基于波形分区重构的变压器励磁涌流与故障电流识别方法

An Identification Method of Inrush Current and Fault Current Based on Waveform Partition and Reconstruction

励磁涌流是影响差动保护正确动作率的重要因素,在电力变压器中时常发生,而大故障电流导致的电流互感器饱和也会对差动保护造成影响。为了提高差动保护的可靠性,该文提出一种基于波形分区重构的变压器励磁涌流与故障电流识别方法。首先分析了变压器励磁涌流和电流互感器饱和的波形特性,提出了将差动电流分区和重构的思想。基于此,采用小波系数能量与二阶导数能量作为联合判据,将差动电流划分为线性区和饱和区并重构。然后根据波形趋势构造了幅值的绝对值之比,利用该比值决定判断变压器是否发生了故障。最后,通过大量的仿真测试、各场景下的波形分析以及与传统方法的对比,证明了所提方法的有效性、优越性。

Inrush current often occurs in power transformers and it is an important factor affecting the correct operation rate of differential protection. What’s more,the saturation of the current transformer(CT)caused by a large fault current also affects the differential protection. In order to improve the reliability of transformer differential protection,this paper proposes an inrush current and fault current identification method based on waveform partition and reconstruction. Firstly,the waveform characteristics of inrush current and fault current with CT saturation are analyzed,and the idea of partition and reconstruction of differential current is raised. Based on this idea,the differential current is divided into the linear region and the saturation region and reconstructed by using wavelet coefficient energy and second derivative energy as a joint criterion. Next,the absolute value ratio of the amplitude is constructed according to the waveform trend,and the ratio is applied to determine whether the transformer is fault or not.Finally,through a large number of simulation tests,waveform analysis in various scenarios, and comparison with the traditional method,the effectiveness and superiority of the proposed method are verified.