一起励磁涌流引起后备保护误动作的分析及探讨

Analysis and Discussion on a Maloperation of Transformer Backup Protection Caused by Inrush Current

摘要: 分析了一起220 kV新建变电站变压器投产空充过程中励磁涌流引起后备保护误动的实际案例，建立了变压器空载合闸的等效电路模型，推导了变压器磁通微分方程并阐述励磁涌流产生的机理，分析了影响涌流幅值和衰减的因素，得出了励磁涌流衰减较慢时可能会引起变压器后备保护误动的结论。该结论得到了实际录波数据的验证，针对性地提出了后备保护增加励磁涌流判据和电压闭锁条件、合理安排系统运行方式来避免励磁涌流衰减过慢等应对措施。

Abstract: In order to study the effect of inrush current to the backup protection of transformer, a maloperation of transformer backup protection is presented in this paper, which is caused by inrush current emerged during the no-load switching of the new transformer in a 220 kV substation. The equivalent circuit model of the no-load switching transformer is established which derives the differential equation of the transformer magnetic flux. The mechanism of inrush current and the factors related to amplitude and attenuation are analyzed. Then some conclusions are presented. The theoretical results are verified by the real fault recorder data. According to the slow attenuation of inrush current, some measures are proposed to avoid the maloperation of backup protection, which have been verified in practice.