基于FSAD及非周期分量的励磁涌流鉴别算法

A Algorithm to Identify Magnetizing Inrush Current Based on FSAD and Aperiodic Components

随着大型变压器容量的不断增大、变压器饱和磁通的逐渐降低以及直阻实验时所产生的剩磁不能完全消除,使得变压器有可能产生超饱和现象。在该状态下,变压器有可能产生趋于正弦波型的励磁涌流,二次谐波含量很低,间断角很小,使得基于二次谐波制动理论与基于间断角闭锁理论的差动保护无法正常工作。在推导出励磁涌流数学表达式及对超饱和现象产生机理详细分析的基础上,提出一种基于基波相位的2倍与二次谐波相位之差(FSAD)及非周期分量的励磁涌流鉴别算法。相比先前的涌流鉴别方法,该方法能迅速鉴别出超饱和态涌流,且能够在变压器内部故障时使得保护具有较快的动作速度。动模实验验证了该方案的有效性及优越性,在变压器发生超饱和,二次谐波含量小于8%的情况下,算法依然可以可靠闭锁差动保护。

With the increase of the capacity, the saturation magnetic flux of the transformer decreases. Meanwhile, the residual magnetism caused by DC resistance test cannot be eliminated completely. Consequently, the ultra-saturation phenomenon of the transformer may occur. Under this condition, the inrush waveform is similar to the sinusoidalwaveform. Hence, the second harmonic and the dead angle of the inrush are very small, which would make the differential protection based on the second harmonic or dead angle blocking cannot operate normally. The expressions of the inrush are derived firstly, and the generating mechanism for the ultra-saturation phenomenon is then analyzed. Based on it, a novel identification method of the inrush based on fundamental harmonic and second harmonic angle difference （FSAD） and aperiodic component is proposed. With the comparison with conventional identification methods, the novel approach can identify the ultra-saturation inrush quickly and correctly. Accordingly, it can make the protection have a faster operation speed when the transformer has internal faults. The dynamic experiment demonstrates the effectiveness and advantage of the proposed identification method. The algorithm can block the differential protection reliably when the transformer is in ultra- saturation condition and the second harmonic component is less than 8%.