500kV电力变压器直流偏磁故障分析

Analysis of DC bias fault of the UHV power transformer

针对电力变压器发生直流偏磁的现象,采用ANSYS软件研究其内部磁场和励磁电流的畸变率变化情况。为分析某电厂变压器所受到的影响,该文建立大型电力变压器的二维瞬态场数学模型。在考虑到初始条件和边界条件下,利用场路耦合有限元法研究变压器在不同直流入侵后铁心内部磁场的变化,并且计算不同直流偏磁下励磁电流的总谐波畸变率。理论分析和仿真结果表明:变压器铁心饱和程度随着直流偏磁的增大而增大,励磁电流谐波量也随之增加,畸变率也越来越大。

The magnetic field and the distortion rate of exciting current are studied adopting the software ANSYS in illusion to the phenomenon of DC bias of power transformer. A 2D transient mathematical model of＇ large power transformer is proposed in this paper for the analysis of generator transformer. The change of transformer magnetic field under DC bias is studied adopting field-circuit coupling FEM under the consideration of initial and boundary conditions. And the change of exciting current harmonic current is calculated under different DC bias. The results of theory analysis and simulation show that the transformer saturation degree, the content of exciting current harmonic and the distortion rate of exciting current harmonic are increased with the increase of DC current.