中文摘要：

变压器中性点流入直流电流时,在变压器内部会产生直流偏磁现象.单相变压器具有独立的磁回路,因此磁阻比较低,较小的直流电流就可以引起磁饱和,直流偏磁现象在单相变压器内部产生的影响比较明显,因此文中基于场路耦合有限元法,对一台容量为240 MVA的单相电力变压器在不同直流偏磁水平下的空载运行状态进行了仿真计算,分析了直流偏磁量对变压器励磁电流波形、谐波含量以及磁场分布的影响规律.在此基础上建立了变压器铁心的多物理场耦合有限元模型,对铁心在直流偏磁前后的振动噪声进行了对比分析,并提出通过分析变压器所允许的最大声压级,来预估产品所能承受的最大直流量,对变压器的结构设计具有一定的指导意义.

英文摘要：

Direct-current （DC） magnetic bias is generated when DC flows through neutral point of a transformer..The reluctance is low since single-phase transformer has independent magnetic path,and little DC will consequently give rise to magnetic saturation,thus DC magnetic bias is manifest in single-phase transformer.A 240 MVA single-phase transformer is treated as an example,on the basis of field-circuit coupled finite element method,and no-load characteristics are simulated with diverse DC magnetic bias.The influence of DC magnetic bias on the waveforms of exciting current,exciting current harmonic component and the magnetic distribution are analyzed.On the basis of above work,the multi-field coupling finite element analysis model is established,and core＇s vibration noises with and without DC magnetic bias are compared and analyzed.Meanwhile,it is proposed that the maximum feasible noise is utilized to estimate the maximum DC component that transformer can stand,which is of certain guiding significance for the structure design of single-transformer.