitude of iron core and the vibration frequency spectrum components increase,but later on it shows saturation trend.The S transform relative energy spectrum entropy of the vibration signals of the core column and side column are different.The research results can provide an important basis for the assessment of transformer DC bias tolerance.