基于环流相似度的变压器零模涌流识别与零序保护方法

A Zero-Mode Inrush Current Identification and Zero-Sequence Protection Method for Transformers Based on Circulation Similarity

随着我国电力系统规模的扩大和输电容量的增加,Yd连接的高阻抗变压器得到了广泛应用。传统的变压器零序差动保护采用二次谐波比进行涌流制动,但该方法在空投于内部故障时会出现拒动情况。提出了一种基于环流相似度的变压器零模涌流识别与零序保护方法,该方法计算原方零模涌流和副方环流的波形相似度,再根据变压器三相的饱和系数识别内部故障,综合实现变压器准确的涌流闭锁。仿真和实验结果表明,所提保护方法在变压器和应涌流及空投于内部故障情况下均能正确动作。

With the fast expansion of China’s power system and the rapid increase of transmission capacity,Yd-connected high�impedance transformers are widely used.The traditional transformer zero sequence differential protection adopts the second harmonic ratio for inrush identification,but this method often malfunctions energizing on internal faults.In this paper,a zero-mode inrush identification and zero-sequence protection method for transformers based on circulation similarity is proposed,which calculates the waveform similarity between the primary zero-mode inrush and the secondary circulation,and then identifies internal faults based on the saturation coefficients of the three phases of the transformer,and comprehensively realizes the accurate inrush current blocking of the transformers.The simulation and experiment results show that the proposed protection method can correctly operate under the conditions of transformer energizing under sympathetic interaction and on internal faults.