直流偏磁对计量用电流互感器的性能影响分析

Analysis of Influence of DC Bias on Instrument Current Transformer

通过电流互感器(current transformer,CT)的T型等效模型推导出了计量用CT的误差与铁芯磁导率之间的关系,并通过铁磁性能实验得到了在直流偏磁下电感与铁芯磁导率之间的变化规律。设计交直流混合实验方法模拟真实的直流偏磁现象,通过实验数据分析直流偏磁对计量用CT误差的影响。结果表明,直流偏磁没有改变铁芯饱和特性,随着直流偏置量的增加,比差整体往负方向偏移,角差整体往正方向偏移,CT二次侧的谐波分量增加,偶数次谐波分量的增加尤为明显。

The relationship between the error of instrument current transformer （CT） and its core permeability is derived by T-shaped equivalent circuit based model of CT, and through experiments of ferromagnetic performance the variation law of the relationship between inductance and core permeability of CT under DC bias is attained. An AC/DC hybrid test method is designed to simulate actual DC bias phenomenon, and based on the test data the influence of DC bias on the error of instrument CT is analyzed. Analysis result show that DC bias does not affect the saturation characteristic of the core, and with the increase of DC offset the ratio error curve of CT overall shifts to negative direction while the phase angle error curve of CT overall shifts to positive direction, and the harmonic components at the secondary side of the CT increase, in which even harmonic components increase obviously.